Expectable Earthquakes and 

Their Ground Motions in the 

Van Norman Reservoirs Area 

By R. L. Wesson, R. A. Page, 

D. M. Boore, and R; F. Yerkes 

THE VAN NORMAN RESERVOIRS AREA, 

NORTHERN SAN FERNANDO VALLEY, CALIFORNIA 

GEOLOGICAL SURVEY CIRCULAR 691-B 

Prepared on behalf of the Federal 

Disaster Assistance Administration 

CONTENTS 

Page 

Albstract ______________________________________________ B1 

Introduction------------------------------------------ 1 

Expectable earthquakes ------------------------------ 1 

San Alndreas fault -------------------------------- 1 

Sierra Madre-San Fernando-Santa Susana 

fault zone -------------------------------------- 2 

Page 

Expectable earthquakes-Continued 

Other fault zones -------------------------------- B4 

Ground motions at the Van Norman sites -------------- 4 

M 8+ earthquake on the San Alndreas fault -------- 4 

Local earthquake -------------------------------- 6 

Summary -------------------------------------------- 7 

References cited -------------------------------------- 9 

ILLUSTRATIONS 

Page 

FIGURE 1. Vertical section through hypocenters of the 1952 Kern County and 1971 San Fernando 

earthquakes ---------------------------------------------------------------------------------- B3 

2. Plot of peak horizontal acceleration versus distance to slipped fault as a function of magnitude ________ 5 

3. Plot showing estimate of response spectrum envelope for Van Norman sites, M 8'h earthquake on 

San Alndreasfault ---------------------------------------------------------------------------- 7 

4. Plot showing estimate ofresponse spectrum envelope for Van Norman sites, local earthquake ofM 7lf2__ 8 

TABLES 

Page 

TABLE 1. Magnitude estimates for an assumed rupture length of 65 km (40 mi) -------------------------------- B3 

2. Earthquakes of M 7 or more associated with shallow onshore reverse-slip and reverse-oblique slip faults__ 4 

3. Expected values of horizontal ground motion for Van Norman sites ---------------------------------- 6 

III 

THE VAN NORMAN RESERVOIRS AREA, 

NORTHERN SAN FERNANDO VALLEY, CALIFORNIA 

Expectable Earthquakes and Their Ground Motions 

in the Van Norman Reservoirs Area 

By R. L. Wesson, R. A. Page, D. M. Boore, and R. F. Yerkes 

ABSTRACT 

The Van Norman reservoirs complex lies immediately upstream from a densely populated area. For this reason, the 

seismic stability of dams proposed for the complex should be 

analyzed on the basis of the worst seismic hazard that can 

reasonably be expected to affect the area. Accelerograms used 

in dynamic analyses to predict the response of the dam structures to earthquake loading should be chosen to (1) model the 

maximum expectable earthquakes from the tectonic province 

in which the dam is located and (2) adequately represent the 

ground motions expected at the damsites from those earthquakes. Two earthquakes are considered: a great earthquake 

in excess of M 8 on the San Andreas fault some 40 km (25 mi) 

northeast of the reservoirs area and a local earthquake of M 

7lh-7% along the Sierra Madre-San Fernando-Santa Susana 

system of faults, within which the reservoirs area is located. 

The geologic and tectonic bases for expecting these earthquakes include an analysis of the seismic and tectonic history 

and environment of the Transverse Ranges of southern 

California. Basic parameters are suggested for the selection of 

accelerograms to model these two earthquakes, including suggested values for the peak horizontal acceleration, velocity, 

dynamic displacement, and duration. 

INTRODUCTION 

The Van Norman reservoirs area is within the 

Transverse Ranges of southern California, a region characterized by intense ongoing tectonic activity, which is responsible for a high level of seismicity and a history of damaging earthquakes. 

Because of the great potential for loss oflife and for 

extensive property damage in the event of failure, 

we believe that the design of proposed dams should 

be analyzed in the light of the severest groundmotions tha't can reasonably be expected from 

earthquakes in the vicinity. In this report we 

analyze the earthquake hazard at the Van Norman site by considering two questions: What 

reasonably expectable earthquakes represent the 

most severe seismic hazard at the sites? What 

ground motions are reasonably expectable at the 

damsites from these earthquakes? 

It is anticipated that proposed dams will be subjected to dynamic analyses in order to predict their 

performance under earthquake loading. Our purpose is to suggest criteria for the selection of accelerograms to be used as input for these analyses. 

EXPECTABLE EARTHQUAKES 

The maximum earthquake to be expected along 

a given fault zone can be predicted on the basis of 

(1) the seismic history of the fault zone, (2) the 

seismic history of the tectonic province, (3) a comparison with the seismic history of other fault 

zones in analogous structural and tectonic circumstances, and (4) magnitude-fault length relations. 

The two fault zones that appear likely to produce 

earthquakes accompanied by severe ground motions in the Van Norman area are (1) the San 

Andreas, some 40 km (25 mi) to the northeast and 

(2) the Sierra Madre-San Fernando-Santa 

Susana, within which the area is located. 

Bl 

SAN ANDREAS FAULT 

A great earthquake (greater than M 8) along the 

segment ofthe San Andreas fault nearest the Van 

Norman area unquestionably must be expected. 

Such an earthquake occurred in 1857, and there is 

every reason to believe that the processes responsible for that earthquake will continue into the 

foreseeable future. The magnitude of the 1857 
event is unknown, but from the length of faulting 

involved, it must have been at least as large as the 

1906 San Francisco earthquake, M 8.3. Therefore, 

an earthquake in excess of M 8 must be anticipated. 

SIERRA MADRE-SAN FERNANDOSANTA SUSANA FAULT ZONE 

Three historic earthquakes in the San Fernando 

area were capable of producing substantial damage: 

1700's (1769?). Magnitude unknown. Bonilla 

(1974) