GEOLOGICAL SURVEY CIRCULAR 799-A,B 

Earthquake Activity and Quaternary Deformation 

of the Western Transverse Ranges, California 

Recent Earthquake Activity and Focal Mechanisms 

in the Western Transverse Ranges, California 

Late Quaternary Deformation in the Western 

Transverse Ranges, California 

To accompany U. S. Geological Survey 

Miscellaneous Field Studies Map MF-1032, 

by R. F. Yerkes and W H. K. Lee 

Earthquake Activity and Quaternary Deformation 

of the Western Transverse Ranges, California 

Recent Earthquake Activity and Focal Mechanisms 

in the Western Transverse Ranges, California 

By W. H. K. Lee, R. F. Yerkes, and M. Simirenko 

Late Quaternary Deformation in the Western 

Transverse Ranges, California 

By R. F. Yerkes and W. H. K. Lee 

GEOLOGICAL SURVEY 

To accompany U. S. Geological Survey 

Miscellaneous Field Studies Map MF-1032, 

by R. F. Yerkes and W H. K. Lee 

CIRCULAR 799-A,B 
United States Department of the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. William Menard, Director 

Library of Congress catalog-card Number 79-600024 

Free on application to Branch of Distribution, u.s. Geological Survey,l200 South Eads Street, Arlington, VA 22202 
Recent Earthquake Activity and Focal Mechanifms 

in the Western Transverse Ranges, California 

By W. H. K. Lee, R. F. Yerkes, and M. Simirenko 

EARTHQUAKE ACTIVITY AND QUATERNARY DEFORMATION OF THE WESTERN 

TRANSVERSE RANGES, CALIFORNIA 

GEOLOGICAL SURVEY CIRCULAR 799-A 

CONTENTS 

Page 

IntDDduction-----------------------------------------------------------

Previous investigations-------------------------------------·----------- I 

Seismograph stations--------------------------------------------------- 3 

Routine data processing and analysis----------------------------------- 3 

Relocation of 1970-75 earthquakes-------------------------------------- 6 

Earthquake hypocenters and their accuracy------------------------------ 7 

Distribution of earthquake hypocenters--------------------------------- 7 

Earthquake focal mechanisms-------------------------------------------- 9 

Discussion------------------------------------------------------------- IO 

References cited------------------------------------------------------- I4 

ILLUSTRATIONS 

[Plates published separately as u.s. Geological Survey Miscellaneous Field 

Studies Map MF-1032] 

Plate 1. 

2. 

Figure 1. 

2. 

3. 

4. 

5. 

6. 

7. 

Maps showing faults and epicenters of 1970-75 earthquakes and 

location of seismograph stations. 

Maps showing faults and focal depths of 1970-75 earthquakes and 

focal mechanisms of selected earthquakes. 

Page 

Map of southern california showing epicenters of earthquakes 

of magnitude 6 and greater since 1912----------------- 2 

Cross-sectional plots of hypocenters along line A-A'------- 8 

cross-sectional plot of hypocenters along line B-B'-------- 9 

Cross-sectional plot of hypocenters along line C-C'-------- 9 

Cross-sectional plot of hypocenters along line D-D'-------- 9 

Fault-plane solution based on ccroposite first notions of 

10 earthquakes in Santa Barbara Channel--------------- IO 

Diagrams showing fault-plane solutions based on first 

notions of selected earthquakes in the western 

Transverse Ranges--------------------------------- I2 

TABLES 

Page 

Table 1. IDeations, dates of operation, and delays of seisrrographic 

stations used in this study---------------------------- 4 

2. List of earthquakes in the western Transverse Ranges, 

1970-75------------------------------------------------ I6 

3. Criteria for detennining Q---------------------------------- 7 

4 • Data on mapped focal mechanisms----------------------------- II 

v 

Recent Earthquake Activity and Focal Mechanisms 

in the Western Transverse Ranges, California 

By W. H. K. Lee, R. F. Yerkes, and M. Simirenko 

INTRODUCTION 

The east-west-trending Transverse Ranges 

Province is a portion of the complex PacificAmerican plate toundary where tectonism has 

accelerated during late Cenozoic time, perhaps 

reaching a maxinn.mt in Quaternary time. The contemporary seismic setting of the Transverse 

Ranges in relation to the rest of southern 

california is indicated by the distribution of 

recent large earthquakes (fig. 1) . During the 

:past 60 years, 24 earthquakes of local magnitude 

6 or greater have occurred in southern california. Five of these occurred in the western 

Transverse Ranges : the Santa Barbara earthquake 

of 1925 (magnitude 6.3), the Point Arguello 

earthquake of 1927 (magnitude 7 .5), the Santa 

Barbara earthquake of 1941 (magnitude 6), the 

San Fernando earthquake of 1971 (magnitude 6.4), 

and the Point Mugu earthquake of 1973 (magnitude 

6) • 

We report here the earthquake activity in 

the western Transverse Ranges for a six-year 

period from 1970 through 1976. The studied area 

extends from lat 33°45' N. to 34°45' N. and fran 

long 118°30' E. to 120°30' E. (boxed area in 

fig. 1) . This region includes the Santa Barbara 

Channel and surrounding area, the Ventura Basin, 

and the coastal and offshore area south of the 

Santa M:mica M::>untains and the Channel Islands. 

The San Fernando earthquake sequence has 

been extensively studied (Allen and others, 1971, 

1973; 'fucker and Brune, 1973; Whitconi:> and 

others, 1973, arrong others) , and we have not 

restudied that sequence. 

Acknowledgments.~e wish to thank the 

Seismological Laboratory of the california 

Institute of Technology, Geophysical Laboratory 

of the University of Southern california, and 

the California Deparbnent of V.7ater Resources for 

making their seismic data and seisroograms available to us. We are also indebted to Jim Buik.a, 

Travis Houck, and Sharon Kirkman for assistance 

in data processing. 

PREVIOUS INVESTIGATIONS 

Reliable accounts of California earthquakes 

date from about 1800. The earliest reports are 

found in notes of Spanish explorers and early 

settlers and in the records of the Frarciscan 

missions. The earthquake history before installation of seismographs in the 1900's is summari~ 

in various reports describing earthquake effects 

such as Tatmley and Allen ( 19 39) and Richter 

(1958). Since 1932, inst.n.m'entally rec":">rded 

earthquakes throughout southern california have 

been reported by the Seismological Lal:x:rato:ry of 

the California Institute of Technology at Pasadena. Results from this seisroograph ne:twork 

have been synthesized by Allen, St. Amand, 

Richter, and Nordquist (1965) 1 who relc:ted the 

earthquake data from 1934 to 1963 to tte regional geologic structures in southern California. 

M:>re recently, earthquake data obtaineC' by the 

california Institute of Technology were: summarized systematically in Hileman, Allen, and 

Nordquist (1973) 1 Friedman, WhitCOITb, Allen, 

and Hileman (1976) 1 and Fuis, Friedman, and 

Hileman (1977) . 

Sylvester, Smith, and Scholz (197C) studied 

the earthquake swa...'YlU that occurred in the Santa 

Barbara Channel fran June 26 to August 3, 1968 1 

and discussed their results with respect to the 

seismic history of the channel and hydrocarbon 

exploration and withdrawal. An offshore oilwell 

blowout on January 28 1 1969, drew naticnal attention to the effects of oil pollution ar.d provided 

the impetus for preparing a report on the geology, 

petroleum developnent, and seismicity cf the 

Santa Barbara Channel region (U.S. Geological 

Survey Professional Paper 679) . In til at report, 

Hamil ton and others ( 19 69) reviewed the. seismicity of the channel area and its possitle associated effects on the region and noted that the 

limitations of the existing seismic network precluded identification of individual active faults 

within the channel. 

In order to improve earthquake rroritoring, 

a new network of seisrrograph stations surrounding the Santa Barbara Channel was estal: lished by 

the U.S. Geological Survey in late 1969. Lee 

and Vedder (1973) reported the earthquakes 

located by this network for 1970 and 1971 and 

showed that the earthquake activity apF<:>.ars to 

be spatially related to recognized faults in the 

region. 

On February 21, 1973, a magnitude 6 earthquake occurred in the vicinity of Point~ Mugu at 

the southeast end of the Santa Barbara Channel. 
0 T11lt1r~ 

0 100 200 

KILOMETERS 

Figure 1.--Bouthern California showing epicenters of earthquakes of magnitude 6 and gre~ter since 

1912. Area of this study sho..·m by box. Faults are sha-m by solid lines, dashed where approximately located. MJdified from Allen, St. Amand, Richter, and Nordquist (1965) . 

Ellsworth and others ( 197 3) , who reported the 

seismological investigations of this earthquake 

sequence, noted that the canplex fault zone 

associated with the southern bonnda.cy of the 

Transverse Ranges constitutes a significant 

earthquake hazard. Stiennan and Ellsworth (1976) 

found that rrost aftershocks of the Point Mugu 

earthquake clustered in a region 5 km in diameter 

centered 6 km southeast of the main shock, and 

that the strain release within the imbricate 

2 

fault zone was controlled by slip on preexisting 

planes of weakness under the influence of a compressive stress oriented northeast-southwest. 

Source parameters of the Point Mugu p.arthquake 

were estimated by Boore and Stiennan (1976) from 

strong~tion recordings at Port Hu61eme and 

Pasadena. 'iliey preferred a fault m::xlel in which 

rupture spread radially from the focal point, 

and they concluded that the area of initial rupture was smaller than the area outlined by the 
aftershock distribution. They also sho,.ved evidence that the rupture process involved a multiple earthquake. 

Castle, Church, Elliott. and Savage (1977) 

investigated elevation changes in the epicentral 

region of the Point Mugu earthquake f and found 

that between 1960 and 1968 surveys, the upper 

(northern) plate of the west-trending Santa t-bnica 

fault rose by 3 to 4 em at least as far west as 

Point Mugu, and this uplift is consistent with 

continuing thrusting along the north-dipping 

southern frontal fault systerrt of the Transverse 

Ranges. From 1968 to 1971 1 the 1960-68 verticalrrovEroent pattern was crudely reversed in both 

form and magnitude, a feature suggesting leftlateral reverse creep at depth and (or) onset of 

dilatancy. Between 1971 (pre-eart..""lquake) and 1973 

(post-earthquake), the upper plate of the Santa 

Monica fault underwent uplift that nearly restored 

the 1971 surface to its 1968 configuration. Because the observed rebound during 1971-73 is 

approximately an order of magnitude greater than 

the coseismic uplift calculated from dislocation 

modeling, Castle, Church, Elliott, and Savage 

(1977) concluded that this 1971-73 uplift might 

have been mainly preseismic and perhaps indicative 

of an evolving dilatant volume. The question of 

dilatancy before the Point Mugu earthquake was 

studied by Stewart (1973) using seismic arrival 

times. 

In an environmental impact study of oil and 

gas development on the outer continental shelf in 

Santa Barbara Channel ( 0. S. Geological Survey, 

1975), w. H. K. Lee and W. L. Ellsworth reviewed 

the earthquake history in same detail and prepared 

an extensive list of significant felt earthquakes 

for the period fran 1800 through 1973. They concluded that the maximum credible earthquake for 

engineering design purposes is an event of magnitude 7 . 5 occurring anywhere in the Santa Barbara 

Channel region, and they urged a rrore systematic 

and thorough study of the region with regard to 

earthquake hazards . 

SEISMOGRAPH STATIONS 

The principal data used for the present study 

carne fran the 30 telemetered seisrrograph stations 

operated by the U.S. Geological Survey in and near 

the western Transverse Ranges (pl. 11 ) • These 

stations were supplEmented by 18 tEmporary stati.on.s 

operated by the U.S. Geological Survey for two 

nonths after the 1973 Point Mugu earthquake. In 

addition, we made use of arrival times recorded by 

seisrrograph stations operated by the California 

Institute of Technology, University of Southern 

California, and California Departirent of 'liiJater 

Resources whenever needed to improve earthquake 

locations. A total of 105 stations were used in 

the present study. Station data including coordinates, elevations, and dates of operation are 

Plates published separately as U.S.G.S . .Miscellaneous Field Studies Map MF-1032. 

3 

listed in table l, and station locaticns with 

respect to geographical and structural features 

are shovm in plate 1. 

The equipment at each USGS telemctered station includes a vertical-component 1-Hz seisrrometer, a package containing a preamplifier, a 

voltage-controlled oscillator, and batteries. 

The frequency-rrodulated tone produced at each 

station is carried by wire (or radio from offshore stations) to a terminal where it is combined -with tones from seven other sta t:ions. The 

resulting multiplexed signals are ther. transmitted by telephone line to Menlo Park .• Calif. 

There, the eight channels of seismic data on each 

telephone line are separated, demodulated, and 

recorded on a 16-rrm film recorder (Develocorder). 

In addition, two timing signals (radic station 

~VVB and a local time code) are recorded simultaneously with the seismic signals·. Magnification 

for individual stations is adjusted according to 

the background noise level in steps of 6 db. 

Most of the USGS seisrrograph stations are oper,ated 

at a magnification of about 100,000 at 1 Hz. As 

a backup 1 the signals transmitted on the telephone 

lines are also recorded on analog tapes. Playbacks from these tapes supplement the film recordings. 

Equipnent recording methods used by 

other institutions for their seismograph stations are similar to those used by the U.S . 

Geological Survey. In addition, the California 

Institute of Technology and the Califcrnia Department of Water Resources operated same 3-canponent stations, the records of which greatly 

facilitate the reading of S-arrivals. 

In response to the San Fernando and Point 

Mugu earthquakes , many additional seis:"""graph 

stations have been installed in southern 

California with support from the U.s. Geological 

Survey. At present, the California Institute of 

Technology, U.S. Geological Survey, University 

of Southern California 1 and California Department of Water Resources operate aver 210 seisrrograph stations in southern California. 

ROUTINE DATA PROCESSIJTG 

AND ANALYSIS 

The principal recordings of seisn'.ic signals from the USGS stations are 16~ films. 

The films were scanned daily to prepare a log 

of events. Earthquakes with signal durations 

of 20 seconds or greater were always t.imed. 

This duration corresponds to a magnitude cutoff of about 1-3/4. Events of less tbm 20-

second duration were timed if there w~..re three 

or more impulsive arrivals. During tb9 timing 

process, P-arrival time, first P :rrotion, Sarri val time, maximum amplitude and pe..riod, and 

signal durations were read whenever possible 

and necessary. 

The data were then processed by canputer 

to give origin time, hypocenter location, ma.gnitude, and fault-plane solution of the earthquakes. Earthquakes were located mainly on the 
Table l.--Locations, dates of operation~ and delays of seismographic stations used in this study 

Station Geographic location Elev- Delay On-date1 Off-date2 

ation1 

Inst. Code N Latitude W Longitude (rn) (s) Year Ivbnth Day Year tbnth Day 

USGS SBAI 34 0.79 119 26.23 104 0.05 1973 3 1 

USGS SBCC 34 56.48 120 10.32 610 0.23 1969 11 24 

USGS SBCD 34 22.12 119 20.63 213 0.20 1971 11 22 

USGS SBCL 34 24.75 119 21.67 177 0.04 1969 11 24 1971 11 

USGS SBLC 34 29.79 119 42.81 1190 -0.04 1969 11 11 

USGS SBLG 34 6.57 119 3.85 415 -0.11 1969 11 24 

l.1SGS SBLP 34 33.62 120 24.03 134 -0.05 1969 11 24 

USGS SBSC 33 59.68 119 37.99 457 -0.06 1969 11 24 

USGS SBSM 34 2.25 120 20.99 172 -0.03 1969 11 24 

USGS SBSN 33 14.70 119 30.40 259 -0.01 1970 3 30 

USGS CAM 34 15.27 119 1.99 271 0.20 1973 6 16 

USGS CJP 34 10.92 118 59.21 317 -0.01 1973 6 18 

USGS CLP 34 5.33 118 57.85 549 -0.17 1973 6 16 

USGS ECF 34 27.48 119 5.44 1005 0.30 1974 6 15 

USGS EGG 34 7.95 119 8.85 0.0 1973 6 16 1973 7 

l!'SGS KYP 34 6.10 118 52.77 701 -0.15 1973 6 18 

USGS OCB 34 2.20 119 1.00 -75 0.22 1973 6 18 

USGS Pill 34 0.25 118 48.37 41 0.04 1973 6 18 

USGS SAD 34 4.88 118 39.90 727 -0.15 1973 8 26 

USGS SIP 34 12.26 118 46.92 701 0.0 1973 6 18 

USGS SUF 34 24.58 119 12.15 0.39 1973 7 13 1973 8 

USGS CAS 35 55.90 120 20.22 1189 0.0 1970 12 15 

USGS GDH 35 49.86 120 21.17 433 -0.08 1968 3 21 

USGS JOL 36 5.02 121 10.15 336 0.0 1969 6 18 

USGS PKF 35 52.91 120 24.81 469 0.0 1968 1 11 

USGS PNC 36 33.73 121 38.18 305 0.0 1967 9 24 

USGS PTV 36 6.50 120 43.27 506 0.0 1970 4 16 

USGS SHG 36 24.83 121 15.22 192 0.0 1969 6 18 

USGS TAY 35 56.73 120 28.45 552 0.0 1968 1 12 

USGS WKR 35 48.87 120 30.67 503 0.21 1968 1 11 

USGS AGOR 34 9.52 118 44.52 0.07 1973 2 24 1973 4 14 

USGS CAMH 34 15.19 119 2.28 0.0 1973 2 23 1973 4 12 

USGS CLEF 34 13.07 118 54.64 0.13 1973 2 24 1973 4 12 

USGS DEER 34 4.02 118 59.20 -0.03 1973 2 23 1973 4 13 

USGS Dill1E 34 0.25 118 48.38 0.29 1973 2 12 1973 4 12 

USGS EGG F. 34 7.87 119 8.82 -0.01 1973 2 22 1973 4 13 

USGS LEMN 34 10.79 119 1.57 -0.08 1973 2 23 1973 4 13 

USGS lONG 34 19.77 118 56.82 0.0 1973 2 25 1973 3 14 

USGS MUGU 34 6.87 119 4.00 0.0 1973 2 25 1973 3 10 

USGS NIOO 34 4.45 118 40.84 -0.22 1973 2 24 1973 3 15 

USGS POI'R 34 9.37 118 59.33 0.0 1973 2 22 1973 2 25 

USGS SBOB 34 2.20 119 1.00 0.0 1973 3 29 1973 4 14 

USGS SHER 34 7.44 118 51.57 0.01 1973 2 22 1973 4 13 

USGS SIMI 34 14.81 118 48.28 0.0 1973 2 24 1973 3 14 

USGS SQPT 34 3.37 118 55.94 0.03 1973 2 22 1973 4 13 

USGS SYCA 34 8.37 118 58.06 0.0 1973 2 23 1973 4 13 

USGS TPNG 34 6.47 118 36.34 0.0 1973 2 25 1973 3 14 

USGS WIND 34 5.15 119 2.20 -0.14 1973 2 22 1973 2 25 

CIT BAR 32 40.80 116 40.30 510 0.0 1952 1 17 

CIT CIS 33 24.40 118 24.20 485 -0.06 1971 7 1 

CIT CLC 35 49.00 117 35.80 766 0.0 1949 7 8 

CIT ewe 36 26.30 118 4.70 1620 o.o 1965 10 13 

CIT FTC 34 52.40 118 53.60 990 -0.14 1952 11 21 1970 9 

CIT GLA 33 3.15 114 49.59 627 0.0 1966 12 20 

CIT GSC 35 18.10 116 48.30 990 0.0 1961 11 7 

4 
Table !.--Locations~ dates of operation~ and delays of seismographic stations used in this study--con'd. 

Station Geographic location Elev- Delay On-date1 Off-date2 

ation1 

Inst. Code N Latitude W IDngitude (m) (s) Year fv'bnth Day Year MJnth Day 

CIT HAY 33 42.50 115 38.30 439 0.0 1956 6 20 

CIT IKP 32 38.93 116 6.48 957 0.0 1972 11 8 

CIT IRC 34 23.40 118 24.00 580 0.03 1971 11 1 

CIT ISA 35 39.80 118 28.40 835 0.09 1967 4 5 

CIT LGC 33 50.15 118 9.02 17 0.0 1971 7 7 

CIT MVC 34 13.43 118 3.46 1730 0.06 1928 4 23 

CIT PAS 34 8.90 118 10.30 295 -0.05 1927 3 17 

CIT PIM 33 21.20 116 51.70 1692 0.0 1939 9 7 

CIT RIJR 33 59.60 117 22.50 260 -0.25 1926 10 19 

CIT SBB 34 41.30 117 49.50 850 0.12 

CIT SBC 34 26.50 119 42.80 90 0.17 1927 5 10 

CIT SCI 32 58.80 118 32.80 219 0.27 1971 11 11 

CIT SCR 34 6.37 118 27.25 -0.23 

CIT SCY 34 6.37 118 27.25 287 0.12 

CIT SJQ 33 37.20 117 50.70 165 0.0 1971 7 7 

CIT SJR 33 37.20 117 50.70 0.34 1971 7 7 

CIT SPH 33 44.80 118 20.08 445 0.18 1971 7 7 

CIT SWM 34 43.10 118 34.90 1220 -0.03 1966 3 7 

CIT SYP 34 31.60 119 58.70 1305 -0.13 1967 6 7 

CIT TCC 33 59.67 118 0.77 299 0.0 1971 7 7 

CIT 'I'Q\J 33 59.67 118 0.77 0.0 

CIT TIN 37 3.30 118 13.70 1195 0.0 1929 9 4 

CIT TPC 34 6.35 116 2.92 720 0.0 1972 5 5 

CIT 'IWL 34 16.70 118 35.67 390 0.05 1971 11 1 

CIT VPD 33 48.96 117 45.73 183 0.11 1971 7 7 

CIT ~VDY 35 42.00 118 50.60 500 o.o 1952 8 5 1970 p 

CIT CSRP 34 8.55 118 55.56 0.20 

CIT CVGR 34 7.46 119 7.97 0.15 

CIT CHOS 34 9.65 119 2.68 0.0 

CIT CBKB 34 4.62 118 52.80 0.0 

CIT CBSC 34 4.50 119 0.60 0.0 

~ CSP 34 17.88 117 21.45 1268 0.0 

Ca\TR CSL 34 14.94 117 16.68 1490 0.0 

CilVR MRD 34 20.57 117 14.46 975 0.0 

CI:WR PEC 33 53.52 117 9.64 616 0.34 

CI:WR PYR 34 34.08 118 44.46 1247 0.17 

UCB FRI 36 59.50 119 42.50 119 0.0 

usc BHR 34 0.51 118 21.72 0.0 

usc DHB 34 1.05 118 23.13 0.01 

usc DRP 33 46.70 118 13.00 0.0 

usc FMA 33 42.75 118 17.47 -0.10 

usc GFP 34 7.76 118 18.59 0.05 

usc HOI 33 59.64 118 22.98 o.o 

usc IPC 33 58.24 118 20.07 o.o 

usc JBF 33 59.58 118 20.68 0.0 

usc LCL 33 50.00 118 11.41 0.16 

usc I.CM 34 1.07 118 17.22 0.0 

usc LNA 33 47.35 118 3.27 0.63 

usc RCP 33 46.66 118 8.00 0.67 

usc TPR 34 5.33 118 35.20 -0.31 

1Blanks, elevation or date not known. 

2Blanks, station still active. 

5 
basis of P-arri val times fran seisrrograph stations with clear arrivals. S-arri vals were 

used to supplement the P-arrivals whenever 

possible and necessary. The HYP071 computer 

program (Lee and Lahr, 1975) was used to locate 

hypocenters, oorrpute magnitudes, and plot firstmotion patterns. This program employs Geiger 1 s 

(1912) method to dete:rmine hypocenters by minimizing ~~e residuals between observed and calculated arrivals • Travel times fran a trial 

hypocenter to the stations and their partial 

derivatives are computed on the assumption of 

a horizontal multi-layer model by a technique 

introduced by Eaton (1969). 

There are no published descriptions of the 

configuration and nature of the crust beneath 

the western Transverse Ranges as determined by 

explosion seisnology. Shor and Raitt (1958) 

interpreted the crustal structure of a part 

of the continental borderland of southern 

california by seismic-refraction methods, 

but their seismic profiles are well south of 

the Santa Barbara Channel. Although Healy 

(1963) reported several crustal models that are 

consistent with data obtained from two reversed 

seismic-refraction profiles between San Francisco and IDs Angeles , his profiles transect 

only the northeastern part of the region 

covered in the present study. 

We have adopted the four-layer model of 

Healy (1963, p. 5783) as an approximation to 

the crustal structure beneath the study area. 

This model is specified in the following table: 

Layer Depth P velocity 

(km) (km/s) 

1 0.0 to 2.6 3.0 

2 2.6 to 16.7 6.1 

3 16.7 to 26.1 7.0 

4 belo.-v 26.1 8.1 

We further assumed that the ratio of P-velocity 

to S-velocity is constant and has a value of 

1. 78. Station corrections as given by Lee and 

Vedder (1973) were used for initial location of 

earthquakes. 

Because of the difficulties in maintaining 

precise calibrations of seismograph stations, 

maximum amplitude and period were not used to 

determine earthquake magnitude. Instead, magnitudes were estimated by the signal-duration 

method introduced by Lee, Bennett, and Meagher 

(1972) . The magnitude for a given earthquake is 

the average value of magnitude estimates at 

various stations. Station magnitude (M) is derived from its recorded signal duration (1:) 

according to the formula 

M = -0.87 + 2.00 log (T) + 0.0035~, 

where ~ is the epicentral distance in kilaneters. 

6 

The signal duration is the period fran the onset 

of the first P-arrival to the point where the 

trace arnpli tude (peak to trough) falls belo.-v 1 

an as it appears on the Geotech film viewer (20X 

magnification) for seismic signals re:-:-:orded on 

16-mm Develocorder films. 

Lee and Vedder (1973) canpared rr1gnitudes 

determined by the above method with the tradll:ional local magnitudes determined by the: california 

Institute of Technology (CIT) for the: 24 earthquakes in the Santa Barbara Channel region which 

appeared in both the U.S. Geological Survey (USGS) 

and CIT 1970-71 earthquake catalogs. They concluded that the magnitude dete:rmined by USGS 

agrees well (within 1/4 unit) with t.tat dete:rmined 

by CIT, but that the USGS magnitude rr1y be systematically lower than the CIT magnitude by 0.1 unit. 

These results are remarkable because the coefficients in the duration-magnitude equction are 

those determined for central California earthquakes. 

RELOCATION OF 1970-75 

EARTHQUAKES 

Routine analysis of earthquakes in the western Transverse Ranges has been carried out using 

USGS stations. 1970-71 earthquake data for the 

Santa Barbara Channel region were published by 

Lee and Vedder (1973) . Similar data for 1972-73 

were listed in an open-file report b~' Kirkman and 

Ellsworth (1977a). For the Santa Mxrica :r.Duntains 

area, Kirkman and Ellsworth (1977b) surrmarized the 

earthquake data for the period February 21 to 

December 31, 1973; the Point Mugu earthquake 

sequence was extensively studied by Stierrnan and 

Ellsworth (1976). The 1974-75 data in the western Transverse Ranges were routinely analyzed by 

two of us (Simirenko and Lee) but we.':"e not published. 

For the present study, we starb2d with the 

routine data on file in the USGS. That list was 

combined with earthquake lists prepared independently by CIT, the University of Sout~ern California (USC), and the california Deparb:nent of Water 

Resources ( crnR) • The cont>ined list has a total 

of about 2, 000 earthquakes 1 of which 1 1 110 events 

are in or near our study area. Arrival times 

fran CIT, USC 1 and CIWR were added to the USGS 

data. Earthquakes were then located using the 

combined arrival-time data by the HY?071 program. 

A study of the results indicated that for sane 

earthquakes, certain critical statio:1S were not 

read and some stations had large residuals . We 

then reread seisrrograrns for these evr~nts at USGS, 

CIT, USC, and CrnR to correct errors and to ol::X:.ain 

arrival times that were not read routinely before. 

The horizontal multi-layer model of crustal 

structure used in earthquake locatio:-1 is inadequate to describe the complexity of the earth 1 s 

crust beneath the western Transverse Ranges. A 

standard method to improve the simple crustal 

model is to derive station correctio:'1s from earthquake P-residuals . We divided the s ':".udy region 

into areas of 5 minutes latitude by 5 minutes 
longitude and selected a sample of the bestrecorded earthquakes in these areas. These earthquakes were then used as master events in an 

iterative procedure to derive a set of station 

correction.s. The results are included in table 1. 

Ho.vever, corrections for some stations could not 

be derived for lack of data, and they were 

assumed to be zero. 

We used the station corrections derived from 

the master events to relocate the 1,110 events 

in or near our study area. We rejected 158 earthquakes that had magnitudes less than 1 and also 

rejected 322 earthquakes that were relocated outside the study area, that belonged to the San 

Fernando earthquake sequence, or had insufficient 

data for even approximate locations. This treatm=nt yielded a total of 630 adequately located 

earthquakes in the study area. A few of these 

events, ho.vever, nay be e..xplosions. 

EARTHQUAKE HYPOCENTERS 

AND THEIR ACCURACY 

The 630 earthquakes that occurred in the 

western Transverse Ranges for the six-year period 

from 1970 to 1975 are listed chronologically in 

table 2 (p.l6). Included are the origin time, location of hypoce..nter (epicenter and focal depth) , 

magnitude, and number of arrival times used. In 

addition, five parameters are listed as a means of 

evaluating the quality of hypocenter solution Q: 

(1) the largest azimuthal separation between 

stations (a) , (2) epicentral distance to the 

nearest station (S) , (3) root-mean-square error 

of the time residuals , ( 4) standard error of the 

epicenter, and (5) standard error of the focal 

depth. On the basis of these parameters, the 

general reliability of each earthquake solution 

is graded as either excellent (A), good (B), fair 

(C), or poor (D). Criteria for quality classification are listed in table 3 . 

A brief discussion of the accuracy of hypocenter solutions was given by lee, Eaton, and 

Brabb (1971). To obtain a reliable epicenter, 

the largest azimuthal separation between stations 

(a) should be less than 180° so that the earthquake epicenter is surrounded by stations. To 

obtain a reliable focal depth, epicentral distance to the nearest station (2) should be less 

than the focal depth, so that there is a direct 

ray-path. In addition, systematic er~:-ors arise 

from uncertainties in the crustal velocity Irodel. 

These errors cannot be determined without controlled experiments, such as calibrated explosions in the focal region. CMing to irregular 

distribution of stations and occasional loss of 

data from critical stations, the quality of 

hypocenter solutions in table 2 varies. Although standard erl-o~s of epicenters and focal 

depth are given, they must be interpreted with 

caution, especially for quality C and D solutions. These standard errors are corrputed with 

respect to the assumed crustal velocity Irodel, 

which is not necessarily a good approximation 

to the real earth. 

Because we do not have accurately calibrated explosions in the western Transverse Ranges, 

it is difficult to ascertain the hypocenter 

accuracy of our earthquake solutions . Extrapolation from experience in central California 

suggests that earthquake locations in the 

western Transverse Ranges are accurate to about 

5 km in general (table 3) . This conclusion is 

supported by the fact that we were able to 

locate several offshore explosions near Santa 

Cruz Island within 5 km of their approximate 

positions as given by the u.s. Navy. 

DISTRIBUTION OF EARTHQUAKE 

HYPOCENTERS 

The temporal variation of seismicity in the 

western Transverse Ranges for the period 1970-75 

is difficult to assess because the distribution 

of seisrrograph stations changed rapidly. Some 

increase in the nurrber of earthquakes located in 

the later years is undoubtedly reJ.c>tej to an increase in the nurriber of stations. 

The spatial variation of seismicity in the 

western Transverse Ranges can be asse.~sed over 

the period 1970-75 because we have sh~ that 

the location errors are generally not large. 

Table 3.--Griteria for determining Q 

[Q is based on both the station distribution with respect to the earthquake and the statistical 

measures of the solution, and both are rated by independent schemes. Q is taken as the average of 

the ratings from the two schemes: an A and a C yield a B; two B 's yield a B. When ratings are only 

one level apart the lower one is used: an A. and a B yield a B. >, greater than, <, less than] 

Solution quality of hypocenter Station distribution Statistical neasures 

Q 

Epicenter Focal depth NO GAP DMIN RMS ERH ERZ 

------------------------------------------------------------------------------------------------ A-----Excellent---------Good------ > 5 

B----Good--------------Fair------ >5 

C----Fair--------------Poor------ >5 

D----Poor--------------Poor------ <6 

~goo 

.s._ 135 

:S 180 

> 180 

7 

~Dept.~ or 5 km 

~ 2 x Depth or 10 km 

< 50 km 

> 50 km 

< 0.15 s < 1.0 km < 2.0 km 

< 0.30 < 2.5 < 5.0 

< 0.50 < 5.0 > 5.0 

> 0.50 > 5.0 > 5.0 
Plate 1 shows a plot of relocated earthquake 

epicenters in the western Transverse Ranges from 

1970 to 1975. M:>st of the earthquake epicenters 

in plate 1 may be loosely grouped into three 

east-west-trending sets: ( 1) along the southern 

front of the Transverse Ranges, corresponding to 

a canplex fault zone that includes the Santa 

M:mica-Anacapa fault, the ~alibu Coast fault, 

and the Santa Cruz Island fault; (2) along the 

east-central part of the Santa Barbara Channel, 

corresponding to the Pitas Point-Ventur;':l_ fault, 

Oak Fidge fault, and several other east-westtrending faults detected by acoustic profiling; 

and (3) along the Santa Barbara coast and parallel to the coast to the east, corresponding 

to the Red Mountain and San Cayetano faults, 

Arroyo Parida fault, and several unnamed faults 

5 to 10 krn offshore. Significant earthquake 

activity was also detected outside the study 

area south of Santa Rosa Island and seaward to 

Point Arguello. 

Many of the faults in the western Transverse 

Panges that sha.v evidence of Holocene or late 

Quaternary displacement, including rrost of the 

faults in groups (1) and (3) above, are reverse 

faults. Because rrost of these faults are not 

vertical, epicenters of earthquakes associated 

with them do not generally aline with their surface traces. Epicentral distances fran the surface trace depend on focal depths and the dip of 

the fault. Because earthquake hypocenters and 

fault dips are uncertain the relation between 

earthquake epicenters and mapped faults is 

usually not certain. Nevertheless, the approximate association of earthquake epicenters with 

mapped faults is striking. In order to further 

delineate the association, we plotted earthquake 

epicenters using symbols representing their 

A 

A 

-15-

FAULT X 

I 

X 

X 

X 

FAULT Y 

I 

MESA-ARROYO 

PAR IDA FAULT 

I 

X 

X 

X 

focal depths (pl. 2). Focal depths qenerally 

increase north of mapped faults, as .,,.;ould be 

expected from the local geology. 

To further illustrate possible associations 

between earthquake hypocenters and mapped faults 1 

we constructed four cross sections (.A-A' , B-B' 1 

c-c' , and D-D' ) as shown on plate 2. Earthquake 

hypocenters up to 6 krn from line A-A 1 were projected at right angles onto the cross section as 

sha-m in figure 2. To eliminate poorly determined hypocenters, we used only quality A, B, 

and C solutions. 

Two methods were used to test th~ associations between hypocenters and surface. fault 

traces. In the first, we assurred that the 

earthquakes were separate groups to b~ associa ted with the nearest knavn surface fault trace 

and tested the distribution of hypocenters about 

the fault trace using the method of York (1966), 

in which :r and y coordinates are assmr~ to be 

equally subject to error and fitted to a leastsquares line. For section A-A 1 this test indicates that fault X and the ~IJesa-Arroyo Parida 

fault are near-vertical and that fault Y dips 

about 77° north (fig. 2A.). 

In the second method, the appare'1t dips of 

the primary focal planes of the fault-plane solutions were projected onto the section~ parallel 

to structure. For section A-A' , this test suggests that the Pitas Point fault may generate 

much of the seisrnici ty north of its m":1p trace, 

possibly including the Santa Barbara earthquake 

of Aug. 13, 1978 (event SB 78, fig. 2B). 

Cross section B-B 1 extends north -south 

through the Pitas Point and Red .r-buntain faults. 

The data projected on the cross section were 

chosen with the same criteria as for section A-A' . 

From the results (fig. 3) , we deduce that the dip 

B MID-CHANNEL FAULT ZONE 

PITAS POINT MESA-ARROYO 

FAULT X FAULT FAULTY PA~IDA FAULT 

I I I I 

en X l:k:: X w ~ 

I- >0< 

w X 

~ -5 

-J I s;2 

~ X~ v~" ~X '< ~2 X x 

:X::~ X 4~\x ~ X X X 

I-

~ ~'-{18 X X 0.. X X 

w SB X X 0 X ~'loo 'fl 

-~0~~~~~~~1~0--~~~--~~~~~~~--~~30 -~0 10 ~ 30 

Figure 

DISTANCE, IN KILOMETERS DISTANCE, IN KILOMETERS 

2.--cros~-sectional plots of hypocenters along line A-A' (pl. 2). Size of symbol is proportlonal to earthquaJ:e magnitude. A, Distribution of hypocenters tested by using method 

of York (1966). B, Heavy bars represent apparent dip of primary focal plane of numbered 

event as projected parallel to structure. (Hypocenters projected normal to line of 

section.) Numbers refer to plate 2 and table 4. 

8 
B B' 5,-~~--~~-,--~~------~~--~--~~ 

If) 

a::: 

w 

I-§ -5 

~ 

~ 

Ita... 

PITAS POINT 

FAULT 

I 

RED 

MOUNTAIN 

FAULT 

I 

57' 

·" ~65 

·. :~05 . 

""58 

3~<~ 38~ 

\ ~ 

\ 

10 20 30 

~ ~t 0~~~--~~~--~~~--~~~--~~~--

DISTANCE, IN KILOMETERS 

Figure 3.--cross-sectional plot of hypocenters 

along line B-B 1 (pl. 2). Size of symbol is 

proportional to magnitude. Heavy bars represer,t apparent dip of prirrary focal plane of 

numbered event as projected parallel to 

structure. (Hypocenters projected normal to 

line of section.) Numbers refer to plate 2 

and table 4. 

angle for the Red J'vbuntain fault from the hypocenter data is 57°N. 'Ihis is in excellent agreement with a dip of 60°N based on well data (R. S. 

Yeats, written ccmnun., 1978) . The projected 

apparent dips of primary focal planes also indicate that sane of the seismicity in this area may 

be associated with the Pitas Point fault. 

Cross sections c-c 1 and D-D 1 are constructed 

perpendicular to the Anacapa fault in the Point 

Mugu area (pl. 2). Earthquake hypocenters (solution quality A and B only) up to 3 krn from line 

c-c 1 were projected onto the cross section (fig. 

4). We deduce that the Anacapa fault dips 48°N, 

in excellent agreement with a dip of 44°N obtained 

from the fault-plane solution for the magnitude-6 

Point Mugu earthquake. Cross section D-D 1 extends 

through the Point Mugu aftershock area. Earthquake hypocenters (solution quality A and B only) 

up to 3 krn fran line D-D' were projected onto the 

cross section (fig. 5). 'Ihe hypocenters in cross 

section D-D 1 may be separated into two groups 

associated respectively with the Anacapa fault and 

fault z. Fran the hypocenter data, we deduce that 

the Anacapa fault dips 45°N, in excellent agreement with the result from cross section c-c' and 

al.rrost identical to the dip of 44 °N deduced from 

the fault-plane solution of the Point Mugu main 

shock. 'Ihe dip for fault Z is 41 °N, which is very 

close to that for the Anacapa fault. 

EARTHQUAKE FOCAL MECHANISMS 

The HYP071 canputer program plots the P-wave 

first notions of an earthquake in an equal-area 

projection of the looer focal hemisphere 0 The 

9 

5 

0 

t/) 

0:: 

w 

1-

w 

~ -5- 0 

== 

~ 

z 

I, -10-

1-

c... 

w 

0 

-15 

c 

ANACAPA 

FAULT 

I 

"'48° 

"'"" ~ / 

~ "' 

Pom• Mugu 

ma1r ~hack 

x(Nax 197) 

>X 

DISTANCE, IN KILOMETER!: 

Figure 4 .--cross-sectional plot of hy-r:-xenters 

along line C-·C 1 (pl. 2) . Size of ~ymbol is 

proportional to earthquake magni tuce 0 Heavy 

bar represents apparent dip of prim-rry focal 

plane of numbered event as projected parallel 

to structure. (Hypocenters projected normal 

to line of section.) Number refers to plate 2 

and table 4. 

position of a first-rrotion reading in the focal 

hemisphere plot is determined by (1) the azimuthal 

angle between the earthquake epicenter and the 

station, and (2) the emergence angle of the 

seismic ray fran the earthquake focus to the sta-

(/) 

a::: 

w 

1--

w 

~ -5 

= ~ 

~ 

I, -10 

1--

a... 

w 

0 

0 10 20 

DISTANCE, IN KILOMETERS 

Figure 5.--cross-sectional plot of hyt~enters 

along line D-D 1 (pl. 2). Size of symbol is 

proportional to earthquake magnitude. 
ti:>n. If there are enough accurate first-rrotion 

readings fran a well-located earthquake (at least 

six), it is generally a simple task to derive the 

fault-plane solution manually fran the firstrrotion plot generated by the HYP071 program. 

In practice, there are difficulties and carrr 

plications. First, the polarity of a seismograph 

station may have been reversed so that the firstnotion reading from the seismogram is opposite to 

reality. Second, the distribution of seisrnograph 

stations is variable with respect to a given 

earthquake. Third, the first rrotion of a P-wave 

at noisy or distant stations may be difficult to 

identify. Fourth, it is difficult to locate an 

earthquake accurately without a dense network of 

stations and calibrated explosions. Therefore, 

great care must be taken in order to obtain an 

accurate earthquake focal mechanism. We illustrate these difficulties with an example. 

Lee and Vedder (1973) published a fault-plane 

solution constructed fran c::orrposite first rrotions 

of ten small earthquakes in the Santa Barbara 

Channel (fig. 6). They inferred a left-lateral 

strike-slip notion on a north-dipping, east-westtrending fault. However, their solution is unique 

only if the two first-rrotion readings at station 

PYR are accurate. Our re-examination suggests 

that this is probably not the case-the P-arrivals 

at PYR are emergent and not clearly defined for 

these earthquakes and it is difficult to correctly 

identify the first rrotion. If we reverse or 

ignore these two questionable readings , an entirely different fault-plane solution is obtained, as 

shown in figure 6B. 

In the present study, we took several steps 

to reduce the chance of errors in fault-plane 

solutions. First, we systanatically determined 

the polarity of USGS stations using large teleseisms or nuclear explosions (see Houck and 

others, 1976 for details) . Second, we rejected 

fault-plane solutions derived fran data of marginal quality or quantity. Third, we carefully 

re-examined the first-rrotion readings of pranising fault-plane solutions before we accepted th~ 

As a result, we obtained 49 acceptable solutions 

from several hundred first-rrotion plots (table 4). 

These fault-plane solutions are shown in plate 2, 

and individual solutions are shown in figure 7. 

We note that most fault-plane solutions show reverse faulting along east-trending faults which 

may dip either north or south. We chose the 

north-dipping fault planes because they best fit 

the local geology and the distribution of earthquake hypocenters. A detailed discussion of the 

earthquake focal mechanisms and their tectonic 

implications is given in Chapter B of this report. 

DISCUSSION 

The primary finding of this study is that 

independent seismological evidence fully supports 

geologic evidence that much of the western Transverse Ranges is daninated by north-dipping reverse faults that fonn extensive east-trendlng 

zones, especially the Anacapa-Santa M)nica, MidN 

A 

N 

EXPLANATION 

o Dilatction 

• Compession 

I Slip vector 

...::..__ Arrows indicate 

---"7 relati·te movement along fault 

Figure 6.--Fault-plane solutions based on composite 

first notions of 10 earthquakes in Santa Barbara O."'iannel, fran Lee and Vedder (1973). A, 

Solution includes readings at station PYR. B, 

Alternative fault-plane solution excludes readings from two distant stations (PYR arrl SBCC). 

Channel, Pitas Point-Ventura, and Red M)untainSan Cayetano faults. The georretry arrl characteristics of these faults have been deduced fran 

both the spatial distribution of earthquake hypocenters and fault-plane solutions of wellreoorded earthquakes, as well as surface and sul:r 

surface geologic data. Our work derronstrates 

that detailed studies of earthquakes from a 

sufficient nmnber of local seisrnographic stations 

10 
Table 4 .-Data on. mapped focal mechanisms 

Time (GCI') Focal planes Slip 

Event Map Depth Primary - Auxiliary P-axis Vector 

no. coord Yr Mo Dy Hr:Mn:Sc (krn) Mag Azi Dip Azi Dip Azi Pl Azi Pl 

8 C2 70-02-20 7:35:35 12.3 2.4 116 35N 116 55S 26 0 26 35 

21 D2 70-04-16 21:55:48 8.9 2.9 108 76N 50 24S 0 30 304 48 

30 D3 70-05-25 2:57:54 8.0 2. 7 156 44E 170 46W 72 2 80 44 

35 B4 70-06-20 15:27:31 8.0 3. 1 146 60E 146 30W 56 0 56 60 

40 F2 70-08-26 1: 8:59 8.0 3.6 112 6UN 160 40S 42 12 70 60 

41 02 70-08-29 8:14:16 8.0 2.3 118 50N 164 sow 50 0 72 40 

51 C2 70-12-06 1:19:33 15.5 2.0 98 60N 144 40W 26 13 54 50 

64 H2 71-02-16 4:3 7: 3 5.4 3.6 96 50N 80 44S 0 0 10 48 

74 H3 71-04-02 5:40:24 3.4 3.8 100 42N 78 52S 178 3 347 39 

90 D2 71-05-07 2: 3:21 10.4 2.6 118 50N 118 40S 28 5 26 50 

100 C2 71-05-15 16:54:13 13. 7 2.7 90 35N 138 60W 214 15 46 24 

129 F2 71-11-04 19:17:39 11. 1 2.5 177 56S 177 34N 176 11 176 56 

144 A2 72-01-17 5:49:58 10.3 2.7 116 76N 116 14S 26 21 10 75 

158 D2 72-04-04 5: 2:56 8. 7 3. 1 108 44N 86 48S 186 5 356 42 

162 C2 72-04-17 0:28:38 8.9 3.0 95 57N 42 46S 340 6 312 44 

165 H4 72-06-11 11: 5: 4 10.9 2.8 134 84N 52 36S 21 25 330 53 

166 C2 72-06-15 16:42: 9 13.4 2.2 130 65N 13 45W 68 12 102 45 

172 G3 72-07-14 23: 1: 15 6.6 2.7 107 70N 134 25S 21 21 46 67 

173 Gl 72-07-27 1: 12: 4 8.0 3.0 90 85N 24 lOE 346 45 292 79 

197 F3 73-02-21 14:45:57 12.2 5.9 86 44N 86 46S 356 0 347 44 

288 H4 73-03-26 1:27:44 8.0 2.5 100 28N 144 70W 220 23 54 20 

297 C2 73-03-29 17:54:16 14.2 3.3 108 45N 136 sow 213 4 32 40 

357 E4 73-08-06 23:29:16 13.8 5.0 115 50E 130 50S 211 5 44 48 

359 E4 73-08-06 23:53:46 13.7 1.9 150 62E 130 30S 53 15 40 60 

365 E2 73-08-15 2:16:21 4.3 3.0 112 40N 112 50S 202 5 22 40 

371 F4 73-08-20 14: 1:49 8.0 2.5 104 60N 87 30S 8 15 3 60 

376 F2 73-08-24 9: 4:55 13.4 2.4 120 50N 158 50S 228 2 70 44 

385 H3 73-09-02 6: 2 8: 3 13.9 2.3 46 44N 91 56S 162 6 1 34 

388 E2 73-09-04 9:11:25 11.5 3.4 103 52N 72 42S 358 6 340 48 

391 E2 73-09-07 15:18:10 9. 9 2.6 98 40N 98 50S 189 5 8 40 

396 F2 73-09-13 13: 7:45 12. 1 2.2 146 48E 136 40W 52 6 47 47 

397 F2 73-09-13 13: 8:37 16.0 2.2 142 50E 148 40W 54 5 12 42 

418 H2 73-11-14 17:15:31 13. 1 2.2 142 60E 142 30W 52 0 52 60 

426 G3 73-12-20 14:23:21 13.3 2.1 152 50E 6 44W 78 5 96 44 

428 H2 73-12-25 6: 9: 3 11. 3 2. 1 120 58N 162 36W 48 14 78 48 

449 D2 74-02-27 12:25:36 8.0 2.3 114 52N 70 48S 2 2 340 42 

450 H2 74-03-03 16: 2 9: 1 12.9 2.2 158 32E 154 66W 66 12 54 32 

472 F3 74-04-25 8:23:53 8.9 2.8 91 72N 118 208 6 27 28 70 

482 03 74-07-09 0:5~:49 10.8 2.0 122 60N 122 30S 32 15 34 60 

505 E2 74-09-23 2:22:59 6.5 2.0 128 54N 128 36S 3b 9 36 54 

553 G4 75-01-11 14:44:18 13.0 2.5 85 45N 85 45S 6 0 6 45 

555 H4 75-01-23 3:48:42 8.0 2.8 114 90N 24 90E 339 0 114 0 

557 H3 75-01-28 5:22:22 8.0 2.4 52 50N 96 50S 344 0 6 40 

558 D2 75-01-28 9:45:49 8.0 2.5 137 54E 108 40S 33 7 18 50 

570 H3 75-03-01 5:45: 4 6.6 2.0 128 56N 72 52S 11 3 342 38 

575 Gl 75-03-24 10:32:25 12.2 2. 7 98 60N 118 32S 15 15 28 58 

576 G2 75-04-10 21:19:26 6. 7 2.0 90 44N 126 52S 200 4 34 40 

618 1)2 75-10-09 6:16:56 11.8 2.6 77 50N 96 42S 356 6 8 48 

625 H4 75-11-03 3:42:17 16.6 1.8 132 84N 45 54S 20 35 314 35 

SB 78 02 78-08-13 22:54:52 1-2. 5 5. 1 114 40N 158 60S 229 10 68 30 

11 
21 

N 

40 

51 

I 

I 

Jc------~ I c 

\ + 

\ 

162 

297 

I 

D 

\ 

\ 

'\ 

;>, ........ -....... .-.....__ --

N 

+ 

c +/ 

-----_..,.,,.,.... 

\ 

\ 

\, c 

" ' 

+ 

............... c 

/ 

-----

D 

I 

/ 

/ 

D 

I 

I 

41 

129 

166 

N 

I 

/~ t>. 

I \ 

o, ' c 

~ \ 

\ 

\ 

\. 

N 

Figure 7.--First-motion data and focal mechanisms for selected events from 1970 through 1975 for 

western Transverse Ranges. Numbers keyed to plate 4, and table 1. C, compre:cosion; D, 

dilatation; B, two compressions; E, two dilatations; +, weak compression; -, weak 

diJatation; T, tension axis; P, pressure axis; ~, slip vector; solid arc, primary focal 

plane; dashed arc, auxiliary plane. Equal-area projection of lower focal hemisphere. 

12 
N 

N 

N 

N 428 

I 

I 

I 

c/~o 

c I ~ 

~ I + ~ c 

I 

~ \ 

\ ', ' ............ ..... c _ 

N 505 

T 

I 

I 

I 

\ 

\ 

\ 

\ 

' ' 

+ 

'-.... ........... 

Fi~e ?.--continued. 

13 

N 
N N N 

I 

I 

4--D-c 

lc c ~ o{ ~". <t, I E' t:. 

\ B -

I + D 

' \ 

\ 

\ D 

\ + 

', D 

', D o·, ......... 

Figure 7.--continued. 

can help delineate active faults in three dimensions and aid in the interpretation of local 

geology and tectonic features. 

Our locations for the Point Mugu earthquake 

and its aftershocks differ slightly from those 

given by Stierrnan and Ellsworth (1976) • For example, we located the main shock about 2 krn 

south of that given by Stierman and Ellsworth 

and about 5 krn shallower. These differences result because (1) we used more arrival t~s, 

and (2) we used a different crustal velocity 

model and station delays. By studying a small 

area in greater detail, Stiernan and Ellsworth 

(1976) have constructed a far more realistic 

crustal model for the Point Mugu area; our 

rrodel was deduced for the whole western Transverse Ranges. Nevertheless, it is interesting 

to note that the difference in epicenter location is generally within one standard error 

given by these two sets of solutions, whereas 

the difference in focal depth is generally 

within two standard errors. 

REFERENCES CITED 

Allen, C. R., St. Amand, Pierre, Richter, C. F., 

and Nordquist, J. M., 1965, Relationship 

between seismicity and geologic structure 

in the southern california region: Seismological Society of America Bulletin, v. 55, 

p. 753-797. 

Allen, C. R., Engen, G. R., Hanks, T. C., 

Nordquist, J. M., and Thatcher, W. R., 

1971, Main shock and larger aftershocks of 

the San Fernando earthquake, February 9 

through March 1, 1971: U.S. Geological 

Survey Professional Paper 733, p. 17-20. 

Allen, C. R., Hanks, T. C., and Whitcomb, J. H., 

1973, San Fernando earthquake: Seismological studies and their tectonic implications, 

in Murphy, L. M. , ed. , San Fernando, California, earthquake of February 9, 19 71 : 

National Oceanic and Atmospheric Administration, U.S. Department of Conmerce, v. 3, 

p. 13-21. 

Boore, D. f1., and Stierrnan, D. J., 1976, Source 

parameters of the Point Mugu, California, 

earthquake of February 21, 1973: Seismo14 

logical Society of America Bulle. tin, v. 66, 

p. 385-404. 

Castle, R. 0., Church, J. P., Elliott, M. R., and 

Savage, J. c., 1977, Preseisrnic and coseismic 

elevation changes in the epioentral region 

of the Point Mugu earthquake of February 21, 

19 7 3 : Seismological Society of America 

Bulletin, v. 67, p. 219-231. 

Eaton, J.P., 1969, Hypolayer--a COIT!fUter program for detennining hypocenters of local 

earthquakes in an earth consisting of uni .... 

form flat layers over a half-spa~e: U.S. 

Geological Survey open-file report, 155 p. 

Ellsworth, W. L., Campbell, R. H., Hill, D. P., 

Page, R. A., Alew-ine, R. W., III, Hanks, 

T. C., Heaton, T. H., Hileman, J. A., 

Kanamori, Hiroo, Minster, Bernard, and 

Whitcanb, J. H., 1973, Point Mugu, califor.,.. 

nia, earthquake of 21 February, 1973, and 

its aftershocks: Science, v. 182, p. 1127-

1129. 

Friedman, M. E., \-Vhitcornb, J. H., Allen, C. R., 

and Hileman, J. A., 1976, Seismicity of the 

southern california region, 1 January 1972 

to Decerrber 1974: Pasadena, calif., Seismology Laboratory, California Institute of 

Technology, 92 p. 

Fuis, G. S., Friedman, M. E., and Hileman, J. A., 

1977, Preliminary catalog of earthquakes in 

southern California, July 1974 to September 

1976: U.S. C".,eological Survey Open-File 

Report 77-181, 107 p. 

Geiger, L. , 1912, Probability method for the 

detennination of earthquake epic~nters from 

the arrival time only (translate. ':I fran 

Geiger's 1910 German article): Bulletin of 

St. Louis University, v. 8, p. 5~-71. 

Hamilton, R. M., Yerkes, R. F., Brown, R. D., Jr., 

Burford, R. 0., and DeNoyer, J. M. , 1969, 

Seismicity and associated effects, Santa 

Barbara region, part D of Geol0<]' 7 , petroleum 

developnent, and seismicity of the Santa 

Barbara Channel region, california: U.S. 

Geological Survey Professional Paper 679, 

p. 47-68. 

Healy, J. H., 1963, Crustal structure. along the 

coast of California from seismic refraction 

measurements: Journal of Geophysical Research, v. 68, p. 5777-5787. 
Hileman, J. A., Allen, C. R., and Nordquist, J. 

M., 1973, Seismicity of the southern California region: Pasadena, California Institute of Technology, Division of Geological and Planetary Sciences, Contribution 

no. 2385, 487 p. 

Houck, S. T. , Guerrero, J. D. , Miller, A. E. , 

and Lee, w. H. K., 1976, Handbook for 

U.S.G.S. central California Microearthquake 

Nebx:>rk 1969-1975: u.s. Geological Smvey 

Open-File Report 76-2821 249 p. 

Kirkman, S. L. 1 and Ellsworth, W. L. 1 1977al 

Catalog of earthquakes in the Santa Barbara 

Charmel area, Januacy 1972-December 1973: 

u.s. Geological Survey Open-File Report 

77-3021 21 p. 

Kirkman, S. L., and Ellsworth, W. L., 1977b, 

Catalog of earthquakes in the Santa M:mica 

:r.Duntains area, February 21-December 31, 

1973: U.S. Geological Survey Open-File 

Report 77-301, 23 p. 

Lee, W. H. K., Bennett, R. E., and Meagher, K. L., 

1972, A method of estimating magnitude of 

local earthquakes fran signal duration: 

U.S. Geological Survey open-file report, 

28 p. 

Lee, W. H. K., Eaton, M. S., and Brabb, E. E., 

1971, The earthquake sequence near Danville, 

California, 1970: Seisrrological Society of 

America Bulletin, v. 61, p. 1771-1794. 

Lee, W. H. K., and Lahr, J. C., 1975, HYP071 

(Revised) : A ccmputer program for determining hypocenter 1 ma.gni tude, and first 

notion pattern of local earthquakes: u.S. 

Geological Survey Open-File Report 75-311, 

114 p. 

Lee, l·v. H. K., and Vedder, J. G., 1973, Recent 

earthquake activity in the Santa Barbara 

Channel region: Seisrrological Society of 

America Bulletin, v. 63, no. 5, p. 1757-

1773. 

Richter, C. F. , 19 58, Elerrentary seisrrology: 

San Francisoo, W. H. Freeman and Canpany, 

768 p. 

Shor, G. G., and Raitt, R. W., 1958, Seismic 

studies in the southern California continental borderland: International Geological 

15 

Congress, 20th Session, Proceedin~·s, v. 9 , 

p. 243-259. 

Stsvart, G. S., 1973, Prediction of the Pt. Mugu 

earthquake by two methods: Stanfc-.:-d, Calif. , 

Stanford University Publications jn the 

Geological Sciences, v. 13, p. 477-478. 

Stierman, D. J., and Ellsworth, W. L., 1976, 

Aftershocks of the February 21, 1S'73 Point 

Mugu, California earthquake: SeiEm::>logical 

Society of America Bulletin, v. 6f, no. 6, 

p. 1931-1952. 

Sylvester, A. G., Smith, s. w., and Scrolz, c. 

H., 1970, Earthquake swarm in the Santa 

Barbara Channel, California, 1968: Seisrrological Society of America Bulletin, v. 60, 

p. 1047-1060. 

Townley, s. D., and Allen, M. W., 1939, Descriptive catalogue of earthquakes of the 

Pacific Coast of the United State~, 1769 to 

1928: Seisrrological Society of America 

Bulletin, v. 29, no. 1, p. 1-297. 

TUcker, B. E., and Brune, J. N., 1973, Seisrrograms, S-wave spectra and source parameters 

for aftershocks of the San Fernaneo earthquake: Seisrrological studies and their 

tectonic implication, in Murphy, L. M., ed., 

san Fernando, california earthqua}··'?. of 

February 9, 1971: National Oceanic and 

Atmospheric .Administration, U.S . Department 

of Commerce, v. 3, p. 69-121. 

U.s. Geological Survey, 1969, Geology, petroleum 

developrent, and seismicity of the Santa 

Barbara Channel region, California: U.S. 

Geological Survey Professional Paper 679, 

77 p. 

u.s. Geological Survey, 1975, Draft environmental 

statement; Oil and gas develop:nent in the 

Santa Barbara Channel outer oontinental 

shelf off California: u.s. Geological Survey, 3 volumes. 

Whitcomb, J. H., Allen, C. R., Garmany, J. D., 

and Hileman, J. A. , 1973, San Fernando 

earthquake series, 1971: Focal mechanisms 

and tectonics: Revi~ of Geophysics and 

Space Physics, v. 11, no. 3, p. 693-730. 

York, D., 1966, Least-squares fitting of a 

straight line: Canadian Journal of Physics, 

v. 44, p. 1079-1086. 
Table 2.--List of earthquakes in the western Transverse Ranges~ 7,9?0-?5 

[The following data are given for each event: 

Origin time in Greenwich Civil Time: seoonc: through seventh oolumns. 

Epicenter in degrees and minutes of north latitude (LAT N) arn west longitude (IDNG W). 

DEP'lli, depth of focus in kilaneters . 

MAG, Richter rnagni tude of the earthquake. 

NO, nunber of stations used in locating earthquake. 

GAP, largest azimuthal separation in degrees between stations. 

I:f.ITN, epicentral distance in kiloneters to the nearest station. 1 

1M3, root-mean-square error of the time residuals: RMS = [~. (R .2/No) ]'2 where R. is the ob~erved seismicwave arrival tine minus the oorrputed time at the ith station:- 1, 1 1, 

ERH, standard error of the epicenter in kilom=ters: ERH = [SDX2 -SDY2 ]'2. SDX and SDY are the standard 

errors in latitude and longitude, respectively, of the epicenter. ltolhen NO <5 1 ERH cannot be carputed 

and is left blank. 

ERZ , standard error of the focal depth in kilaneters. When NO < 5, ERZ cannot be canputed end is left 

blank. If ERZ ~ 20 krn, it is also left blank. 

Q, solution qualIty of the hypocenter. This measure is intended to indicate the general reliability of 

each solution. See table 3 for criteria that determine Q] 

EVENT lEAR MON DY HF !iN SEC LAT N LONG W DEPTH "AG NO GAP DMIN RPIS ERH ERZ Q 

1 1970 JAN 2 10 45 21.5 34-11).9 119-41.5 9.4 3.4 10 152 19.8 o. 16 1. 3 1. 2 c 

2 2 19 57 47.5 34-17.7 119-42.9 3.8 2.6 8 229 16.3 o. 22 2. 9 4.3 D 

3 & 5 17 42.9 34-29.3 119-18.6 8.0 2.3 1 191 37.0 0.25 9.5 6.3 D 

4 10 2 47 2.9 34-2 5. 7 119- 8. 6 12.6 3.0 16 140 40. 1 o. 27 1.6 1. 1 c 

5 14 17 17 4.7 JIJ-23.0 119-52.2 4.2 2.0 7 180 18.8 0.10 0.8 14. 1 D 

6 29 15 32 59.4 34-2 5.2 11q-!)5.4 13.9 1. 9 6 156 12.8 o. 13 1. 5 1. 4 c 

7 f'EB 14 12 56 24.7 34-14.5 119-40.7 8.0 2.4 7 79 27.7 0.19 -1.5 3. 1 c 

8 20 7 35 35.2 34-23.4 119-46.0 12.3 2.4 8 118 7.6 0.08 0.7 0.6 B 

q MAR 4 17 24 57.3 34-22.6 120- 8.2 11.2 1. 9 6 121 31.8 o. 25 2.1 13.6 c 

10 7 16 48 50.5 33-56.5 118-49.5 5. 3 2.7 9 201 28.9 0.23 2.4 2.5 c 

11 13 20 40 9.7 34-24.3 119-34.0 12. 7 1. 8 6 140 17.0 0.07 0.8 0.9 B 

12 20 12 48 43.8 34-21.11 120-24.1 8.0 1. 9 6 188 22~7 0.26 4.0 D 

n 20 13 18 36.6 34-21.3 120-25.4 8.0 2.0 6 196 22.9 0.21 3. 3 17.5 D 

14 23 13 16 9.4 34- 2.5 119- 6. 7 7. 9 1. 9 7 182 8.7 0.18 1. 9 2.0 c 

15 26 22 0 20.8 34-1 5.9 119-37.6 8.0 2.7 12 86 21. 2 0.29 1. 9 2.6 c 

16 29 13 11 6.3 34- 3.5 118-59.2 8.0 1. 9 5 241 9.0 0.03 0.6 0.7 c 

17 29 16 7 17.8 34-15.6 119-38.0 11. 3 1. 8 6 124 27.2 0.05 1.4 0.8 c 

18 J1 11 1 51. 5 34-15.B 119-34.7 4.5 2.8 12 80 .23. 3 0.20 1. 0 2. 1 c 

19 APJ. 6 2.3 3 50.6 34-22.6 119-37.0 8.0 2. 1 6 154 11.3 0.12 2.0 5.3 c 

20 15 23 32 4.0 34-22.~ 120-24.1 8.0 1. 9 6 1R8 20.8 0.26 2.9 11.2 D 

21 16 21 115 48.5 34-15.7 119-42.2 8.9 2.9 13 76 19. 9 0.17 0.9 1. 1 c 

22 19 7 11 58.8 34-28.6 119-49.3 3.2 2.1 6 113 10. 1 0.12 0.4 6.8 c 

23 20 7 31 47.4 34-24.7 118-32.7 2.0 2.7 1 112 34.2 o. 24 1. 5 15. 4 c 

24 22 2 43 29.8 34-31.4 119-25.3 4.3 2. 1 7 142 26.9 o. 27 1. 7 12.8 c 

25 .23 10 42 53.3 34-26.5 119-24.4 8.0 2. 5 8 131 28.2 o. 16 1. 4 1. 6 c 

26 30 3 59 'i2.8 34-14.2 119-33.9 6.q 2. 7 10 90 26.5 0.15 o. 9 1. J B 

27 MAl 2 1 52 3. 3 34-15.4 119-33.4 6.4 2. 3 7 94 29. 9· o. 11 1. 0 1. 9 B 

28 2 15 43 39.3 34-21.2 120-25.4 A.O 2.2 6 196 23.0 o. 26 4.3 D 

29 16 1 47 24.5 34-27.0 119-47.2 11.4 3.3 17 60 6.7 0.27 1. 2 0.9 B 

30 25 2 57 54.4 34-14.7 119-44.5 8.0 2.1 11 87 21.9 0.11 0.7 0.9 B 

)1 25 9 12 52.6 34-14.3 119-46.0 1. 7 1. 9 8 146 23.2 o. 13 1. 1 1.0 c 

32 JUN 11 1 13 o. 1 34-20.2 120- 2.8 3.0 2.7 6 151 22. 1 o. 18 1. 8 15.5 c 

]) 20 14 2 29.4 34-41.7 119-30.1 8.0 2. 1 8 167 29.3 0.29 2.0 4. 8 c 

]4 20 15 23 16. J 33-45.0 120- 4.8 a. 3 2.5 6 185 40.5 0.04 0.5 o. 6 c 

35 20 15 27 31.2 33-45.8 120- 4.2 8.0 3. 1 8 182 39.9 0.18 1. 6 2.0 c 

36 JUL 1 20 0 41.2 34- 2.2 118-51.0 0.5 1. 8 6 205 21.3 0.06 0.7 6.6 D 

37 4 10 9 35. 1 34-42.6 119-31.3 5.9 2.4 q 96 29.5 o. 16 1. 1 1. 8 c ~8 24 11 55 27.1 34- 0.9 119- 8.4 4.9 2.5 9 168 12.6 0.10 0.6 1. 0 B 

39 29 21 13 18. 1 34-35.3 119-'50.0 5.2 2.4 12 84 14.9 o. 34 1. 9 3.4 c 

40 A a.; 26 1 8 59.6 34-19.2 119-14. 1 8.0 3.6 13 75 15.5 0.27 1. 3 1. 6 B 

16 
Table 2.--List of earthquakes in the western Transverse Ranges, l9?0-?5--continued 

EVENT YEAH MOd )Y HR MN SEC LAT M LONG w DEPTH PIAG NO GAP DfUN RMS ERH ERZ Q 

41 19 70 AUG 29 8 14 16.9 34-15.1 119-42.1 8.0 2.3 8 107 21.0 0.19 1.4 2.8 c 

42 SEl? 7 9 35 56.4 34-30.6 119-44.8 1. 6 2.6 8 125 3.3 0.07 0.6 o. 3 8 

43 12 19 17 32.4 34-26.9 119-25.9 7. 0 3. 2 10 185 7. 6 o. 15 1. 8 1. 5 c 

44 12 20 52 14.0 34-15.4 119-38.5 4.9 1. 4 6 123 27.5 o. 14 1. 5 c 

45 OCT 6 8 0 46.9 34-16.6 119-42.5 12.3 1. 6 7 129 24.4 0.11 0.7 0.8 8 

46 17 20 17 5.7 14-34.6 119-49.6 3.9 2.5 10 158 13.8 0.12 1. 1 1. 6 c 

47 NOV 7 15 54 31.2 34-2 5.6 119-27.3 6.3 2.4 6 148 25.0 o. 24 2.~ 1 5. 5 c 

48 8 8 27 8.9 33-52.0 120-16.8 8.0 2.4 7 207 19.9 0.15 1 (\. 0 13.7 D 

49 15 5 10 5.0 34-26.4 119-40.0 23.5 1.9 4 185 7.5 o. 01 c 

50 22 12 0 31.8 34- 7.9 119- 2.0 12.6 1. 9 5 199 3. 8 0.02 r:.1 0.8 c 

51 DEC 6 1 19 33. 2 34-20.8 119-51.4 15. 5 2.0 6 215 16.9 o. 12 (' .. 8 2. 0 D 

52 9 13 3 56.1 34-24.2 119- 8.6 6.9 2.7 1 106 20.0 0.09 (' .. 9 1. 3 8 

53 18 15 29 42.4 33-52.1 118-39.4 2.3 3. 1 9 145 46. 1 o. 21 1. 6 10.7 c 

S!t 30 'J 50 6.5 34-17.4 119-46. 1 1. 6 2.0 8 135 17.6 o. 18 1.4 1.8 c 

55 31 23 5 11. 4 H-42. 7 120-17. 3 8.0 J.O 8 121 19.7 o. 21 1. 5 2.a c 

':6 1 y /1 JA:-1 1 20 36 20.2 34-19.4 119-17.9 3. 7 3. 1 8 168 11.5 o. 31 :'. 5 8.9 c 

')7 8 9 31 2. 1 )q- 1. 1 119-41.9 20.0 1. q 1 1a4 6. 6 0.13 1. 4 1. 3 8 

58 !:i 10 15 41.0 34- 1.9 119-40.4 19.4 1. 4 7 133 5. 5 0.25 2.3 3.6 8 

59 FEil 1 17 9 50.5 34-14.9 119- 8.a 5. 6 2.5 6 119 16.6 0.08 r.s 0.9 8 

60 5 1 36 46.8 34-28.1 119-26.9 5.0 2. 1 5 138 24.6 o. 21 t4. 4 D 

til 11 4 7 15.5 34-14.7 1 18-31. 0 1 .. 1 3.3 9 111 33.6 0.20 2. 4 15.3 c 

62 13 t> 44 54.7 J4-19.l 118-32.0 0.7 3.2 10 97 33.3 0.23 1. 1 8.7 c 

63 15 23 33 11. 0 34-17.5 118-33.6 0.8 2.9 6 1]3 34.9 0.22 2.2 c 

64 16 4 37 ).'} 34-14.9 1V1-32.2 s. 4 3. 6 6 144 35.4 0.16 1.8 2. 1 c 

65 20 L3 15 57.0 34-1 5. 3 113-34.1 4.8 3.9 6 14 3 38.2 0.23 2. 6 3.6 c 

ti6 21 2 42 11. 6 34-11.1 118-33.1 8.0 3.8 6 134 35.9 a. 12 1. 2 1. 5 c 

(j1 22 10 l5 54.8 34-17.1 11i3-30.q 0.7 3. 1 7 133 35. 1 a.19 1. 1 8.5 c 

68 MAR 5 14 29 59.!4 33-46.8 120- 3.4 10.8 2.3 5 177 39.4 o. 05 1. 0 1.0 c 

69 16 1 j 22 4 3. 8 34-15.0 119-42.6 0.8 2.2 5 132 27.4 0.09 1. 1 D 

70 17 11 27 28.2 )4-27.3 118- :n. 1 0.7 2.7 6 17 J 21.4 0.18 2. 3 c 

71 20 3 49 15. 1 34-26.6 118-34.4 0.2 2.8 7 11 3 2a.6 0.28 2. 8 c 

72 25 0 40 29.4 34-17.6 119-33.4 6.4 1.9 5 138 22.3 0.09 1. 5 14.3 D 

71 APR 1 21 55 47.3 34-11.8 118-3 2. 7 O.f> 2.9 8 150 35.6 a. 16 o.8 9. 5 c 

74 2 5 40 24.1 34-14.4 11R-32.9 3.4 3.8 q 113 36.2 o. 21 1. 6 1. 9 c 

75 b 9 46 31.0 .l4-23.9 119-4'1.9 7.1 2.7 5 160 61. 3 0.04 1. 1 1. 3 c 

76 6 10 26 31. 0 34-27.0 118-42. a 2.9 2 .. 9 6 145 59.0 o. 13 2.11 2.8 c 

77 6 11) 27 51.8 34-2 6. 2 118-40.6 9.1 3.4 5 150 56.5 0.02 0.6 a.7 c 

7A 6 10 28 16.7 34-33.0 11 tl- 38. 5 B. 0 3.6 4 133 6.2.2 0.20 c 

79 15 11 14 31. 9 34- q.o 11 a-.3 2. 4 a.o 4.2 8 187 34.0 0.22 4.0 1. 6 D 

80 15 18 4 15.9 34- 9.0 118-11. 1 <J.1 3.2 13 166 32.0 o. 27 2.6 1.2 c 

81 18 22 27 38. 1 34-26.6 118-42. 4 8.0 3.8 12 103 111.2 ~.09 0.5 a.s 8 

82 19 13 49 11. 9 34-27.0 118-4 3. 2 5. 1 2.5 10 103 13. 2 0.17 0.9 1.4 c 

83 21 3 12 10. 1 34- 9.8 119- 38. 1 14. 3 1.9 7 122 18.7 o. 13 1. 4 1. 3 8 

84 23 6 43 5. 1 34-27.2 118-43.1 11.7 3.4 10 103 49.8 ~- 16 1. 2 1. 5 c 

85 24 0 24 18.1 34-39.7 120-21.1 6.0 2. 5 ·4 156 11.8 o.oo c 

1=16 MAY 5 1 17 32.3 311-27.1 118-30.0 6.7 2.6 8 159 25.6 o. 07 0.8 0.1 B 

B1 7 1 22 30.2 34-14.9 119-40.6 9.2 3.0 13 11 21.7 o. 27 1.2 1. 6 c 

88 1 1 23 37.6 34-15.8 119-41.2 11.8 2.4 6 109 26.0 0.06 0.5 0.7 8 

89 7 1 52 10.9 34-15.7 119-41. 2 8.o 1. 8 6 77 26. 1 o. 06 0.6 5.9 c 

90 7 2 3 21. 9 34-15.a 119-40.3 1 o. 4 2.6 8 76 27.6 o. 28 1. 8 2.7 c 

91 7 2 16 6. 1 34-16.1 119-41.7 2.8 1. 8 6 127 25.4 0.12 0.9 c 

92 1 4 40 12. 6 34-15.6 119-41. 3 6. 1 1.6 8 110 26.3 o. 10 0.1 5.0 c 

93 7 9 26 16.) 34-15.4 119-42.4 8.0 2.0 7 106 26.7 0.21 1. 6 2.7 c 

94 1 11 6 52.4 34-15.6 119-41.1 5.7 1. 9 6 108 26.3 o. 10 1.0 15.8 c 

95 1 18 ]3 14.4 34-17.6 119-39.5 2.3 2.3 1 77 23. 1 o. 14 1. 0 14.0 c 

96 7 18 36 4 3. 8 34-15.~ 119-41. 5 6 .. 5 2.3 6 109 26.6 0.06 o. 7 8.2 c 

97 10 19 54 24.8 34-27.2 118-42.6 1.3 2. 6 7 104 13. 1 0.08 0.6 0.9 8 

98 12 14 51 24.2 34-19.6 119-21.1 3.6 2.5 7 83 9.5 0.44 1. 5 19. 1 c 

99 15 15 21 58.4 34-15.4 119-41.2 8.0 1. 9 7 102 26.6 0.10 0.1 1. 5 B 

100 15 16 54 13. 9 34-27.4 119-46.3 13.7 2.7 10 B4 5.6 o. 10 0.7 o.s A 

17 
Table 2.--List of earthquakes in the western TPansverse Ranges, l9?0-?5--continued 

EVENT YEAR MON DY HR :iN SEC lAT N LONG i DEPTH MAG NO GAP Dftilf RftS ERH ERZ 0 

101 1971 JUN 2 11 52 0.3 34-11.1 118-30.1 0. J 3.6 11 10 3 33.9 0.16 1. 4 1.1 c 

102 4 2 34 45.9 34-18.8 118- 30. 7 5.8 2. 1 5 140 35.2 0.01 1. 1 1.6 c 

103 10 12 )8 25.7 34-14.1 119-41.3 10.5 2.3 8 79 27.2 0.21 1. ] 2.2 c 

104 18 15 30 30.1 33-53.8 119-39.9 12.6 1. 7 6 115 11. 2 0.05 0.6 0.5 B 

105 22 14 9 51.4 34-24.7 118-32.8 0.2 2.3 1 159 24.9 0.23 2.3 c 

106 JUL 4 2 40 49.8 33-51.7 118-42.2 5.2 2.6 9 157 33. 1 0. 11 1. 0 1. 8 8 

107 10 10 36 16.4 34-, 5. 7 119-41.9 A.O 2. 1 9 76 26.0 0.29 1.7 3.0 c 

108 10 14 52 36.7 34-15.9 119-42.3 8.5 1. 8 1 130 25.6 0.05 0.5 0.5 B 

109 13 13 10 26.9 33-50., 120- 4.0 12.4 2.8 9 169 34.6 0.13 1. 2 1. 1 c 

110 19 1b 31 49.9 33-45.7 120- 7.2 6.6 1. 9 8 190 37.3 o. 29 2. 2 2.3 c 

111 AUG 1 7 34 36. 4 34-16.6 118-31. 7 5. 8 3. 1 9 166 35.9 0.14 1. 6 1. 1 c 

112 12 11 38 24.4 34-15.2 119-38. 2 1 o. 9 2.2 6 112 27.9 o. 14 1. 5 1. 6 c 

113 27 12 45 15. 4 34-38.7 119-55.9 8.0 1. 9 4 163 25.9 0. 0 3 c 

114 30 17 58 36.8 34-30.9 118-55.0 8.0 2.1 6 137 11. J 0.07 0.8 0.9 8 

115 31 7 54 2 3. 4 34- 0.4 120-15.6 1.2 1.9 7 201 9.0 o. 13 1. 6 2.4 c 

116 SEP 13 1 3 3.1 34-15.0 119-112.3 1 o. b 2.8 10 82 27.4 0.16 1. 0 1.3 c 

117 13 1 12 21.2 34-1 5.6 119-41.8 5.8 2.6 11 79 20.3 0.25 1. 3 2. 4 c 

118 17 1 46 29.3 34-33.8 120-23.5 1. 1 2.3 4 140 0.8 0.00 c 

119 17 9 19 5. 1 34-17.5 119-43.6 9.0 2.4 6 94 22.1 0.07 0.1 1. 0 B 

120 18 9 3 24.8 H-17 .3 119-44.3 8.0 2. 1 7 15 8 22.4 0.15 1. 4 9.0 c 

121 .22 0 25 35.0 34-15.9 119-41.3 11. 1 2.2 1 11 25.7 0.14 1. 2 1. 3 c 

122 24 0 JO 41.0 34-23.5 119-54.0 8.0 2. 1 5 95 20.7 o. 14 3.1 D 

123 27 20 59 3.2 Jli-11.7 119-21.2 8.0 3.2 14 108 33.1 0.19 1. 0 1. 1 c 

124 OCT 4 1 53 51. 3 34-18.4 119-45.A 4.0 2.5 7 80 21.6 o. 18 1. 3 c 

125 26 14 24 10.5 33-52.1 119-17.7 8. 0 2.1 9 157 34.0 0.10 0.6 0.9 8 

126 28 16 11 58.6 34-15.5 119-41.2 6.3 2.8 6 111 26.6 o. 19 3. 2 c 

127 29 3 47 9.4 34-15.3 119-39.3 8. 0 2.9 10 79 21.3 o. 24 1. 5 2. 1 c 

128 NOV 4 18 22 37.5 34-27.8 119-27.5 8.0 2.0 5 161 23.8 0.40 0.4 4.8 D 

129 4 19 17 39. 1 34-15.9 119- 3.9 11. 1 2.5 6 180 17. 3 o. 14 2. 1 2. 1 c 

130 16 0 37 8.9 34- 6.1 118-49.9 3.2 2. 1 6 151 21.5 o. 16 2. 1 3. 6 c 

131 23 0 36 57.9 34- 3.8 118-49.6 0.5 2. 1 6 133 22.6 0.18 2. 5 c 

132 DEC 14 21 .21 11.9 34-22.9 119-18.5 5. 5 2.0 9 139 3.6 0.10 0.6 o. 8 8 

133 15 18 47 44.4 14-22.6 119-18.5 b.6 1. 4 1 138 3.4 0.07 0.5 0.9 8 

134 18 0 35 36.2 34- 7.0 118-49.1 3. 4 2. 1 8 112 22.8 o. 16 1. 2 2.4 c 

135 19 2 13 36.3 34-23.1 119-19.2 8.8 2.5 9 121 2.8 o. 14 0.8 0.8 B 

136 20 14 29 31.2 34-18.3 120-16.1 8.0 2.1 7 142 30.6 0.25 2.2 3.7 c 

137 21 8 40 19.5 34-43.9 118-55.4 9.7 2.9 14 169 24.7 0.23 1. 8 1. 5 c 

138 JO 19 17 54. 1 34- 6.1 120- a. 3 8.0 2.2 6 146 20.7 0.24 2.6 3.9 c 

139 30 23 3 41.2 34-16.3 119-41.1 8.3 2.2 7 100 25.2 0.09 0.1 1. 2 B 

140 1972 JA!'I 1J 22 51 55.7 31J- 3.1 118-47.5 6.1 2. 1 7 131 25.9 0.23 2n6 3. 6 c 

141 15 22 1 3 3. 8 34- 6.8 118-49.9 0.5 2. 1 1 109 21.5 o. 19 1.8 19.2 c 

142 16 11 46 57.7 34- 4.4 119-40.9 15.1 1.7 6 113 9.9 0.07 1. 1 0.9 B 

143 17 4 57 12.4 34-18.6 120-16.1 8. 0 1. 9 6 142 30.3 o. 21 2.0 5.6 c 

144 17 5 49 58.2 34-17 .a 120-15.1 10.3 2.7 8 141 29.9 0.32 2 .. 6 J. 3 c 

145 17 8 23 49.8 34-18.7 120-11.5 8.0 2. 1 7 150 29.4 o.oa o. 5 1. 5 B 

146 17 9 10 37.6 34-17.9 120-15.7 8.0 2.6 9 141 29.8 0.29 1 .. 8 3. 4 c 

147 20 23 36 29.8 34- 6.1 118-50.2 1. 8 2.2 8 147 21.0 0.18 1 .. 5 1.3 c 

148 25 17 16 4 7. 1 34-23.1 118-30. 1 5.5 2. 1 5 161 30.0 0.05 0.7 15.0 D 

149 31 .6 40 26.4 34-14.1 119-34.0 14. 2 2.3 7 79 25.3 o. 08 0 .. 7 0.8 B 

150 FEB 10 3 ~J8 51. 8 34-26 .\) 118-36.6 7. 9 1. 3 7 143 17.2 0.05 0.4 0.1 B 

151 13 8 57 45.7 )~J-18.7 120-17.2 2.2 1.1 6 148 29.5 0.06 o .. s 0.5 B 

152 19 0 26 49.4 34-25.7 119- 2E. 5 6.0 2.7 10 126 11.2 0.37 2 .. 2 3.2 c 

153 MAR 2 5 2 0.9 34- 0.8 118-33.A 3. 5 1. 9 7 115 14.4 0.08 1. 0 c 

1'l4 15 11 13 13. 2 34- 0.7 119- 7.0 4. 1 2.1 7 179 11.9 o. 19 2.-2 5. 1 c 

155 15 1 3 33 3. 1 34-26.5 119- 9.1 14. 3 2.3 7 15 3 19.5 0.17 1 .. 5 1. 5 c 

156 18 6 52 43.0 34-17.2 119-10.7 6.7 2.6 9 10 4 11.8 o. 18 1. 2 1. 5 c 

157 19 5 6 21.7 34-15.7 119-42.6 0.6 2.2 5 131 26. 1 0.01 o. 1 D 

158 Al'R 4 5 2 56.6 34-27.5 119-30.3 8. 7 3. 1 15 129 11. a o. 15 0.8 o.a c 

1S9 12 1 J2 44.9 )4-.27 .2 119-16.0 11.8 2.2 8 132 11.8 0.12 1. 0 1. 0 B 

160 14 8 5 3.9 34-23.9 119-49.3 9.9 3. 1 1 3 63 11. 1 0.09 0.4 0.4 8 

18 
Table 2.--List of earthquakes in the western Transverse Ranges 3 l970-75-Continued 

EVENT lEAR MON DY HR MN SEC LAT N LONG W DEPTH MAG NO GAP DMIN BliS RBH EBZ Q 

161 1972 APH 14 18 9 26.8 34-24 .o 119-48.7 8.0 1. 8 6 71 111.0 0.12 1. 4 6.5 c 

162 17 0 28 38.4 34-23.3 119-48.8 8.9 3.0 14 64 11.0 o. 19 0.8 1. 0 B 

163 27 4 45 16. 1 34- 4.2 118-58.9 12.8 3. 1 11 125 8.8 o. 27 1. 9 1. 4 B 

164 JUN 6 12 2 22.3 34-11.8 119-47.4 8.0 1. 7 6 104 26.7 0.23 2.3 4.6 c 

105 11 11 5 4. 5 33-52.4 118-43.3 1 o. 9 2.8 8 115 35.7 0.29 2.5 2.6 c 

166 15 1b 42 9.6 34-25.5 119-52.1 13.4 2.2 6 87 17. 1 0.07 0.7 0.7 B 

167 ld 18 4 13.0 34-34.4 120-29.6 7.8 2. 6 7 192 8.6 0.09 1. 1 0.6 c 

168 1<) 3 21 36. q 34-11.(.} 119-4L&.6 10.4 1. 8 6 97 24.7 o. 16 1. 6 3. 1 c 

169 20 5 8 8.3 33-54.'3 119-34.8 11.9 1. 5 8 215 10.3 o. 11 1. 1 0.9 c 

110 24 1 36 49.5 34-39 .o 118-42.8 2. 3 2.4 7 185 9.4 0. 36 4. 6 4.3 D 

111 .26 21 22 39.3 34-20.3 119-23. 1 2.1 2.2 5 108 5. 1 o. 21 2.1 D 

172 JUL 14 2J 1 15.7 34- 3.0 118-47.8 6.6 2.7 10 74 25.5 o. 23 1. 3 2.5 c 

173 27 1 12 4.4 34-43.2 118-56.9 8.0 3.0 13 169 25.5 o. 31 2.9 2.7 c 

114 27 19 58 43.5 34-24.3 119-30.3 1 o. 8 1. 8 1 121 15.3 0.09 0.8 1. 0 B 

175 AU::; 1 6 52 44.3 34-15.4 119-40.4 5.1 2.4 6 105 26.9 0.12 1. 2 c 

176 4 q 25 14.7 34- 5.5 119- 3.6 14.1 2.2 5 175 2.0 0.03 0.5 0.2 c 

117 4 19 36 9. 8 34- 3.5 119- 8.1 16.5 2. 4 7 152 8.7 0.15 1. 6 1. 0 c 

178 7 10 17 50. 3 34-15.9 119-26.6 10.1 2.7 1 94 14.7 0.15 1. 3 1. 5 B 

179 18 3 37 3. 3 34-42.8 120-16.3 8.0 2. 5 5 165 20.7 o. 14 1. 3 1. 9 c 

180 24 11 41 48.8 34- 5.1 119-14. 1 8.6 2.8 6 175 16.0 0.03 o. 3 0.4 B 

181 SEP 16 14 26 34.2 34-35.5 118-46.4 1. 1 2.7 7 118 4.0 0.10 1.1 0.8 B 

182 NOV 1 15 56 18.9 3il-26.9 119-15.4 6. 5 2.2 7 131 11.9 o. 11 1. 1 1. 5 B 

183 5 11 34 10.7 34-16.3 119-41.6 8.6 2.8 5 126 31.3 0.08 1. 2 1. 9 c 

184 9 22 48 5. 1 34- 3.2 118-47.7 5.1 2.5 11 92 25.6 0.21 1.8 3.6 c 

185 18 19 33 24.9 34-16.8 118-34.1 6.1 1.8 9 96 2. 4 o. 22 1. 4 1. 9 B 

Hi6 23 18 56 48.6 34-25.1 118-32. 1 3. 5 1. 9 6 153 12.9 0.12 0.7 8.9 c 

187 DEC 1 1 42 25.6 34-37.3 118-45.2 5.0 2.2 6 130 6.0 0.33 5. 1 6.7 c 

188 13 7 12 42.4 33-54.7 119-37.0 7.8 2. 3 6 109 9.3 o. 10 1.0 1. 7 B 

189 22 13 6 28.3 34- 0.2 118-32.9 8.0 2.6 8 128 14.3 0.15 1. 4 2. 1 B 

190 1973 JAN 4 20 31 9.2 34-15.0 119-35.3 11. 1 2.8 9 83 26.0 0.21 1. 2 1. 4 c 

191 6 1 44 12.5 34-40.3 118-44. 2 0.2 2.4 6 116 69.2 0.25 3.7 D 

192 1 3 51 39.0 33-52.7 118-40.4 8.0 2.1 10 151 32.4 0.18 1. 4 8.5 c 

1q3 FEB B 9 3 32.5 34-25.7 119-49.3 1.5 2.1 5 130 12.5 0.10 1. 9 1.7 c 

194 8 16 38 15.5 33-58.9 118-42.2 6.6 2.8 16 66 26.8 o. 18 o. 9 1.4 c 

195 14 19 8 33.3 34- 5.4 119- 3.2 14.0 2.2 6 176 2.3 0.11 2.3 1. 1 c 

1CJ6 17 7 48 5.6 33-56.2 119-41.0 13.3 1. 6 5 112 7.9 O.Oil 0.7 o. 4 c 

1(.}7 21 14 45 57.2 34- 4. 7 119- 2.3 12.2 5.9 16 62 4.2 o. 26 1.2 1. 1 B 

1qs 21 14 52 15.5 34- 1.1 118-57.7 8.0 2.9 10 159 13.9 0.19 1. 5 1.6 c 

199 21 14 55 7.9 34- 1.7 118-58.4 8.0 3.4 16 67 12.4 o. 21 0.9 1. 4 B 

200 21 1/.J 56 44.7 34- 1.9 118-58.9 8.0 3.3 12 91 11.6 o. 16 0.9 1.6 B 

201 21 15 7 8.0 34- J.O 118-59.8 11.3 2. 1 9 66 9. 1 o. 22 1. 5 1. 6 B 

202 21 15 10 16.9 34- 2.4 118-59.7 11.5 2.0 8 66 10.0 o. 19 1. 6 2.0 B 

203 21 15 18 6.5 34- 1.8 119- 0.6 10.9 2.9 11 86 47.2 0.14 0.9 1. 2 B 

204 21 15 32 14.9 34- 3.3 118-59.0 11. 1 2.9 8 88 9.7 o. 11 0.9 1.0 A 

205 21 15 48 15.9 34- 5.4 118-59.7 13.0 2. 1 7 144 6.8 0.22 2. 3 1. 8 c 

206 21 15 48 29.7 34- 5.4 119- 0.2 11. 5 2.6 9 BJ 6.0 0.12 0.9 0.8 A 

207 21 15 59 26.9 34- 4.4 119- 2.7 11.0 3.4 11 64 4. 5 o. 15 0.9 1. 1 B 

208 21 16 12 24.6 34- 4.9 118-57.4 12.6 2.2 8 89 10.4 o. 10 0.9 1. 0 1 

209 21 16 18 30.9 34- 3.1 118-57.2 12.6 2.9 10 91 12.1 0.08 0.6 0.5 B 

210 21 17 1 4.6 34- 4.7 118-57.6 11.7 2. 1 6 104 10.2 o. 09 1.3 1. 4 B 

211 21 11 4 32.4 34- 2.6 118-58.2 12.2 2.5 1 97 11.4 0.20 2. 1 2. 2 B 

212 21 18 37 13.6 34- 3.2 118-57.9 14.4 2.6 7 95 11.0 o. 16 1. 4 1. 1 B 

213 21 18 54 9. 1 34- 2.8 118-58.3 12.4 2.6 10 89 10.9 0.10 0.7 0.7 l 

214 21 19 2J 22.6 34- 2.9 118-59.7 14.9 2.3 8 66 9.3 o. 15 1. 3 0.9 B 

215 21 19 28 58.6 34- 5.9 119- 1. 0 15.3 2.7 8 81 4.5 0.09 0.8 0.5 l 

216 21 20 41 38.7 34- 4.4 118-59.2 12.1 2.4 8 91 e. 2 0.08 0.7 0.7 B 

211 21 23 55 2.6 34- 4.5 118-58.2 13.5 3. 1 13 68 9.4 o. 13 o. 7 0.6 1 

218 22 0 14 42.0 34- 4.6 118-58.5 12. 1 3.2 14 68 8.6 0.16 0.8 0.7 B 

219 22 0 50 2.7 34- 5.2 118-58.7 14.9 2.5 12 79 7.9 0.09 0.6 0.3 A 

220 22 1 0 30.9 34- 4.1J 118-59.4 11.9 2.4 12 6'f 8.0 0.15 0.9 0.8 B 

19 
Table 2.--List of earthquakes in the western Transverse Ranges, Z970-7~ntinued 

EVENT YEAR MON !>Y HB. MN SEC LAT N LONG W DEPTH lUG NO GAP Dl'IIN RMS BRH ERZ Q 

221 1973 FEB 22 3 8 46.4 34- 2.0 119- 3.0 1 o. 8 2.4 14 67 8.5 0.20 1. 1 1. 2 B 

222 22 4 16 46.4 34- 2.7 118-59.0 11.4 2 .. 8 14 73 10. 1 o. 17 0.9 0.8 B 

223 22 4 20 43.2 34- 3.4 118-57.5 14.1 2.6 11 12 1.1 o. 14 0.9 0.6 A 

224 22 4 40 3.5 34- 3.2 119- o. 1 13.6 2.2 9 86 8. 4 0.07 o.s 0.4 A 

225 22 5 29 6.3 34- 2.1 118-59.2 11.6 2 .. 5 13 11 10.8 o. 20 1. 2 1. 1 B 

226 22 6 29 24. 1 34- 3.1 118-59. 1 11.0 2.5 13 69 9.6 0 .. 20 1. 3 1. 2 8 

221 22 6 33 23.6 34- 1 ·" 119- 1.6 11.4 2. 2 9 85 1 o. 1 0.23 1. 6 1.7 B 

228 22 1 21 39.R 34- 3.5 118-59.4 12.9 2.4 13 65 8.9 o. 20 1. 2 1. 0 8 

229 22 9 30 15.8 34- 5.0 119- 1. 9 14.4 3.7 20 69 o. 5 0.08 0.4 0.2 A 

230 22 9 47 31. 1 34- 4.2 118-58.5 12 .. 9 2 .. 3 14 64 4 .. 2 o. 09 o. 5 o. 3 A 

231 22 10 6 41.0 34- 3.5 118-58.2 13.8 2.3 11 65 3.5 0.13 0.8 0.5 A 

232 22 11 22 52.8 34- 2.2 118-59.7 12.0 2.0 8 124 6.2 0.09 0.9 0.6 8 

233 22 11 56 27.9 34- 1 .B 119- o.o 12.3 2.5 16 11 7.0 o. 19 1. 1 0.8 8 

234 22 13 35 59.6 33-59 .o 118-57.4 3.2 2. 1 6 124 8.4 0.18 ('.5 6.8 c 

235 22 15 22 47.3 34- 4.2 119- 0.3 11.9 2.8 12 67 6. 9 0.27 1. 5 1. 2 8 

236 22 21 24 33.2 34- 3 • .1 118-58.4 15.0 1.6 1 111 3.1 o. 12 1. 9 1. 3 c 

237 22 21 35 31.5 34- 3.3 118-58.7 1.1. 3 1.9 8 159 4.2 o. 12 1. 3 0.8 c 

238 22 22 20 11.0 34- 2.9 118-58.8 13.3 2.0 10 98 4. 4 0.08 (\.6 o. 4 B 

239 23 2 £&4 24.4 34- 4.1 118-58.5 12.6 1. 1 6 174 4.2 0.03 (\.5 1. 1 B 

240 23 6 40 56.4 34- 5.3 118-58.8 1.3.8 1.6 8 71 2.4 0.05 (\.6 1. 4 A 

241 23 8 17 18.8 34- 2.9 118-58.4 12.4 2.9 22 66 2. 3 0.09 (\.4 0.3 A 

242 23 11 52 11.8 34- 4.9 119- 0.6 11.2 1. 4 6 165 2. 5 o. 01 (\.3 0.6 B 

243 23 13 30 20.6 34- 4.1 118-58. 1 12.5 1. 1 6 17 2 3. 6 o. 05 o. 9 1. 7 B 

244 23 21 11 26.1 34- 2.9 119- 0.1 13.4 1. 6 11 159 2. 4 o. 15 1. 3 1.0 c 

245 2.3 23 15 55.0 34- 4.1 118-58.6 12.8 1.5 10 145 1. 0 0.09 ('1.9 o.a B 

246 23 23 30 3. 4 34- 5.1 119-2.1 14.9 1. 5 9 145 0.2 o. 17 1. a 2.0 c 

247 24 1 25 1. 9 34- 3.8 119- 3.4 9.3 2.1 12 168 3. 1 0.20 1. 6 1. 1 c 

248 24 3 49 36.2 34- 4.3 118-58. 1 10.8 1. 6 15 137 1. a 0.06 ('1.3 0.3 B 

249 24 5 31 57.4 34- 4.8 119-0.3 12.6 1.7 13 150 2. 2 0.08 (\.5 0.8 B 

250 24 7 52 19. 1 34- 2.9 118-59.3 15.7 1. 5 13 159 2. 2 0.07 (l.6 0.8 8 

251 24 9 7 4. 4 34- 4.1 118-58.5 15.6 2. 1 22 64 1. 1 o. 12 ('1.6 0.3 A 

252 24 10 55 4.9 34- 3.6 118-59.4 15.0 1. 7 15 189 0.9 0.09 ('.7 0.6 c 

253 24 12 58 58.1 34- 3.4 119- 2.9 11.3 1. a 13 158 3.4 0.09 (l.7 0.1 8 

254 24 13 12 30.6 34- 4.3 118-57. 1 13.6 1. 9 17 64 2. 5 0.05 "· 3 0.2 A 

255 24 13 26 31. 3 34- 3.2 118-58.3 12.0 2.2 21 65 2.0 0.13 ('.6 0.5 A 

256 24 13 48 33.8 34- 4.9 118-57.3 11.8 1.1 10 96 3.3 0.05 ('.4 0.4 8 

257 24 18 ]9 18.0 34- 5.0 119- 0.6 17.7 1. 5 8 146 2. 5 0.02 (\.3 0.5 B 

258 24 20 24 48. 1 J4- 4.1 118-58.5 10.4 1.7 13 146 1. 1 o. 11 r.7 1.0 8 

259 24 22 48 37.6 34- 3.8 118-58.4 10.8 1. 6 13 193 3.9 o. 09 (\.5 0.6 c 

260 25 6 44 37.3 34- 4.7 118-59.1 15. 1 1. 1 12 130 1. 5 0.08 1. 0 1. 6 B 

261 25 10 10 37.6 34- 4.1 118-58.7 9.6 1. 2 14 149 0.8 0.16 1. 4 1. 9 c 

262 26 6 50 39.6 34- 4.1 118-59.8 14.4 2.7 21 64 1. 0 0.12 r.s 0.4 A 

263 26 11 30 21. 1 34- 3.0 118-58.9 14. 1 1. 7 19 66 2.0 0.17 ('.8 0.6 8 

264 26 15 57 57.3 34- 6.4 118-58.2 8.0 1. 5 11 76 3. 7 0.28 ;.3 3.9 8 

265 27 2 10 22.5 34- 2.2 118-59.1 15.7 2.3 22 67 3. 4 0.17 r.7 0.5 B 

266 27 4 19 4.8 34- 4.5 118-58.3 13.8 2. 5 26 64 1. 6 o. 17 r.1 0.5 8 

267 27 8 45 30.9 34- 3.3 118-58.4 13.7 1. 9 17 99 1. 8 o. 15 ('.8 0.1 8 

268 27 11 49 16.2 34- 1.7 118-59.7 11.6 1. 8 15 126 6. 5 o. 13 ('.9 1. 0 8 

269 28 12 36 10.6 34- 2.1 118-59.1 15.5 2.7 27 67 3.7 o. 18 (' .. 7 0.11 B 

270 l'IAR 1 18 41 41.5 34- 3.4 118-59.9 13.5 2.4 20 88 1. 6 o. 18 ('.8 0.6 8 

271 2 7 35 51.0 34- 4.1 119- 1. 4 15.3 1.9 15 157 3. 5 0.17 1. 1 0.8 c 

272 2 14 31 21.0 34- 4.4 118-58.4 14. 1 1. 3 12 125 1.4 o. 12 T. 2 1. 8 B 

273 3 4 44 10.4 33-IJ6.8 119-59.7 12.5 1. 8 5 168 41. 1 0.07 1. 2 1. l c 

274 5 12 55 59.7 34- 2.1 118-58.9 14.9 3.0 27 67 3.6 o. 19 0.7 0.5 B 

275 6 6 21 37.2 33-55.8 118-31. 3 16.0 2.3 11 237 20.4 0.19 1.4 0.8 c 

276 6 19 16 3. 8 34-24.0 119-30.8 10.5 2.1J 6 135 16.0 0.10 1. 4 1. 5 c 

277 1 0 39 2. 0 34- 2.6 118-59.7 15.6 2.5 23 66 5.9 0. 21 0.9 0.5 B 

278 1 12 56 22.5 34- IJ.5 119- 1. 8 13.2 1. 9 18 158 4.9 o. 16 1. 0 0.7 c 

279 7 23 49 51.9 33-49.2 118-41.0 8.0 2.5 12 162 23.3 o. 16 1. 1 8. 3 c 

280 10 1 40 52. 1 34- .3.7 118-57. a 12.9 2.0 22 119 2.3 o. 19 0.8 0.8 p 

20 
Table 2.--List of earthquakes in the western TransvePse Ranges~ Z9?0-?5--continuei 

EVENT fEAR MO~l DY HR fUI SEC LAT N LONG W DEPTH HAG NO GA.i? DMIN BftS E:RH ERZ Q 

281 1973 HAR 10 21 52 37.8 34-15.2 119-43.4 12.2 2.3 5 168 26.9 0.03 C.7 o.8 c 

282 11 19 19 38.0 34-26.4 118-16.9 1. 3 2.2 10 100 18. 1 o. 17 0.9 c 

283 16 22 38 20."i 34- 3.5 118-59.3 12.2 3.0 19 65 5. 2 0.20 C.9 0.7 B 

284 17 0 54 35.7 34- 3.8 118-58.7 12.6 3.3 22 65 1. 0 0.13 o.s 0.3 A 

~85 21 9 27 19.7 34- 5.2 118-59.5 16.2 1. 3 8 12 1 2.2 o. 02 C.l 0.6 8 

286 22 3 49 17.6 34- 4.4 119- 1.8 16.6 1. 6 10 157 4.0 o. 12 1. 3 0.8 c 

287 23 8 32 21.2 34- 4.5 118-58.9 12.6 1. 9 9 95 o. 9 0.03 0.4 o. 4 8 

288 26 1 27 44.9 33-53.7 118-41.2 8. 0 2.5 21 72 16.4 0.17 0.7 1. 1 c 

289 26 9 30 31.3 34- 3.6 118-57.7 11.9 1. 7 10 174 2.4 0.07 0.7 1.0 8 

290 26 9 30 41.2 34- 4.1 118-57.7 11. 3 2. 1 15 149 2. 3 0.10 0.5 0.5 B 

291 26 15 13 25.5 34- 3.4 118-59.1 12.6 2.6 18 65 1. 1 o. 16 0.8 0.6 8 

292 26 15 26 26.6 34- 4.1 118-59.3 11. t 1. 7 13 b7 0.2 o. 11 1. 1 1. 0 8 

293 }.1 0 39 19.0 34- 4.0 119- 1. 1 11. 3 2.0 10 112 3.0 o. 26 2. 1 1. 9 B 

294 28 0 20 11. 3 34-10.6 118-59.5 1. 4 1. 4 6 200 3.2 o. 01 o. 2 o.o c 

295 28 6 29 39.13 34- 3.1} 118-56. q 10.7 1. 0 6 149 1. 8 0.02 0.1 1. 2 8 

296 28 HI 43 53.7 34- 4.7 118-58.4 10.0 1. 6 8 99 1. 8 0.03 0.4 0.6 B 

297 29 17 54 16.9 34-26.6 119-47.0 14.2 3.3 17 80 6. 5 o. 17 0.9 0.6 8 2g~ 29 21 35 33.9 33-58.8 118-32.8 2.4 2.6 23 85 15.2 o. 18 o. 8 8.7 c 299 31 5 33 49.8 34- 2.3 118-46.3 8.0 1. 6 7 172 4.2 o. 21 2.6 5.0 c 

300 31 9 53 26.7 34- 3.7 118-57.6 11.4 1. 5 14 171 2. 5 o. 14 1. 0 0.1 B 

301 APR 2 17 35 9. 1 34- 4.6 118-58.7 10.5 1.3 7 98 1. 4 0.04 0.5 0.8 B 

302 4 23 25 4.4 34- 8.3 118-59.3 10.9 1. 4 6 81 1. 9 0.26 "· 3 4.2 B 

303 4 23 27 30.9 34-23.1 119-3'1.5 11. 6 1.8 5 141 17.7 0.03 0.5 2.0 c 

304 5 a 40 2. 2 34- 2.4 118-59.6 12.0 2.0 13 120 2.2 o. 08 0.6 0.5 B 

305 5 11 4 28.7 34-30.4 119- 4.2 14.4 2.0 5 168 29.4 o. 22 6. 5 4. 5 D 

306 5 11 5 37.6 34-30.3 119- 4.4 15. 1 1. 9 5 168 29. 1 0.10 2.8 2. 1 D 

307 5 lij 35 45.8 34- 4.5 118-59.0 11.8 1. 6 9 93 o. 9 0.07 o.8 1. 3 B 

308 1 21 0 28.3 34- 5.4 11 B-58. 1 11.9 1.7 12 70 3. 2 0.04 0.2 0.2 A 

309 H 1 36 30.0 33-57.3 119-14.3 4.8 1.7 9 161 19.5 0.15 1. 1 12.9 c 

310 8 2 26 30.5 34- 2.3 119- 4.0 10.6 1. 8 15 263 7.9 0.11 0.7 1. 0 c 

311 11 6 0 19.6 34- 5.5 119- 0.9 14. 3 1. 2 8 156 3. 8 0.03 0.6 1. 2 B 

312 12 19 52 1. 4 34- 5.6 119- 1. 1 12.0 1. 6 1 156 4. 1 0.05 0.8 o. 9 8 

313 17 10 15 14.2 33-55.9 119-13.0 4.9 2.0 6 164 22.3 0.14 1. 3 16.6 c 314 17 12 27 4.5 34- 9.3 119-10.2 8.0 1.9 5 151 10.9 0.17 9.0 D 

315 17 15 44 40.4 34-25.7 119-46. 1 1.6 2.1 6 109 9.2 0.02 0.2 0.3 B 

316 19 10 25 30.9 34-40.1 118-45.2 12.7 2.9 12 169 11.2 0.23 1. 5 1. 1 c 317 19 19 29 43.6 33-57.0 118-42.9 1. 9 2. 1 11 149 29.7 o. 20 1. 4 c 318 20 21 14 6.4 33-59.9 118-55.9 1.3 2.1 1 254 17.3 o. 17 2.6 2. 6 D 

319 23 16 15 16. 3 34-25.9 120- 3.3 14.7 2.4 1 82 12.6 0.10 o.8 0.1 A 

320 27 11 57 42.0 311- 0.3 119- 6.7 3. 5 2.2 9 240 12.4 0.19 1. 6 18.9 D 

321 JO 17 18 57.7 34-22.6 119-35.1 1. 0 1. 8 6 134 17.8 0.12 1. 1 1.9 c 

322 MAY 8 14 0 53.6 34-26.0 118-54.9 2.2 2.4 6 132 21.9 0.21 2. 1 c 

323 8 17 18 12. 1 34-25.4 118-54.8 8.0 1. 9 7 128 22.6 o. 43 3.8 c 324 11 2 35 36.3 33-58.4 118-33.0 3.7 2.5 17 130 15.6 0.16 0.7 1.8 c 

325 11 16 30 38.4 34- 9.4 119-11.3 8. 0 2.2 5 146 12.6 0.06 1. 3 s. 3 0 

326 12 21 55 23.3 34- 0.8 119- 1. 9 6.4 3. 1 14 9 1 11. 1 o. 19 1. 0 1. 5 B 

327 h 0 5 40.9 34- 1.9 119- 2.5 10.7 2.2 8 107 8. 8 0. 15 1.3 1. 2 8 

32R 16 2 10 39.4 34-26.7 119-116. 1 12.7 2.3 8 106 5.0 o. 18 1. 6 1. 2 B 

329 16 13 29 36.1 34-18.0 119-47.0 5. 1 1. 7 5 A3 22.7 0.23 2.1 D 

330 19 22 26 2. 6 34-19.4 119-10.8 3. 3 1. 9 5 125 15.9 0.32 2. 3 0 

331 19 22 35 38.9 34-20.1 119-11.3 3. 1 2.0 5 127 1 "· 8 o. 30 1. 6 D 

332 24 3 30 22. 3 33-58.8 119-59.2 0.9 2.0 8 161 16.0 0.11 0.9 c 

33] 30 J 35 47.6 34-20.4 119-20.9 0.2 1. 9 5 125 3. 1 0.25 3. 5 3.8 D 

B4 JU:i 5 5 9 50.6 34-25.8 118-35. 8 0.6 2.5 9 10 1 16.8 o. 12 0.7 c 

335 5 6 35 4.2 3 4-1 a. 1 11q-s6. o 17.5 1. 6 6 99 29.6 o. 12 1. 6 14.9 c 

336 6 3 14 1 o. 9 34-19.2 119- 12.6 5. q 2.5 10 109 13.5 o. 19 1. 1 1. 5 c 

337 8 19 115 28. 1 34-11.8 120- 0.8 4.2 1. 7 6 118 35.8 0.24 2.0 c 

338 15 5 27 13.6 JJ-59.8 119- 9.6 8.0 2.4 7 1113 15. 3 0.06 0.8 1. 6 B 

Jl9 21 7 9 6.0 34- 3.2 118-50. 1 3.6 1.4 6 137 6.0 o. 11 0.6 6. 1 c 

l40 22 21 47 14.9 34- 3.3 118-48.1 1. 5 1.7 6 174 5.7 o. 11 3.3 2.9 c 

21 
Table 2.--List of earthquakes in the western Transverse Ranges, l9?0-?5--continued 

EVENT YEA~ MON DY HR MN SEC LAT N LONG li DEPTH fUG NO GAP DftiN Rf!S F~H ERZ Q 

341 1973 JUJ 22 22 59 52.f' 33-4 5.3 120- 5.8 6.6 2.5 7 18 8 39.2 0.16 1. 6 1. 6 c 

342 27 7 20 50.6 34- 3.0 118-59.5 2.0 1. 9 9 131 2.7 o. 10 c.8 o.c; B 

343 JUL 5 21 53 41i.O 34- 3.5 119- 1. 1 13.3 2. 1 9 121 2.4 0. 11 1. 0 0.6 H 

344 8 5 18 38.0 34- 3.6 118-59.4 12.2 2.0 12 ~4 3. 5 o. 11 C.1 0.6 A 

145 14 5 48 6.7 34- 0.7 118-49.2 13.5 2.0 13 91 1. 5 0.14 1. 0 0.8 B 

346 14 A 6 57.fi 34- 2.1 119- 2.0 1 3. 1 2.0 13 166 1. 5 o. 15 T. 0 1. 0 c 

347 15 12 19 24.3 34- 4.0 119- 3.8 17.6 1. 6 10 133 4. 8 0.08 C.1 0.7 B 

)4~ 15 19 54 1. 3 34-22.1 118-31. 3 14.8 1. 8 14 86 11.5 0.13 C.1 0.7 A 

149 16 15 43 56.2 34-17.8 119-51.9 16.3 1.6 6 91 26.2 0.08 1. 2 1. 5 B 

350 18 6 9 30.9 34- 2.1 118-44.4 5.7 1. 6 10 167 7.0 0.23 T. 8 2.7 c 

351 24 6 57 25.9 34- 2.3 119- 1. 1 12.5 2.5 2 1 66 o. 2 o. 22 ('.9 0.7 B 

352 25 16 16 35.4 34-43.0 119- 3.5 3.3 1. 9 12 232 33.4 o. 27 2.4 0 

3'>1 2(; 22 17 48.5 33-59.7 118-43.9 2.4 1. 6 8 289 1.0 0.15 ~.8 3. 5 D 

354 29 7 57 12.7 34- 3.2 118-57.6 11.8 2.3 15 98 3. 9 0.17 ('.9 0.8 B 

355 A!J<.i J 3 9 0.4 34-17 .o 119-51.8 13.5 1. 7 8 151 27.4 o. 19 1. 5 1. 6 c 

356 3 23 32 55. 9 34- 3.7 119- 5.0 16.2 1. 6 12 146 5.6 0. 12 1. 0 0.7 B 

157 6 2J 29 16.8 33-58.3 119-27.1 13.8 5.0 16 97 4.8 o. 11 ('.6 o. 4 B 

158 6 23 47 35.5 33-58.9 119-27. 3 12.9 1. 9 111 96 3. 8 0.14 C'.7 0.7 B 

359 6 23 53 46.4 33-58.9 119-27.1 13.7 1. 9 14 96 3.6 0.10 (\.5 0.4 B 

360 7 0 16 59.4 33-58.7 119-26.9 12.9 1. 4 11 201 3. 9 0.12 1. 1 1. 1 c 

361 7 1 40 50.3 33-59.2 119-26.8 14.9 1. 9 12 102 3. 1 0.12 (\.8 0.5 B 

362 10 19 30 38.3 34-11.3 118-58.4 1. 6 1. 1 7 121 1. 5 o. 14 1. 2 o. 5 B 

363 13 23 2 39.5 34- 2.8 118-58.8 15.8 1.9 14 145 3.6 0. 19 1. 3 0.6 c 

364 15 0 38 9.3 34-27 .o 119- 3. 1 8.0 1. 6 12 173 14.5 0.19 1. 0 5.3 c 

365 15 2 16 21.9 34-20.5 119-20.7 "· 3 3.0 15 148 3. 1 0.22 1. 3 1. 8 c 

366 16 21 10 18.2 33-58.0 119-27. 1 13. 1 1. 7 10 110 5.3 o. 09 ('.6 0.5 B 

367 16 23 24 6.9 34- 3.7 118-48.8 2.6 1. 4 9 163 6. 4 o. 16 1. 1 c 

368 17 15 46 56.3 34-26.B 119-13.0 12. 1 1. 6 9 156 4.3 o. 10 (\.7 1. 1 B 

369 19 9 22 50.5 34- 3.9 119- 2. 3 7.5 1. 8 11 159 3.7 o. 11 (\. 9 1.2 E 

370 20 13 32 57.8 33-57.2 119-10.2 9.9 1.8 11 143 17.0 0.11 1. 0 2.0 c 

371 20 14 1 49.3 33-57.4 119-10.6 8.0 2.5 21 73 17. 1 0.12 (\.5 0.7 B 

372 21 5 29 23.4 34- 4.4 118-59.8 11.7 1. 3 7 132 3. 4 0.07 1. 0 0.7 B 

373 22 19 27 38.4 34-16.2 119-44.7 14.4 2.2 8 206 25.4 0.15 1. 9 1.3 c 

374 23 8 8 17.5 34- 4.5 119- 4.3 17.8 1.8 8 129 3. 9 0.08 o. 9 0.9 B 

375 23 8 20 8.3 34- 3.1 118-57.9 12.5 1. 8 8 140 4.0 o. 11 1. 1 1. 1 c 

376 24 9 4 55.4 34-2 5.9 119-13.0 13.4 2.4 17 152 2.8 0.20 1. 1 0.9 c 

377 25 5 27 10.f 34-17.0 119-39.0 1 o. 9 2.4 9 150 24.3 o. 11 0.9 1. 1 B 

378 27 19 56 19.<l 34- 2.8 118-59.4 3.6 2.0 10 159 5.2 o. 15 1. 3 4.5 c 

379 27 20 5 44.0 34- 2.5 118-59. 2 2.6 1. 9 9 213 5. 7 0.20 1.9 1. 7 c 

380 l8 21 57 30.2 34- 2.7 118-47.4 6.0 1. 5 8 128 4. 7 o. 12 1. 3 3. 3 B 

381 29 10 27 23.5 34- 3.1 118-59.9 2.4 , • 8 9 119 2. 4 o. 07 0.7 0.4 B 

3P.2 30 14 3 22. 3 34-11.2 119-7.3 2.2 1. 4 10 171 10. 1 o. 17 1. 2 1. 4 c 

383 31 1 24 33.7 34-23.5 119-22.2 10.8 2.2 15 141 3. 4 o. 12 0.7 0.6 B 

384 31 5 42 32.3 34-23.4 119-22.2 9.8 1.9 12 141 3. 4 0.12 (\.6 1. 0 B 

3R5 SE? 2 6 28 3.9 34- 1 • 1 118-44.9 13.9 2.3 17 100 5.6 o. 16 o. 9 0.6 B 

186 2 8 35 15.9 34-26.2 119-45.6 11.0 2.0 11 162 8.0 0.13 1. 2 0.9 c 

387 3 12 21 51. 4 34- 2 .o 118-50. 4 13.7 1. 2 9 135 4.5 0.08 fl. 8 1. 4 B 

188 4 9 11 25.9 34-23.3 119-21.8 11. 5 3. 4 22 113 2.8 o. 19 0.7 0.7 B 

389 4 9 28 2(}.5 34-23.0 119-22.6 10.5 1. 8 11 139 3. 5 0.13 0.9 1. 2 B 

39:) 4 22 16 53.0 34- 2.2 118-48.1 6.1 1. 7 7 119 3.7 0.10 1. 4 3.0 B 

391 7 15 18 10.8 34-22.8 119-22. 1 9.9 2.6 13 120 2. 6 0.18 1. 0 1. 1 B 

392 7 15 18 58.4 34-22.5 119-21.6 0.5 2.0 8 219 1.6 0.15 1. 5 0.5 c 

393 7 15 19 56.8 34-23.5 119-21.9 1 o. 6 1. 9 11 141 3.3 o. 14 o. 8 1. 3 B 

394 d 4 13 53.9 34-26.3 119-13.6 1 s. 6 1.8 12 154 13.2 o. 14 1. 2 0.8 c 

395 13 12 51 41.3 34-27.7 119-12.8 12.0 1.5 12 160 15.8 0.20 1. 2 3.9 c 

396 13 13 1 'J5.4 34-26.3 119-13.0 12. 1 2.1 14 15 4 14.0 0.18 1. 1 1. 7 c 

397 13 13 8 37.9 34-26.7 119-14.3 16.0 2. 2 16 156 12.9 0.13 o. 9 0.6 B 

398 15 23 4 50.4 34-19.6 118-34.6 9.3 1. 8 13 , 1 3 5.6 0.12 0.1 1. 2 B 

399 20 11 31 20.7 34-27.7 118-34.3 11.6 1. 4 12 215 17.7 o. 26 3.0 3.4 D 

400 20 22 1 44.9 34- 1.0 119- 0.7 11. 1 2.0 19 68 2.2 o. 12 o. 5 0.6 A 

22 
Table 2.--List of earthquakes in the western Transverse Ranges 3 l970-75--0ontinuerl 

EVENT YEAR !10N j)Y HP. liN SEC LAT N LONG w DEPTH tUG NO GAP DfUN RptS .ERR ERZ Q 

401 1973 SEP 26 3 56 11.5 34-30 .o 118-49.7 8.0 1. 8 10 154 10.9 0.28 2.7 10.9 c 

402 ocr 4 22 6 3. 1 34-10.7 119- 7.8 12.8 1.4 10 95 9.8 o. 12 0.9 1. 1 B 

403 6 16 4 47.9 34- 2.0 119- 0.6 8.0 1. 8 17 185 0.7 o. 14 0.7 o. 9 c 

404 9 1 11 46.~ 34-28.0 119-29.2 8.0 1. 7 14 162 17.0 0.17 0.9 1. 5 c 

405 10 22 3 13.8 34- 3.2 118-47.8 1. 1 1. 3 6 113 5. 5 0.05 0.9 1.0 8 

LJ06 12 4 25 18. 1 34- 3.2 118-53.9 10.7 2.2 17 113 5.7 0.14 0.7 0.7 B 

407 15 8 11 52.1 34-22.9 119-44.0 1 o. 1 2.1 16 68 6.8 o. 13 o. 7 0.6 A 

408 15 21 57 6.3 34- 3.0 118-47.7 2.2 1. 1 7 118 5. 1 0.06 0.5 c 

409 16 23 37 33.2 34-10.6 119- o. 4 1. 2 1. 3 7 129 1. 9 0.06 0.5 0.3 8 

410 21 3 45 43.4 34- 4.7 118-57.9 14.6 1. 1 9 136 1. 2 0.12 1. 2 1. 1 c 

411 24 21 45 14. 9 34- 2.6 118-47.9 6.0 1. 1 6 119 4. 3 0.07 1. 2 3. 2 B 

412 25 19 24 43.3 34-10.6 119- 0.4 1. 1 1.3 8 128 1. 9 0.06 0.4 o. 3 B 

ll13 26 16 45 11.7 34- 1.9 118-53.9 4.5 1.9 8 163 7. 9 0.03 o. 3 1. 4 B 

414 30 14 51 5. 1 34- 2.5 118-58.8 14. 1 1.3 9 155 3.4 0.07 1. 0 1.5 B 

415 NOV 1 22 43 59.2 34-17.6 119-30.6 4. 7 2.0 11 102 17.4 0.14 0.7 10.a c 

416 6 16 16 1. R 34- 2.4 119- 1.2 16.4 1. 4 9 125 o. 4 0.05 0.6 0.4 8 

417 8 23 15 15. 4 34- 2.9 118-47.9 4.9 1. 0 7 114 5.0 0.05 0.7 2. 4 8 

418 14 11 15 31. 4 34-17 .o 118-3 2. 9 13. 1 2.2 18 148 4.3 0.19 1.0 o. 9 c 

419 15 1 4 28.t; 34-10.6 119- 0.5 1. 1 1.0 1 131 2. 0 o. 03 0.3 0.2 B 

420 25 15 :+2 52.3 34-11.CJ 119- t.5 18.5 1. 6 11 92 9.a 0.10 0.8 1. 0 B 

421 27 7 9 31.0 33-59.0 119-14.2 2.1 1. 7 12 12 3 18. a 0.13 0.8 c 

422 DEC 5 19 29 53.2 34- 3.7 119- 2.5 7. 9 1.4 12 120 3.6 o. 11 0 .. 7 o.a B 

1123 7 12 0 15.2 33-48.5 120- 0.4 11.9 2.5 8 165 40.2 0.22 2. 5 1. a c 

424 12 10 1 :n. 9 34- 4.1 118-58.8 12.3 1. 8 11 136 2.6 0.15 1. 2 0.7 c 

425 111 19 21 31.0 34-24.8 118-34.7 8.0 1. 7 9 124 15.0 0.15 1 .. 0 4.6 B 

426 20 14 23 21.4 34- 4.4 118-56.0 13.3 2. 1 18 64 3. 3 o. 18 0 .. 8 o. 7 8 

427 24 6 23 44.0 34-15.1 118-Jf-.8 6. 5 1. a 10 10 5 3. 5 o. 15 0.9 1.4 B 

428 25 6 9 3.6 34-21.2 118-32.2 11. 3 2. 1 12 109 9. 9 o. 13 0.1 1. 2 B 

429 25 17 0 34.6 34-15.1 118-34.3 o. 1 1. 2 d 71 3. 3 o. 19 1. 2 1. 3 B 

430 26 10 23 50.6 34-25.6 118-34.3 2.8 1. 5 8 149 16.3 o. 14 1. 3 c 

4~1 2H 23 15 15. 3 34- 3 -, •"- 118-47.8 2.4 1. 3 7 114 5. 5 o.os 0.7 c 

432 30 19 14 20.6 J3-5g.3 118-46. 3 16.3 1.7 9 249 15.7 o. 10 1. 5 1. 7 c 

4B 19 7~ JAN 9 20 2 ~4.6 34-10.b 119- 0. 1 1.4 1. 5 6 123 1. 5 o. 03 o. 4 o. 2 8 

434 10 18 41 59.8 34- 3.6 119- 3.3 13.7 2. 1 12 117 4. 4 0.20 1. 6 1.0 8 

415 10 22 26 17.8 34- 5.5 119- 0.8 11.3 1. 5 8 109 4. 5 0.06 0.6 0.9 B 

4~6 12 2 24 9.~ 34- 3.8 118-57.9 15.7 2.2 9 154 10.5 0.20 1. 5 0.9 c 

4"17 17 d 0 15.3 34- 5.7 119- 2.7 13.8 1. 5 8 155 2. 4 0.07 1. 4 2. 1 c 

4'38 18 17 8 16.5 34- 5.1 118-51.8 17.2 1. 5 8 100 2.4 0.05 0.6 1. 1 B 

439 L1 18 35 55.7 34-30.7 118-42. 2 15.7 1. 8 14 145 7. 1 o. 12 0.8 0.5 B 

4~0 23 1 43 35.4 34-15.7 119-45.6 <}.7 2.2 9 104 31.8 o. 12 0.9 0.9 8 

441 25 5 2 25.3 34- 3.6 118-54.2 12.7 1.2 8 132 5.2 0.04 0.4 0.8 8 

442 25 7 27 21.4 33-55.0 118-42.9 8.0 1. 9 14 221 12.9 0.13 0.9 3.0 c 

443 FEB 1 18 57 32.7 34- 3.7 119- 0.3 2. 3 1.3 a 166 3.0 0.09 1. 7 1. 2 c 

444 1 23 58 35.5 34- 2.3 119- 0.3 8. 0 1. 5 10 158 1. 1 o. 13 1. 2 1. 4 c 

IJ45 14 12 33 16. 1 34-29.4 119- 4.9 12.4 1. 8 13 14a 27.5 o. 17 0.9 1. 1 c 

446 20 5 1a 14.9 33-57.3 119-26.7 11. 3 2. 1 13 113 6. 6 o. 17 1. 0 o. 8 8 

447 22 12 49 4R.4 34-16.4 119-31.0 12.2 1. a 6 125 19. 1 0.04 0.4 0.7 8 

448 23 8 34 36.2 34- 3.3 118-56.3 14.9 1. 3 1 139 4. 4 o. 14 2. 0 2.2 c 

449 27 12 25 36.6 31+-15.6 119-31.0 8. 0 2.3 15 87 20.0 0.22 0.9 1. 2 c 

450 MAH 3 16 29 1. 8 34-20 .o 118-34.7 12.9 2.2 10 172 6.2 0.15 1. 2 1. 9 c 

451 3 16 32 35. 1 34- 2.0 118-59.6 9.2 2.3 14 129 2. 1 o. 17 1.0 0.8 B 

452 3 16 59 23.4 34- 3.3 119- 0.3 8.9 2.3 14 93 2. 3 0.25 1. 5 1. 1 B 

453 4 0 34 12.7 34-20.9 118-31. 2 10.4 1. 6 9 191 10.5 0.05 0.5 0.7 c 

454 4 0 41 8.7 34-21.1 118-31.2 10.3 1. 3 8 109 10.6 0.06 0.5 1. 1 8 

IJ55 7 6 29 8.3 33-55.5 118-42.6 8.0 1. 9 11 154 12.4 0.20 1. 2 2. 4 c 

456 10 12 34 30.1 33-51.7 120- 2.8 1 o. 9 1.8 11 161 34.2 o. 18 1. 0 0.9 c 

IJ57 12 3 3 13. 3 34-23.2 118-34.7 2.0 1. 1 10 126 12.2 0.22 1. 4 c 

458 17 3 12 44.3 34- 3.5 1 1a-59. R 1. 9 1.5 8 110 3. 1 0.06 0.4 0.2 B 

IJ59 18 2 37 25.8 34- 2.a 118-54.7 12.7 2.0 15 96 6.7 o. 12 0.7 0.6 8 

460 28 18 20 31.3 33-51.'1 119-23.0 1. 8 1. 7 8 132 17.1 0.12 0.8 c 

23 
Table 2.--List of earthquakes in the western Transverse Ranges3 l970-75--Cbntinue1 

EV?.NT lEAR HO~ OY HR MN SEC LAT .N LONG Ii DEPTH rtAG NO GAP DrtiN RPIS f-RH ERZ Q 

ij61 1974 MAR 30 1 12 36.2 34- 5.1 118-50.8 13. 1 1. 8 11 94 3. 6 o. 13 1. 0 1. 0 B 

462 31 11 20 47.7 34- 1.2 118-44.9 5.9 2.6 16 80 5.6 0.09 ().4 0.6 A 

463 APR 1 19 56 13.3 34- 4.1 119-59.5 14.5 2.2 17 64 3.5 o. 14 C'.1 0.4 A 

464 2 9 46 30.2 34- 3.1 118-57.9 13.7 1. 5 8 16a 4.2 o. 09 1.5 1. 0 c 

465 2 10 16 59. 1 34-2q .B 11a-46.1 14.0 2.0 8 10a 8. 4 o. 09 ('.9 0.6 B 

466 3 10 46 21.7 34- 3.3 11ti-5].8 11.3 2. 5 14 a a 5. 4 o. 13 C'.1 0.1 A 

467 5 1 39 37.8 34- 2.8 118-56. 3 11.4 2.5 14 100 5. 3 0.09 ('.5 0.5 B 

468 11 8 0 58.0 34- 4.2 119- 0.6 1 r;. 7 1.4 6 122 3. 8 0.02 ('.5 0.9 B 

469 h 10 29 15. 2 34- 5.7 119- 2.4 19.2 1. 6 10 94 2. 8 0.08 ('.8 o. 6 B 

470 22 14 53 34.3 34-17.8 118-32.6 9.4 2. 1 13 153 5. 1 0.22 1. 5 2.3 c 

471 24 0 9 16.2 34- 5.7 118-51.7 1. 7 1. 2 8 92 1. 8 o. 11 ('.6 0.3 B 

472 25 8 23 53.5 34- 1.5 119- 5.8 8. 9 2.8 14 159 1.6 o. 11 ('.7 o. 8 B 

47J 25 8 28 42. 3 34- 1.8 119- 5.0 9.9 1. 9 16 190 6.2 o. 15 ('.9 0.1 c 

474 MAl 1 6 2 30.6 34-23.7 119-46.8 9.6 2. 1 11 96 12.9 0.26 1. 7 1. 9 B 

475 10 22 21 29.5 34- J.q 118-54.3 13.8 1. 1 8 128 6.2 0.06 (',6 1. 1 B 

476 11 16 22 13. 3 34-26.2 118-35.4 11.9 1. 5 12 205 11.5 o. 1 q ('.9 1. a c 

477 22 1CJ 46 44.0 34- 3.1 118-58.6 14.1 1. 5 11 137 4. 1 o. 15 1.0 1. 5 c 

478 22 23 39 48.4 34- 2.3 119- o.o 9.0 1. 4 8 161 1. 5 0.10 1. 0 1. 5 B 

479 28 9 55 0.5 34-24.5 119-56.6 20.8 2.0 7 118 54.0 0.20 2'.2 3. 0 c 

480 JU!.i 21 2 5 18. 1 34- 5.5 119- 1. 1 15.8 2.3 11 89 4.7 o. 11 C.1 0.3 A 

481 J(JJ:. 6 21 36 59.1 34- 2.8 119- 1. 8 16.4 1. 8 12 129 1. 6 o. 08 ().6 0.4 B 

482 9 0 58 49.3 34-14.2 119-40.6 10.9 2.0 14 79 22.9 0.26 1. 1 1. 7 c 

4B3 12 6 27 44.2 34- 0.4 118-48.9 9.8 1. 9 16 177 0.8 0.23 1.6 1. 3 c 

484 23 5 31 30.8 34- J.g 118-58.8 14.2 1. 5 q 117 3.2 a. 01 0.9 1. 5 B 

485 25 16 13 41.8 33-56.2 118-51.7 1.2 2.3 12 226 9.2 o. 13 1. 5 1.1 c 

486 26 23 27 51.7 34-10.4 119- 0.4 1. 1 1. 0 6 12a 2. 1 0.03 ().3 o. 2 B 

487 ~UG 12 1 43 27.3 34-15.9 119-42.9 9.1 2.1 11 a1 19.6 0.13 0.7 1. 3 B 

488 12 11 6 25. 1 34-16.5 119-" 1. 2 7.5 1 .. 9 6 14 5 18.6 0.03 o.s 0.8 B 

489 12 19 28 1 o. 6 34-15.9 119-43.2 2.8 2. 4 9 81 19.5 0.21 1. 3 c 

490 19 7 33 48.6 34-16 • .2 119- ]8. 9 14.3 1. 9 7 118 25.a o. 14 1. 1 1. 2 B 

491 25 0 46 30.6 JJ-56 .2 118-40.3 10.8 2.0 11 230 14.5 0.09 1. 0 1. 7 c 

492 30 11 57 48.1 34-21 .7 119-20.6 3. 3 1. 9 a 139 0.7 o. 11 3.9 5.0 c 

493 SEP 6 14 40 43. 1 34-18.9 118-10.7 11.4 2.4 10 112 27.8 o. 19 1. 3 12.2 c 

494 7 23 40 35.0 34-18.4 118-31. 1 6.8 2. 1 12 106 1.1 o. 11 0.6 1. 1 B 

495 9 1 28 22.9 34-22.1 119-19.9 5.6 1. 3 10 178 1. 2 0.10 0.7 0.1 8 

496 9 3 41 46.8 34-22.6 119-19.1 6. 0 1. 4 10 136 2.4 o. 11 0.7 1.0 B 

497 9 4 22 55.4 34-22.8 119-19.6 6.9 1. 7 11 138 1. 9 0.10 0.6 0.9 B 

4<}8 9 22 5 50.7 34-22.2 119-19.7 6. 1 1.4 11 179 1. 4 0.09 0.1 0.7 B 

499 10 1 42 3 3. 2 34-22.5 119-19.5 5.8 1. 9 12 138 1. 9 0.09 0.5 0.8 B 

500 10 3 54 39.7 34-22.2 119-19.5 6.7 1. 5 12 136 1.1 0.08 o. 3 0.6 B 

501 10 10 1 18. 1 34-21.2 11<}-20. 3 7.2 1. 7 13 140 2.0 o. 14 0.7 1. 1 B 

502 13 3 55 2. 6 34-21.9 119-20.0 5.3 1. 5 8 177 1. 0 0.05 0.5 o. 5 B 

503 13 3 56 24.9 34-22.4 119-20.0 6.0 1. 6 11 137 1. 1 0.07 0.4 0.5 B 

504 11 7 10 54.3 34-23.0 119-19.2 7.0 1. 6 11 139 2. 7 o. 15 0.9 1.3 c 

505 23 2 22 5q.6 34-22.7 119-19.4 6.5 2.0 16 138 2.2 o. 13 0.6 o. 9 B 

506 23 2 28 6.7 34-22.9 119-20.1 6.4 1. 8 13 139 1. 6 o. 13 0.7 1. 0 B 

507 24 2 21 49. 3 34-29 .o 119- 3.8 17.2 2.3 18 158 3. 7 o. 19 1. 0 1. 4 c 

508 26 19 58 33.2 34-22.8 11<}-19.3 2.7 1. q 9 138 2.4 0.12 1. 0 10.5 c 

509 OCT 8 0 56 4. 4 34- 2 .. ] 118-59.0 2. 1 3. 4 14 106 3. 1 0.27 1. 3 0.8 B 

510 8 1 2 39.9 34- 3.4 119- o.o 1. 7 1. 4 6 105 2. 8 o. 04 o. 3 0.1 B 

511 8 7 49.8 34- 3.4 118-59.& 1. 9 1. q 7 111 2. 9 0.04 0.3 0. 1 B 

512 8 8 53.4 34- 3.6 118-59.9 1. 9 1. 7 7 104 3.0 0.04 o. 3 o. 1 8 

513 8 11 1 o. 1 34- 3.7 119- 0.1 1.6 1. 2 6 105 3. 1 0.06 0.5 0.2 B 

514 8 17 9.5 34- 3.4 118-59.8 2. 1 1. 7 1 113 2. 9 0.04 0.6 o. 4 B 

515 8 34 54.9 34- 3.b 119- o.o 1. 9 1. 6 7 103 2.9 0.05 0.3 o. 1 B 

516 8 1 50 7.4 34- 3.4 118-r;9.9 1.8 1. 5 7 109 2. 8 0.06 0.3 0.1 B 

517 8 2 30 21. 1 34- 3.4 118-59.5 2.0 1.7 7 118 3. 2 0. OJ 0.2 o. 1 B 

518 8 3 0 16. 9 34- 3.5 118-59.6 2.0 1. 7 7 112 3. 2 0.06 0.4 0.2 B 

519 8 5 59 5.9 34- 3.5 118-59.4 2.0 1. 5 5 116 3. 4 0.01 o.o o.o c 

520 8 11 35 58. 1 34- 3.3 118-'>9. 8 2. 5 1. 5 7 115 2. 7 0.05 0.4 c 

24 
Table 2 .-List of earthquakes in the western Transverse Ranges, ~9?0-?5--continued 

EVENT n.aa MON DY HR MN SEC LAT N LCNG w DEPTH MAG NO GAP DMIB R~S ERH ERZ Q 

C:,J!1 1974 OCT 9 9 25 57.4 34- 1.2 118-59.9 2. 1 1. 1 6 116 2.6 0.06 0.9 0.6 B 

522 9 q 26 57.3 34- 3.5 1 18-59.9 1. 7 1. 1 7 106 2. 9 0.03 0.2 o. 1 B 

5/3 g 9 28 9.5 34- 3.1 118-59.6 2.0 1. 1 6 119 2. 9 0.06 1. 0 0.7 B 

524 9 21 42 41.0 JU- 3.5 118-59.6 2.2 1.7 8 109 3. 0 0.06 0.6 0.5 B 

525 1() 1A ':1 50.7 34- 3.b 118-59.7 1.9 1.3 7 132 3. 3 0.05 0.4 o. 1 B 

526 12 9 54 57.4 34- 1.3 118-59. 3 3. 3 2.9 17 68 3. 4 0. 14 0.6 1. 7 A 

527 12 10 9 39.9 34- 4.5 118-59. 3 4.4 1. 6 9 97 2. 7 o. 15 1. 0 2.0 B 

528 12 10 11 19.4 34- 3.5 119-59.8 1. 9 1. 8 8 109 3. 1 0.05 o. 3 0. 1 B 

S29 12 10 ;s 8. 1 34- 2.9 119- 0.3 1. 2 1.0 7 113 1. 6 o. 08 o. 5 0.2 B 

5'30 15 22 40 30. 1 34-10.2 118-5Y.9 1. 1 1. 6 9 149 1. 7 0.04 0.5 0.3 B 

531 18 23 25 24.6 34- 3.5 119- 0.2 1. 7 1. 2 7 107 2.1 0.04 0.3 o. 1 B 

532 22 0 6 24.1 34- 3.4 119- 0.4 2. 3 1. 1 7 118 2. 4 0.05 o. 8 o. 5 B 

5'33 NOV 6 0 31 2.2 34- 3.3 118-59.9 3.9 1. 1 7 111 2.6 0.05 0.5 1. J B 

5~4 11 5 47 56.6 34- 3.9 11A-59. 6 14. g 1.6 10 10 4 3. 7 0.06 0.6 0.5 B 

515 14 9 41 1. 4 34- 3.6 118-59.9 1. 9 1. 3 7 106 3. 1 0.04 0.3 0.1 B 

536 14 9 51 5.2 34- 3.5 118-59.9 1. 9 1. 0 7 106 2. 9 o. 06 0.4 0.2 B 

531 14 1 1 4 48.3 34- 3.6 118-59.9 1. 9 1.0 7 10 5 3. 2 0.05 0.3 0.1 B 

518 15 6 25 32.0 34- 3.3 119- 0.2 2. 1 1. 2 7 106 2.4 0.03 0.4 0.3 B 

539 17 3 47 22.0 34-22.5 119-40.9 6.3 1. 8 13 88 13.7 0.22 1. 2 8.3 c 

540 27 18 37 18.6 34- 5.3 118-'57.9 16.8 1. 4 8 98 o. 1 0.03 0.4 0.6 B 

541 DEC 1 11 28 37.2 34-25.6 118-34.2 o. 5 2.1 8 112 16.2 o. 15 1.0 c 

542 4 20 12 23.0 34- 4.0 119- 0.1 14.7 1.2 6 134 l. 6 0.04 0.9 1. 5 B 

543 7 7 12 7.7 34- 5.4 119- 0.4 8.0 1. 0 6 104 4. 0 o. 34 4. 4 9.9 c 

544 9 22 29 25.3 34-10.4 119- 0.7 0.7 1. 1 9 134 2. 5 0.09 0.6 0.5 B 

545 l<J 7 57 2.9 34- 3.8 118-44.5 4.0 1. 3 8 148 7.3 o. 17 1. 1 10.1 c 

546 20 10 22 31.0 34-2 3.6 119-41.5 13.3 1.8 9 113 11.6 o. 12 1. 0 0.9 B 

547 20 14 23 19.0 34- 5.5 118-52.0 12.5 2. 1 12 72 1. 7 o. 13 0.8 0.8 A 

548 25 1 1 16 38.2 34- 2.3 119- 0.5 8.7 1.8 7 196 0.8 o. 09 1. 7 1.1 c 

549 27 12 19 46.8 34-17 .I) 120- 3.2 11.8 2. 5 12 127 27.0 0.20 1.2 1. 1 c 

550 29 22 10 4. 1 34-15.1 11<}- 36.5 8.0 2.1 7 87 27.6 0.18 1. 4 4.6 c 

551 29 22 37 0.9 34-11) .6 119- 35. 8 15. 3 1. 9 ~ 87 26.2 o. 10 0.8 0.8 B 

552 1975 JLi 7 4 44 53. 1 34- 6.'3 119- 1. 5 17.3 1.2 9 139 6. 2 0.05 0.6 0.4 8 

553 11 14 44 18. 4 33-59 -~ 118-51.7 13.0 2.5 14 157 5. 4 0.12 0.8 0.5 8 

554 19 2 35 9.4 34-2 3.9 119-22. 1 10.3 1. 1 8 147 4.0 0.13 1. 1 0.9 c 

55'1 23 3 48 42.4 33-1)3 .1 118-41. q 8.0 2. 8 26 1)4 15. 3 o .. 16 0.6 0.8 8 

5c;b 2~ 11 1 53.7 34- 1 .4 t 19- 1 • 1 10. 9 2 .. 1 13 112 1. 5 o. 11 0.8 0.7 B 

557 28 5 22 22.7 34-10.9 118-38. 3 8.0 2.4 14 149 1 1. 4 0.21 1. 3 2. 1 c 

SSR 2d 9 45 49.9 34-16.8 119-3 7. 4 8.0 2.5 19 82 19.6 0.23 0.9 1. 2 c s~~q 29 6 8 56.3 34-25.5 119- 19. 1 11. 1 , • 2 9 158 6.7 0.08 0.6 0.9 B 

5f0 30 12 18 52.8 33-59.8 119-10.2 8. 1 1.4 14 19 1 15.8 o. 12 1. 0 1. 8 c 

561 3 1 5 17 57.2 34-17.1 119-38.2 8.0 1. 3 7 16 4 24.6 0.23 2.7 c 

5o2 f25 "' 15 27 23.4 3"- 3.9 118-47.6 8. 3 1. 4 9 108 6.8 o. 13 1. 1 2.7 B 

5(· 3 8 17 36 34.5 34- 4.0 110-4 7. 2 7.0 1. 8 12 113 7. 2 o. 15 0.9 1. 9 B 

5f4 14 22 14 44.2 33-57.2 119-38. 1 8. 9 1. t 13 202 4. 6 0.23 2. 1 1. 6 c 

5t5 16 5 0 45.1 3 3-49. '3 118-49.9 8.0 1. 8 12 280 19.6 o. 12 1. 9 2. 2 c 

566 23 10 21 59.0 34- 3.8 118-59. 1 13.] 2.7 21 54 3. 4 o. 20 0.9 0.6 B 

C)f7 26 6 20 5.7 34-25.1 119-56.8 1 o. 9 1. 7 12 82 12.4 0.24 1. 3 1. 7 8 

56'3 26 6 53 18. 7 34-25.0 119-56. 1 11. 1 1. 9 7 84 12.8 0.06 0.6 0.8 B 

5~9 27 7 31 50.4 34-25.6 119-57. 3 2.5 1. 4 7 140 23.5 o. 14 1. 3 1. 6 c 

570 :11\R 1 5 45 4.2 34- 1.2 11R-43.2 6.6 2.0 13 85 8. 1 o. 14 0.7 1. 1 B 

'171 15 0 6 1 o. 3 34-26.7 119-16.7 11. 4 2. 0 14 156 10.4 o. 14 0.6 1. 1 B 

572 15 1 25 26. 1 34-26.7 119-17. 1 13.5 1. 1 10 167 10. 1 0.09 0.7 0.8 B 

57~ 17 16 29 25.7 34-31.8 118-53.8 16.2 3.0 20 147 15.0 o. 17 0.8 o. 7 c 

574 23 22 ij2 28.1 33-55.9 119-39.4 1 o. 2 1. 9 11 111 7. 3 o. 10 0.7 0.6 B 

575 24 10 32 25.1 34-30.1 118-53. 1 12.2 2.7 16 111 15. 2 o. 16 0.6 0.7 B 

576 Ai?R 10 21 19 26.6 34-29.2 118-50.4 6.7 2. 1 12 133 12.8 o. 20 1. 1 2. 5 B 

577 11 3 31 40.7 34-21.1 119-19. 3 , 1. 8 1.6 13 159 9.5 0.16 1. 0 1.2 c 57R 1 1 21 6 5. 5 34- 3.1 118-59.8 9.6 3. 1 22 47 2.5 0.18 C.6 0.6 B 

57g 12 6 37 5.9 34- 3.2 118-'59.5 11.9 2. 1 13 100 3. 0 0.17 1. 0 1. 0 B 

SRO 14 4 55 8.2 34- 2.0 119- 1. 5 16.6 1.7 12 166 0.9 o. 21 T. 5 0.8 c 

25 
Table 2.--List of earthquakes in the western Transverse Ranges, Z9?0-?5--Continuei 

EVENT YEAR MON DY HF MN SEC LAT N LONG W DEPTH MAG NO GAP DPIIN RPIS EfH ERZ Q 

5~1 1975 APR 20 11 8 47.6 34-29.0 118-51. 1 8.0 2.2 15 131J 13.9 0.12 o.s 0.8 B 

582 24 1 2 26.7 34- 2.9 118-59.5 1. 9 2.0 8 133 2.7 o. 11 1. 2 0.9 B 

58] 25 0 1 25.8 31+- 2.9 118-59.3 16.5 1. 4 9 139 2. 9 o. 12 1 .. 6 1. 2 c 

584 27 13 2 8.6 34- 5.4 119- 0.4 14.3 1.4 8 160 3. 9 0.10 1 .. 1 0.8 c 

585 29 10 25 32.6 34-17.0 119-38.1 11. 6 1. 9 8 86 24.7 o. 20 1 .. 3 1. 9 c 

586 .u y 1 17 53 58.6 34-26.9 119-17.4 14.3 1. 1 8 169 10. 1 0.03 0 .. 3 0.2 B 

587 19 12 51 40.9 34-2 8.4 119- 3.8 12.0 1. 6 9 158 3. 1 0.10 0.9 1. 2 B 

588 26 3 12 16.7 34- 4.7 118-58.8 16.8 1. 5 a qg 1. 8 0.03 o. 4 0.6 8 

5R9 29 5 56 10.6 34-26.8 119-17.5 12.6 1. 2 9 168 9. 9 0.08 0.7 0.6 8 

590 28 12 59 48.8 34- 2.1 118-59.6 12.5 2. 1 14 107 2. 1 o. 14 0.9 0.7 8 

SQ1 JUN 5 1 27 45.6 34-24.2 119-16.4 2.5 1. 7 12 145 7. 5 0.22 1. 1 0.8 c 

5n 5 15 28 29.6 34-25.7 119-52.9 12.3 1. 8 8 89 17.2 o. 06 0.4 0.6 B 

sen 6 13 7 12.4 34-12.1 119-25.4 0.6 1.5 9 113 19.9 0.12 0.8 c 

594 9 16 5 13.8 34- 2 • .1 119- 1.9 1 J. 3 1. 5 10 165 1. 3 o. 17 1. 6 1. 8 c 

I)QS 10 11 43 14.6 34- ().9 118-45.1 8.7 2. 1 11 123 5. 3 0.14 1. 0 1. 1 8 

596 21 20 3 41.9 34- 1.6 119- 1. 1 4. 6 1.9 10 212 1. 1 o. 21 2.0 2.1 c 

597 26 20 36 51. 3 34-15.5 119-32.7 10.6 2. 1 10 87 22.2 o. 15 0.8 1. 3 8 

598 26 20 59 6.4 34-15.9 119-3 2 .l) 14. 3 1. 7 8 130 20.9 0. 06 0.5 0.7 B 

599 JUL 5 12 41 30.5 33-50.2 119-59.8 4.2 1.9 6 234 37.9 o. 12 2.9 D 

600 6 2 19 40.8 34- 3.7 118-53. 1 9.9 2. 3 8 162 17.3 0.16 1. 9 1. 8 c 

601 10 14 7 16. 1 34-1 5.2 119- 36. 8 a. o 2.3 13 8 1 22.8 o. 24 1. 1 2.4 c 

602 12 22 16 22.5 34- 4.6 118-58.5 10.9 1.4 9 132 5. 8 o. 16 1. 3 1. 6 B 

603 13 0 39 42.2 34- 4.4 118-58. 1 11.3 1. 6 10 111 6.0 0.18 1. 4 2.5 B 

604 14 22 15 54.5 34-26.4 118-32.9 o. 1 2.3 14 74 14.6 o. 20 0.8 11. 0 c 

605 15 7 15 36. 3 33-54.5 120-13.6 2. 2 2.0 7 24 1 18.3 o. 17 3.7 3.2 D 

606 16 21 36 30.0 33-52.3 120-14.3 3. 0 2.3 5 255 21. 1 0. 15 5.2 3. 4 D 

607 18 0 41 43.6 34-23.2 119- 33. 1 8.0 1. 7 7 130 19. 1 o. 18 1. 3 7. 1 c 

60A 24 7 2 10.7 33-52.9 118-43.1 5. 1 1.9 16 143 15.8 o. 21 1. 7 3.5 c 

609 24 7 8 24.0 33-51 .9 118-42.6 0.3 1.8 21 133 17.7 0.23 0.9 11.2 c 

610 JO 19 46 38. 1 34-21.6 119-42.8 9.9 2.2 21 92 15.2 0.18 0.8 0.7 8 

611 SEP 2 7 8 38.0 34- 2.8 118-58.4 6.9 1. 4 9 148 4.2 o. 11 1. 1 1. 9 c 

612 24 16 23 3. 3 34-20.1 118-3 2. 2 8.6 1. 7 14 76 B. 2 0.16 0.7 1. 2 B 

613 25 13 36 16.7 33-56.1 118-55.5 13.0 1. 5 9 267 13.4 o. 12 1. 4 3.0 c 

614 26 6 6 34.7 34- 2.q 119- 1. 1 8.0 1.3 8 157 1. 1 0.08 0.8 1. 1 8 

615 OCT 2 22 36 40.3 34-12.9 119- 6.0 8.2 1. 3 10 135 7.6 o. 14 1. 0 2.0 B 

616 3 8 59 17. 1 34-11.7 119- 7.5 5. 2 2. 1 12 95 1 o. 7 0.16 0.9 4.8 c 

617 5 15 10 10.5 34- 2.'l 118-57.1 13.4 2.0 13 15 8 5.4 0.16 1. 3 1. 0 c 

618 9 6 16 56.2 34-23.1 119-41. 1 11. 8 2.6 17 A9 6.5 o. 17 0.8 0.7 8 

619 9 22 39 21. 3 34-15.4 119-45.2 2. 2 1.8 7 87 26.8 0.14 1. 0 c 

62(\ 9 23 42 21. 1 34- 14.9 119-44.2 14.3 1. 9 10 86 27.6 o. 31 1. 9 1. 8 c 

621 9 23 48 17.6 34-15.4 119-45.3 2. 1 1. 8 6 87 26.8 o. 13 1. 2 c 

622 10 7 5Q 52.8 34-14.5 119-32.1 12.2 1. 8 11 145 22.6 o. 17 1. 7 1.7 c 

623 24 14 20 40.9 33-4 8. 3 118-50.8 8.0 1. 8 10 19 6 22.3 o. 16 2. 1 2.4 c 

6:>4 NvV 2 2 27 43.9 34-22.Q 119-18.7 5.6 1. 4 9 138 3. 3 o. 13 0.9 1. 4 B 

625 3 3 42 17.4 33-51.8 118-35.3 16.6 1. 8 12 141 23.9 0. 19 1. 4 1. 0 c 

6?6 o.c;c 25 14 .35 19.3 33-59.5 119- 6.6 8.0 2. 9 16 136 28. 1 o. 20 1. 4 2.0 c 

627 25 14 41 23.5 34- 1. 1 119- 4.5 9.9 2. 1 11 190 10. 2 0.15 1.4 1. 4 c 

628 28 7 5 33.8 34-11 .1 119-53.7 14.8 2.7 7 179 32. 1 o. 15 2.6 2.5 c 

629 28 19 12 24.2 34-21.6 120-20.7 9.5 3. 1 6 255 35.7 0.07 2.2 0.9 c 

630 29 10 35 23. 1 34- 1.9 119- 6.2 1. 8 2. 4 7 16 7 25.5 0.26 2. 6 c 

SB78 1978 AUG 13 22 54 52. 4 34-2 2.1 119-42.9 12.5 4. 9 16 68 4.0 0. 05 0.2 0.4 A 

26 
late Quaternary Deformation in the Western 

Transverse Ranges, California 

By R. F. Yerkes and W. H. K. Lee 

EARTHQUAKE ACTIVITY AND QUATERNARY DEFORMATION OF THE WESTERN 

TRANSVERSE RANGES, CALIFORNIA 

GEOLOGICAL SURVEY CIRCULAR 799-B 

CONTENTS 

Introduction--------------------------------------------------------

Seismicity----------------------------------------------------------

Page 

27 

27 

27 

27 

28 

30 

30 

30 

31 

35 

35 

Map distribution of earthquakes--------------------------------

Depth---------------------------------------------------------

Fault-plane solutions------------------------------------------

Effects of deformation---------------------------------------------

Geodetic evtdence----------------------------------------------

Deformed marine terraces--------------------------------------

Distribution of deformation------------------------------------

Summary and conclusions--------------------------------------------

References cited---------------------------------------------------

ILLUSTRATIONS 

[Plates published separately as U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1032] 

Plate L 

2. 

Figure 1. 

2. 

3. 

4. 

5. 

6. 

Maps showing faults and epicenters of 1970-75 earthquakes and 

location of seismograph stations. 

~'laps showing faults and focal depths of 1970-75 earthquakes and 

focal mechanisms of selected earthquakes. Page 

Index map of part of southern California------------- 28 

Stereoplot of P axes for 51 events, 1970 through 1975---- 29 

Stereoplot of slip vectors for 51 events, 1970 through 

1975------------------------------------------------ 30 

Section along Santa Barbara-Ventura coast showing deformation of dated r.1arine terraces----------------------- 32 

Diagram showing age estima.tes of nollusk collections and 

ash samples from Pleistocene strata in Hall Canyon 

area, near Ventura, and their stratigraphic and 

rnicrofaunal stage correlations--------------------- 33 

Map showing focal mechanisms for the 1973 Point Mugu 

earthquake sequence----------------------------- 34 

TABLES 

Page 

Table 1. Fault-plane solutions geometrically associated with 

specific faults-------------------------------------- 29 

2. Elevations and estimated ages of collections from 

uplifted marine terraces----------------------------- 31 

III 

Late Quaternary Deformation in the Western Transverse Ranges, California 

By R. F. Yerkes and W. H. K. lee 

INTRODUCTION 

The Transverse Ranges are a dcrnina.nt georrorphic-structural province of southern california. Relative to adjoining terrain1 they are 

distinctive not only in their east-west trend, 

but in the type, age, and history of their exposed basement rocks; in the specta<?Ular. rates 

of defo:rmation as indicated by the l.InpOSlllg 

fault-controlled rrountain fronts and extre:nely 

deep basins filled with young, inten~ely d~formed 

deposits; and, perhaps rrost of all, 1n therr long 

resistance to successful palinspastic restoration in the tectonic history of southern cal ifornia. A new and significant phase in interpreting southern california geology was introduced by analyses of the 1971 San Fernando 

earthquake (Wesson and others, 1971; Whitcomb, 

1971; Whitcanb and others, 1973), which verified 

not only the structural dominance but also the 

activity of the several north-dipping reverse 

faults that characterize the Transverse Ranges 

west of the San Andreas fault and bound them on 

the south. 

we report on the seismicity, focal mechanisms, and related aspects of geology as based 

on seismic data recorded during 1970-75 in a 

large part of the western Transverse Ranges. 

The area covered by the present study is shown 

in figure 1; it includes rrost of the Transverse 

Ranges west of the San Gabriel fault and spans 

the Santa Ynez and Anacapa-Santa M:mica faults, 

which fo:rm the northern and southern lx:>'l.D1daries 

of the province. Also shown in figure 1 are the 

epicenters of located historic earthquakes of 

magnitude 6 or greater, all of which were associated with recognized faults. Of these larger 

earthquakes, the five in the western Transverse 

Ranges, especially the 1971 San Fernando and 

1973 Point Mugu, are associated with easttrending north-dipping reverse faults. Fa~tplane solutions for the San Fernando and Polllt 

Mugu earthquakes verify these associations and 

indicate north- to northeast-trending subhorizontal P axes (Wesson and others, 1971; 

Whitcomb, 1971; Ellsw::>rth and others, 1973) • 

SEISMICITY 

MAP DISTRIBUTION 

The epicenters of 630 earthquakes i:J¥-t took 

place in the six-year period 1970 through 1975 

are plotted on plate 11 , as are the surface 

traces of mapped faults. IJJcation quality of 

epicenters, derivation of local magnit·1de! and. 

associated data for the earthquakes ar?. g1ven lll 

Chapter A of this report. 

Ninety-seven percent of the epice,ters are 

located south of the Santa Ynez fault; none are 

obviously associated with the fault. The few 

events north of the fault were not rec-:>rded well 

enough for fault-plane solutions, and none are 

obviously associated with mapped faults. The 

same is true for events northeast of the San 

Gabriel fault. :No att.errpt was made to relocate 

earthquakes of the San Fernando sequen~e, as it 

was extensively studied by t-fuitcarnb, Allen, 

Garmany, and HilerrKll1 (1973). 

Many of the events south of the S::mta Ynez 

fault can be associated geanetrically with specific faults on the basis of focal mec~sms and 

hypocentral depths (table 1). The best associations are made for the Red r-buntain, Pitas PointVentura, Mid-Channel, and Anacapa faults. Stratigraphic and gearorphic evidence indicates that 

all the faults listed have ruptured th~ ground 

surface during late Quaternary time (];1. 1, Ziony 

and others, 1974). The Red r-buntain and Pitas 

Point-Ventura faults have probably rut:tured in 

Holocene time. 

The quality of the associations l::~tween 

earthquakes and specific faults is illustrated 

by tv.x::> examples. A vertical section (figs. 4 and 

5 of Chap. A) shows that projected hYf:'lCenters 

of the 1973 Point Mugu earthquake sequence and 

the projected trace of the Anacapa fault coir_lcide. 

Also, the subsurface trace of the Red r-buntalll 

fault, located independently on the basis of well 

data (R. s. Yeats, written conmun., 1978) , matches 

the distribution of hypocenters. TheE:e and other 

examples support our procedure (table 1) of. 

deriving fault dips on the basis of ge~tr1cal 

associations between surface traces, typocentral 

depths, and focal mechanisms. 

DEPTH 

Within the western Transverse Rarges, the 

deepest hypocenters are 19 km for an e:vent in 

the north-central part of Santa Barbara Channel 

and 17 km for an event in the Oxnard Flain; in 

1 Plates published separately as U.S. Geological 

Survey Miscellaneous Field Studies Map MF-1032. 

27 
EXPLANATION 

-----Major fault- Heavy 

line, historic rupture; 

long dash, inferred; 

short dash, concealed 

11 c;o 

Figure 1.-Part of southern california showing area investigated, and relations of western 

Transverse Ranges (bounded by Santa Ynez, San Gabriel, and Ana.capa-Santa MJnic:l faults) 

to major faults and epicenters of large earthquakes. SB, Santa Barbara; v, Ve'1tura; 

IA, Los Angeles. l'bdified from Jennings and others (1973). 

addition, aftershocks of the 1973 Point Mugu solution quality are "C" or better; the location 

sequence were as deep as 19 km. HcMever, the is known to 5 km or less and the orientation 

depths of earthquakes in the band of seismicity of the nodal planes is known to ± 11° o~ less. 

that extends from the central and northern First-notion data for events cited in table 1 

Santa Barbara Channel to the east center of the are plotted in figure 7 and listed in table 4 of 

map area generally range fran 13 to 16 km. The Chapter A of this report. r."..any of the events 

hypocenters do not delineate any east-west or can be associated geanetrically with ma'?ped 

north-south plunge. faults; the distribution of the fault-plane 

The type and distribution of basarent rocks solutions relative to mapped faults is shown in 

that underlie the Upper Cretaceous and Cenozoic plate 2. All of the solutions along an-1 north 

sed.ilrentary rock sequence of the western Trans- of the Anacapa-Santa Monica fault indicate 

verse Ranges between the Santa M:mica and Santa reverse displacarent and can be associated geoYnez :r.t:>untains are canpletely unknown. Regional- metrically with reverse faults t.L~t sh.a.v geoloscale maps showing inferred structure contours gic evidence of late Quaternary displao~t at 

on the "basanent" rock surface for this area the ground surface, especially the Ra:l MJuntain 

have been published (CUrran and others, 1971, fault, the Pitas Point-Ventura fault (W:tich 

fig. 5; Nagle and Parker, 1971, fig. 13). Can- traverses the city of Ventura), the Mid-Channel 

parison of the contours shown on these maps with fault zone, and the Anacapa fault. 

the focal depths of recorded earthquakes sug- Sare northwest-trending faults sou':"h of the 

gests that the seismicity is generated within Anacapa-Santa MJnica fault are associated with 

the basanent rock sequence or near its surface, fault-plane solutions: two solutions along or 

but no strong correlations in trend or plunge near the San Pedro Escarpment indicate rightare apparent. lateral novement, whereas the 1973 Anacapa 

FAULT-PLANE SOLUTIONS earthquake near Anacapa Island (event 357, pl. 2) 

is best associated geometrically with northeastQuality.--A set of 50 fault-plane solutions 

for earthquakes of lc:x:al magnitude 2 or larger 

was selected fran a total of about 200 on the 

basis of quality of location and solution. For 

rrost of the events tabulated, location and 

dipping reverse m:werrent, perhaps on one of the 

faults mapped along the southwest flank of Santa 

Cruz-catalina Ridge. 

P axes.- The orientations of P axes are 

inferred to be equivalent to the direction of 

28· 
Table 1.--Fault-plane solutions geometrically associated with specific faults 

Depth Apparent 

Fault Category1 Event nurnber2 (km} dip 

Red ~untain3 H 158, 396, 397, 505 5~-11 63° N. 

Pitas Point H, L 8?, 100, 162?, 365, 388, 12-14 60° N. 

391, 618, SB78'? 

Ventura H 40 4-8 60° N. 

San cayetano Q, L 576? 8-16? 60-70° N. 

Mid-Channel Q 41, 51, 90, 449, 482, 558 8-14 65° N. 

Oak Ridge L 129 11 61° s. 

Santa Susana L 428 5?-11 65° N. 

San Pedro p 555, 625 5-11 rv90° 

Anacapa p 197 + 30 aftershocks 8-16 44° N. 

East Santa Cruz Q, p 357? 13-15 38° N. 

basin 

Letter indicates geologic time span of latest known surface movement; 

H, Holocene; L, late Pleistocene; Q, early Pleistocene; P, late Pliocene. 

2 Events are listed in table 4 (chap. A} and plotted on plate 2. SB78 is the 

Santa Barbara earthquake of August 13, 1978. 

3 Subsurface location verified by well data. 

max~ compressive stress for the analyzed 

events (fig. 2}. ~st (82 percent) are within 

15° of horizontal and 60 percent are within 10°. 

The ~maxima, at due north and N. 50° E., 

bracket the approximate nonna.l to the San Andreas fault (at N. 24° E.) as well as the P axis 

for the 1971 San Fernando earthquake. 

Slip vectors.--The distribution, orientation, and classification of slip vectors are 

plotted in figure 3. A daninant max~ shows 

a plunge of about 55° NE., indicating reverseleft-oblique displacement. Subsidiary maxima at 

45° N. and 45° E. indicate north-over-south 

reverse displacement and left-lateral strike 

slip, respectively. The shaded field defined by 

these maxima contains 70 percent of the points. 

This field is dominated by reverse-left-oblique 

slip, which characterized the 1971 San Fernando 

earthquake, arrl north-over-south reverse slip, 

which characterized the 1973 Point Mugu earthquake. As indicated on figure 3 by slip vectors 

for the 1971 San Fernando (SF) and 1973 Point 

Mugu (PM) earthquakes, the displacements for the 

smaller earthquakes in the western Transverse 

Ranges are fully representative of the larger 

events with known displacements. 

Summary.--Fault-plane solutions for events 

in the western Transverse Ranges can be associa ted with segrrents of several east-trending 

north-dipping reverse faults, especially the 

Red ~untain, Pitas Point-Ventura, Mid-channel, 

and Anacapa faults. Geologic evidence indicates 

that these segmmts have ruptured the ground 

surface during late Quaternary time. The soluFigure 2.--stereoplot showing distribution and 

·orientation of P axes for 51 events, 1970-75, 

excluding aftershocks of 1973 Point Mugu sequence. PM, Point ~t.lgu main shock; SF, 1971 

San Fernando main shock (not contourt~}. Contours, 1 percent, 5 percent, and 10 percent 

29 

per 1 percent area; lower hemisphere projection. 

Arrow at N. 24 o E. normal to San And·:-eas fault. 

See table 4, chapter A for data. 
EXPLANATION 

• North-dipping thrust 

0 North-dipping reverse, dip 45° 

• Left-reverse oblique, dip 45° 

6 Reverse-left oblique 

• Right-reverse obltque 

0 Reverse-right oblique 

t South-dipping reverse 

Figure 3.-Stereoplot shaving distribution, orientation, and classification of slip vectors 

for 51 events, 1970 through 1975, excluding 

aftershocks of 1973 Point Mugu sequence. PM, 

Point Mugu main shock; SF, 1971 San Fernando 

main shock (not contoured). Contours 1 percent, 5 percent, 10 percent, and 15 percent 

per 1 percent area; laver hemisphere projection. Shaded area contains 7 0 percent of the 

points. Arrow at N. 24 o E. marks approximate 

normal to San Andreas fault. 

tions indicate near-horizontal P axes oriented 

generally within 30° of normal to the great bend 

of the San Andreas fault. The dominant type of 

displacement indicated by slip vectors varies 

between north-over-south reverse and reverseleft-oblique. These characteristics pertain to 

the entire range of ma.gni tudes recorded within 

the netv.ork area, as well as to larger earthquakes such as the 1971 San Fernando and 1973 

Point Mugu events. 

EFFECTS OF DEFORMATION 

In addition to the praninent topographic 

and geologic effects of the numerous easttrending folds and faults, well illustrated on 

the geologic map of southern Ventura County 

(Weber and others, 1974), unusually high rates 

of deformation across east-trending reverse 

faults of the western Transverse Ranges are evidenced by geodetic leveling, uplift of dated 

marine terrace deposits, and stratigraphic separation of dated strata. 

GEODETIC EVIDENCE 

Comparison of repeated level lines along 

the coast from the Ventura River to the Santa 

Barbara-Ventura County line and norilirar:d along 

the river has confirmed a mintmum average tilt 

up to the north of nearly 13 microradians over 

the period 1920-68 across the Red Mountain-Pitas 

Point-Ventura set of faults (Buchanan-Banks and 

others, 1975); the relative uplift rate is about 

5 m per thousand years. 

Similarly, carparison of 1960 and 1968 level 

surveys shavs that the upper (northern) plate of 

the west-trendirv; Anacapa ("Santa M:mica") 

reverse fault rose by 30-40 mm at least as far 

west as Point Mugu, consistent with continuerl 

thrusting along this frontal system of the Transverse Ranges (Castle and others, 1978). Additional warping between 1968 and 1971 perhaps 

indicates left-lateral reverse creep at depth, 

and 1971-73 (post-1973 earthquake) dat_a indicate 

additional upper-plate uplift of more than 30 mm. 

Regional maps of elevation changes in the 

western Transverse Ranges east of long 119° 15' 

(Ventura) based on comparisons of 1960/61-1968/69 

and 1968/69-1971 (post San Fernando earthquake) 

levelings shaw strong gradient changes associated 

with the Oak Ridge, Santa Rosa, Santa Susana-San 

Fernando-Sierra lf..adre, and Malibu Coaf't (Anacapa?) faults (Castle and others, 1975, figs. 2 

and 5). Of these, only the Santa Rosa fault was 

not associated with recorded seismicity during 

the 1970-75 interval. The data coverage does not 

include the San Cayetano fault, but it does shaw 

that no prominent gradient changes were associated with the Santa Monica and Raynond Hill 

faults east of the shoreline. 

DEFORMED MARINE TERRACES 

At least three deformed marine terraces are 

exposed along the Santa Barbara-Ventura coast at 

elevations ranging from 2 to at least 226 m 

(table 2). The ages of mollusks from deposits on 

the terraces have been estimated by anino-acid 

stereochemistry at 2,500, 45,000, and 80,000 

years (J. F. Wehmiller, written ccmnun., 1978). 

The 45,000-yr terrace is exposed at elevations of 

26 m or less along the seacliff for about 70 km 

west of long 119° near Carpinteria, wl'''2rr'e the 

Red Mountain and associated faults int.ersect the 

shoreline (pl. 1). East of that point. all the 

terraces, including the 2,500-yr terrace, are 

tilted up to the north and east (fig. 4). Apparent average rates of uplift in this area for the 

last 45r000 years exceed 3 m per thou~~ years 

as referred to present sea level, including the 

rate for the 2,500-yr terrace. Rates cf 5 to 6 

m per thousand years are indicated, aqain for 

the youngest terrace, if present-day elevations 

are referred to pre-existing sea levels. Even 

greater rates, up to 9 m per thousand years, 

30 
Table 2.-EZevations and estimated oges of collections from uplifted marine terraces 

Elevation (m) 

Number Collection Shoreline Esti- Uplift rate 

in mated age 4 (m/10 3 yr) 

fig. 4 number 1 Name IDeality angle2 At T ' (10 3 yrs) .Max. Min. 0 

1 M5790 Goleta 5 rvl5 -55 45 1.6 0.3 

2 Y440B carpinteria 26 ru40 -55 (45) 2.1 .9 

3 Y440A Rincon Point 50 N.a. -55 (45) 2.3 1.1 

4 M7245 Punta 146 N.a. -55 45 4.5 3.2 

5 M7229 Punta Gorda 125 N.a. -55 45 4.0 2.8 

6 M7230 Rincon oil 

field 215 N.a. -55 45 6.0 4.8 

7 M7249 Rincon oil 

field 216 N.a. -55 (45) 6.0 5.0 

7a M7283 Rincon oil 

field 262 N.a. -55 45 7.0 5.8 

8 M7273 5 Rincon oil 

field 354 N.a. -55 (45) 9.1 7.8 

9 Y438B Punta Gorda 2 11 0 (2.5) 5.2 5.2 

10 M7228 Culvert 

390.06 6 15 0 2.5 6 6.0 6.0 

11 M7242 Ventura 117 120 -13 80±10 1.7 1.5 

12 Y413B Ventura 15 N.a. -13 80±10 .4 .2 

1 Localities shown on plate 1. 

2 N.a., not available. 

3 T , time of formation; from Bloom and others (1974) . 0 4 Age estimates by sterochemical analysis of :rrollusks by J. F. Wehmiller, University of 

Delaware, Newark, Delaware; estimates in parenth=ses based on map continuity with 

dated sample. 

5 Float of shells and rounded pebbles. 

are suggested by the presence of scattered 

shells and rounded pebbles at ridge tops up to 

354 rn high. 

DISTRIBUTION OF DEFORMATION 

The north-dipping, east-trending Red Mountain fault and associated San Cayetano, Santa 

Susana, Pitas Point-Ventura, and f.tid-channel 

faults coincide in general with an east-trending 

band of seismicity that extends across the 

north half of the area of plate 1. Detailed 

surface and subsurface investigations show that 

very large separations and late Quaternary 

rroverrents have occurred on the Red Mountain 

fault, the Pitas Point-Ventura fault, and segments of the San Cayetano and Santa Susana 

faults. 

Red Mountain fault.--well data fran the 

San Miguelito oilfield area west of the Ventura 

31 

6 Radiocarbon analysis. 

River show that upper Eocene and lower I fiocene 

strata are thrust over Pliocene and Pleistocene 

strata by the Red Mountain fault (R. S. Yeats, 

written camrun.). The age of the young~st 

strata involved in the faulting is not Fell determined on the basis of the well data. HOW'-

ever, the fault truncates a syncline that, east 

of the Ventura River, involves the San Pedro 

Formation as used by weber and others (1973), 

which has been dated at 0. 4 to < 0. 2 million 

years B. P. on the basis of radianetric and stereochemical age estimates (fig. 5) • On the 

assumption that the thrust faulting followed the 

folding, much or all of the 7, 500 rn of separation on the Red Mountain fault could have 

occurred during about the last one-half to one 

million years. 

Pitas Point-Ventura fault.~ere crossed 

by a seismic profile about 2 km offshore in the 

northeastern part of the Santa Barbara Channel, 
1--------West--------+---------------N. 58° W.----------------1 

1---Rincon oil field-----.! .... 

~ 400 8 

300 

EXPLANATION 

--•- Terrace doted 80,000 years 10 KILOMETERS 

--•-- Terrace dated 45,000 years Vertical exaggerahon X 1 0 

--•-- Terrace dated 2,500 years 

-~-Fault-Arrows indicate 

relative movement 

Figure 4.-Section along Santa Barbara-Ventura coast showing deformation of dated marine terraces. 

Numbered localities keyed to table 2. 

the Pitas Point fault appears as a north-dipping 

reverse fault that displaces a late Pleistocene 

erosion surface about 25 m up on the north; it 

appears to cut Holocene strata but not the seafloor (Greene, 1976, p. 508-509; figs. 4, 6). 

Extensive data are available for the Ventura fault (Sarna-Wbjcicki and others, 1976). 

The surface trace is marked by a prominent, 

linear, south-facing scarp as much as 12 m high 

and about 10 km long; it is bounded on the north 

by an uplifted bench. Except where locally 

buried by young surficial deposits, the escarpment forms the boundary between old alluvial 

fan deposits, deformed marine terrace deposits, 

or deformed bedrock, all overlain by old soils 

on the north and young, undeforrred surficial 

deposits overlain by young soils on the south. 

The gradients of all but the largest streams 

that cross the escarpment are deflected upward 

on the north by about 25 m. Test trenches cut 

in surficial deposits across the escarpment 

show numerous small soil-filled cracks that 

camonly are traceable downward into easttrending high-angle faults with separations as 

large as 40 em. The southerly dips of strata 

in the trenches and adjacent boreholes increase 

downward south of the escarprent. The youngest 

strata cut by the fault are apparently Holocene. 

No direct evidence is available as to the 

amount of displacement across the Ventura fault. 

A north-south structure section about 4 km east 

of the Ventura River shows apparent vertical 

separation of about 245 m, up on the north, at 

the base of lower Pleistocene strata (Ogle and 

Hacker, 1969) , although that interpretation is 

based on perrnissi ve evidence. A similar structure section another 5 km to the east, based on 

IIDre closely spaced and abundant data, shows an 

apparent vertical separation of as much as 275 m 

at the base of upper Pleistocene strata. An 

unknown component of left-lateral slip is indicated locally by small folds having nearvertical axes in bedrock just north of the fault, 

and by the fault-plane solution of an associated 

earthquake (no. 40, table 4 of Chap. A). 

San Cayetano fauZt.~parent stratigraphic 

separation across segments of the San Cayetano 

fault diminishes eastward from a maximum of 

7,300-9,000 m (vertical, up on the no~) at 

Sespe Creek (6 km east of long 119°) (Fine, 

1954; Cemen, 1977) , where low scarps in late 

Quaternary stream terrace deposits coincide with 

the fault trace. Ten kilometers east of FillIIDre, late Quaternary alluvium north of the 

Santa Clara River is warped along the buried inferred trace of the fault (Cemen, 1977). Youthful georrorphic features and upthrust Quaternary 

gravel beds at several localities along its 

trace suggest at least late Quaternar:., activity 

at the surface. 

Santa Susana fauZt.--The apparent stratigraphic separation across faults of the Santa 

Susana set is at least 4,000 m, which incJudes 

about 2,000 m vertical offset (up on the north) 

and 3,200 m left-lateral strike slip (Yeats and 

others, 1977). The hanging wall locally is 

expressed topographically; the fault locally cuts 

late Pleistocene fan deposits, and no~easttrending elements along the west margin of San 

Fernando Valley ruptured during the 1971 San 

Fernando earthquake. 

Mid-Channel fault zone.--Published data on 

faults of the Mid-Channel zone are sparse. A 

report by campbell and others (1975) includes an 

interpretive section (B-B 1 ) through tl'~ area of 

Irost intense seismic activity near long 119°45' 

w., lat 34°15' N. The section shows 2 faultbounded gentle anticline ( "12-mile reef") that 

coincides with the .r-ti.d-Channel zone. A medial 

fault cuts upward to the seafloor, but: the southbounding fault is truncated by the Holocene part 

of the undivided Quaternary deposits (unit Q) 

and tre north-bounding fault cuts upw2rd about 

halfway through the lower Pleistocene part of the 

lower Pleistocene and upper Pliocene ~trata (unit 

Qpl). A vertical separation of about 50 m, up on 

the north, at the base of the upper Pliocene 

marine strata (unit Tpu} is shown for the northbounding fault; a separation of simile-":" arrount, 

down on the north, is shown for the scuth-bounding 

fault. No vertical separation is shGV~111 on the 

medial fault. 

A possible correlative of the north bo'lll'l£iary 

fault of the zone (the isolated segmert at long 

119°30' W., lat 34°11' N.) is illustre-ted in a 

seismic profile and interpretive sectjon by 

32 
(/) 

~ 

w 

1--

w 

~ 

z 

v) 

(/) 

w 

z 

~ 

o~--~~~~--~ 

'\ 

500 

1000 

Q) 

0> 

0 

ci5 

c:: 

Q) .Q 

c:: 0 

~ I 

.E Q) 

.5!? a. :_~ 

Q) 

0> 

0 

~ 

San ~e~\M7238 

Pedro 

Formation ~M7240 ~ 

\ 

\ 

of 

Weber and 

others ( 1973) \ 

EXPLANATION 

• M7238 Locality number of 

mollusk collection 

0 P-15 Locality number of 

ash sample 

(See plate 1; tahle 2) 

u 

I 

1--

(/) 

- Santa Barbara ~ 

\ Formation \ c:: 

.Q 

\ I... 

of \ 

t-----(!~---; P- 1 5 

Q) 

Q) 

Weber and others ( 1973) \ 

Q) c Q) Q) 

u .s:::. 

~ 1500 

\ 0 

~ Q) 

a: 

0> 

3: 

0 

--I Pico Formation 

0 0.2 0.4 0.6 0.8 1.0 1.2 

AGE, IN MILLION YEARS BEFORE PRESENT 

Figure 5.~ge estimates of mollusk collections and ash samples from Pleistocene strata in Hall 

Canyon area, near Ventura, and their stratigraphic and microfauna! stage correlations. 

Stratigraphic bot.mdaries of Hallian Stage fran Natland (1952, pl. 7) . Age estimates 

on rrollusks by J. F. Wehmiller; age estimates on ashes based on analyses and co-:-relations by A. t-1. Sarna-wojcicki. 

Greene (1976), fig. 8, "Santa Barbara slope" 

fault). The section indicates about 120m of 

vertical separation, up on the north, and the 

profile suggests that the fault cuts through 

lower Pleistocene deposits (unit Qs) to the seafloor. These interpretations, coupled with the 

gear~etric associations of the focal rrechanisms, 

indicate that the Mid-channel zone is seismically 

active, but whether one fault or rrore is active 

cannot be determined. The fault-plane solutions 

associated with the Mid-Channel zone occur in the 

general area where the Oak Ridge fault, which onshore is known to dip south and to parallel the 

south flank of the Ventura basin syncline, intersects the !·tid-Channel zone. The dip of the midchannel faults is thus not easily evaluated, and 

their association with the fault-plane solutions 

is weak. 

Oak Ridge fault.----Ifue Oak Ridge is a gently 

to steeply south-dipping reverse fault, the sur33 

face trace of which generally follows the south 

bank of the Santa Clara River. At South M:>untain, just west of long 119°, the fault thrusts 

lower Miocene and upper Eocene strata o· 7er late 

Pleistocene strata, for an apparent stratigraphic 

separation of at least 2,000 m (Baddley, 1954). 

Near Saticoy, displacement in late Quaternary 

sediments has caused a ground-water barrier. 

Offshore data from seismic profiles bet"·reen long 

119°15' and 119°30' indicate that Pleistocene 

strata are upthrown on the south more than 135 m; 

no surface displacement at the seafloor is known 

(Greene, 1976). Available data indicate that 

displacement is dominantly reverse (see fig. 7, 

Chap. A, and pl. 2, event 129). 

Anacapa-Santa Monica fault.--The A~acapa and 

Santa M:mica faults are major elements of an 

east-trending zone of deformation that marks the 

southern front of the Transverse Ranges along the 

south flank of the Santa M:>nica and San Gabriel 
1-buntains. Other elements of the zone include 

the Raymond Hill and CU.carronga faults; the zone 

extends east onshore for about 100 km, and all 

faults are north-dipping reverse faults. East of 

its intersection with the shoreline at Santa 

Monica, two or more subparallel elements of the 

zone are recognized. One, generally called Santa 

1-bnica, is alined with a north-dipping reverse 

fault at the mouth of Potrero canyon that cuts 

upper Pleistocene terrace deposits; to the east 

it is associated with topographic scarps in upper 

Pleistocene terrace deposits. Other elements 

locally are associated with a ground-water 

barrier in Pleistocene deposits; in the Santa 

M::mica area, a topographic scarp in upper Pleistocene deposits is alined with the barrier (Hill 

and others, 1977). 

The apparent stratigraphic separation across 

these faults is variable from west to east, 

according to well data. Northward dips of 40° to 

70° and apparent reverse separations of 1,770 to 

2, 133 m at the top of middle Miocene strata are 

reported for the Sawtelle oil field-Beverly Hills 

oil field area (Knapp and others, 1962; Eschner 

and Scribner, 1972; lang and Dressen, 1975) 8-15 

km east of the shoreline at Santa M::>nica. Separations at the surface of the buried basement 

canplex are pcx>r 1 y known, but a published structural contour map based on a density-residual 

gravity model shows vertical separations in the 

range of 2,400-3,660 m (McCulloh, 1960, fig. 

150.1). However, vertical separations at basement may be a relatively small component of displacement across the zone, which is inferred to 

include a large component of left-lateral strike 

slip (Carrpbell and Yerkes, 1976), in part to 

account for juxtaposition of dissimilar basement 

rocks and pre-upper Miocene sequences west of 

the Newport-Inglew:o:i zone. West of the shoreline, the fault zone includes a northern branch, 

the Malibu Coast fault, and a southern, offshore 

branch, the Anacapa fault (pl. 1). The Anacapa 

fault is the southern boundary of Transverse 

Ranges physiography, as defined by the easttrending structures of Point Dume (Junger and 

Wagner, 1977, fig. 4) , whereas the Malibu Coast 

fault is a recognized lx>undary between wholly 

dissimilar rock sequences (campbell and others, 

1966). 

The total vertical separation across the 

Anacapa fault is unknown. Up-to-the-north separations of 1,000 to 2,000 mare indicated by structure contours on the Miocene-Pliocene unconformity, 

and 200 to 600 m on lower Pliocene strata, in the 

area south and soutl1west of Point Dume (Junger and 

Wagner I 1977, fig. 7, profiles c-c I , D-D I) • The 

seismic profiles indicate that Quaternary sediments 

in that area are not cut by the fault. 

The Malibu Coast fault dips north at 30°-

700 and all evidence indicates reverse dip slip; 

it marks the zone of deformation along which the 

Santa 1-bnica Mountains block overrides the lowlying terrain to the south. Stratigraphic separation across the zone is indeterminate, since 

it juxtaposes unlike rock sequences along its 

entire length. 'Ibpographic relief across the 

34 

119'03' 119'00' 118157' 34°06'·r-:-=-----------,---------------=, 

~205 

CALIFORNIA 

..'() 

"9 

C> / 

;('. 

34°03' C> 

\1351 

~27 

~~~~ ~274 ~451 200 

~199 

0 

~326 

1 KILOMETERS .............. ~...._____ _ __, 

34°00''L__ _________ __.__ ________ __, 

Figure 6 .-Focal mechanisms for 1973 Point Mugu 

earthquake (No. 197) and aftershoc1"'S. Numbers 

indicate sequence of events (see table 2, Chap. 

A) . Canpressional quadrants dark, dilatational 

quadrants liqht; lower focal hemis:?here. Bar 

shows orientation of P axis. Diagrams located 

at epicenter of event. IDeation and area of 

map shown on plate 2. 

zone is at least 850 m, but very large leftlateral strike slip (60-90 km) in late middle 

Miocene time has been inferred on regional 

grounds (Carrpbell and Yerkes, 1976). Elements 

of the fault have thrust late Pleist-ocene (about 

105,000 years old) marine terrace deposits more 

than 15 m over upper Miocene strata at one 

locality near Malibu canyon, and deposits of 

similar age are cut by faults in the zone at 

several other localities along its length. 

The fault-plane solution for the 1973 Point 

Mugu earthquake is vrell constrained and indicates 

reverse displacement; one of the nodal planes 

dips about 44° north and is georretrically and 

geologically compatible with the Anacapa fault 

{Ellsworth and others, 1973; Stierme~ a~ Ells~ 

worth, 1976; figs. 4 and 5 in Chap. A of this 

report). 

Although the sorrewhat diverse focal IreChanisms and spatial distribution of tl'e aftershocks 

do not correlate well with the nodal plane of the 

main shock (fig. 6; Stierman and Ellsworth, 1976), 

they do indicate dominantly reverse faulting on 

chiefly north-dipping faults in response to 

northeast-southwest compressive stress, as do 

other earthquakes along the zone. 

A corrp:>site fault-plane solution based on 

five events along but just south of the trend of 

the Santa 1-bnica fault, near the east end of the 
Santa ~nica ~untains about 25 km east of the 

map area, indicates a steeply north-dipping 

fault with predaninant reverse displacem:mt, a 

moderate component of left-lateral strike slip, 

a slip vector plunging about 55° N. 66° E., and 

a P axis plunging about 28° N. 18° E. (Hill and 

others, 1977, pl. 4, fig. 8). This solution is 

consistent with those reported fran this study. 

The segment of the Anacapa-Santa ~nica 

fault between long 118°45' w. and 118°20' W. (15 

km east of the present map area) was relatively 

free of recorded seismicity during the 1970-75 

period, whereas many events were recorded 

throughout the area to the south. 'Ihe latter 

area is OOunded by the northwest-trending San 

Pedro escarpment and Newport-Inglewood zones, 

each of which is characterized by daninantly 

right-lateral strike slip on the basis of geologic or seisnologic evidence or roth (see for 

example Hill and others, 1977, pl. 4, fig. 6; 

Buika and Teng, 1978). Buika and Teng (1978) 

note the same concentration of seismicity (during 

1973-76) along the northwest-trending faults 

south of the Santa Monica fault system and relatively sparse seismicity in the Santa ~nica 

~untains to the north. '!hey view this as evidence that the northwest-trending faults are terminated by the Santa ~nica fault system and that 

the Santa ~nica ~untains are acting as a passive and coherent structural block. They also 

conclude that the Santa ~nica fault system was 

the locus of chiefly north-over-south reverseleft-oblique slip as a result of campressive 

stress oriented northeast-southwest. 

Anacapa earthquake.~e 1973 "Anacapa" 

earthquake and an aftershock (events 357 and 359, 

pl. 2) have epicenters very close to the Anacapa 

fault but are best associated geometrically with 

norilivest-trending faults located on the Santa 

Cruz-Catalina PJ.dge 7 to 12 km soutl'w:st of the 

epicenters. Scire northwest-trerrling folds arrl 

short fault segrrents have been mapped in that 

general area, including a northeast-dipping 

thrust fault, but no satisfactory correlation is 

:kn.avn. 

1978 Santa Barbara earthquake.--The Santa 

Barbara earthquake of August 13, 1978 (event 

SB78, pl. 2) , occurred in the same general area 

as the larger 1925 and 1941 earthquakes; its 

epicenter perhaps was between those of the 

earlier events. 

'Ihe distribution of main-shock and aftershock hypocenters describes a surface striking 

N. 65°-70° w. and dipping north (lee and others, 

1978, figs. 3 and 5). This surface trerrls toward the shoreline at Goleta, where the largest 

accelerations were measured and nost extensive 

damage occurred. 'Ihe fault-plane solution, distribution of aftershocks, and local geology 

indicate reverse slip on a fault dipping 30°-60° 

N. The rupture surface and fault-plane solution 

are not clearly associated with a recognized 

fault but may be associated with the Pitas Point 

or nearby fault (see Chap. A, fig. 2). 

35 

SUMMARY AND CONCLUSIC'NS 

Focal rrechanisms based on sane 200 magnitude 2 to 6 events for the six-year period 1970 

through 1975 in the western Transverse Ranges 

reflect the same stress regime as larger:- earthquakes in the province for which records are 

available: near-horizontal pressure ax~s 

directed generally nonnal to the great 1 '~ of 

the San Andreas fault. The inferred CCJ1l?ressi ve 

stress is expressed chiefly by seismicity and 

reverse displacement along several major zones 

of east-trending reverse faults (Red ~untainSan Cayetano, Pitas Point-Ventura, Mid-Channel, 

and Anacapa-Santa ~nica); same left-lateral 

strike slip also is indicated. This type of 

deformation is entirely typical of that measured 

after the 1971 San Fernando earthquake over an 

area of nore than 250 square kilareters: 

1. 1. 4-m vertical (up on the nortl:) separation across the rupture zone. 

2. 1. 9-m left-lateral separation. 

3. 0. 55-m north-south shortening normal 

to the fault trace. 

4. Differential arching and depression of 

nore than 2 m, which accentuated 

pre-existing landforms. 

5. Horizontal deformation on a regional 

scale that lengthened nortrn resttrending control lines. 

~st significantly, the evidence on rate 

and sense of defonnation is mutually C011sistent 

for individual faults: geologic data on age and 

sense of latest displacem:mt and arrount and 

sense of stratigraphic separation, geod~tic data 

on tilting of coastal areas underlain by faults, 

uplift of dated marine terrace deposits in 

coastal areas under lain by faults, and associa ted focal rrechanisms. The indicated avE>.rage 

rates of vertical defonnation (5-10 m ~r thousand years) have been constant at least over the 

last 45,000 years. 

The east-trending reverse faults tl'~.t doninate the structure of the western Transverse 

Ranges are slip surfaces along which ma11y kilometers of north-south shortening and a lesser 

arrount of east-west extension have occw:-red in 

late Quaternary tine. At the present rates, all 

the measured canpressi ve deformation within the 

western Transverse Ranges could have OC<"!Urred 

during the last 0. 5 to 1 million years. 

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A., Mattllews, R. K., and Mesolella, K. J., 

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37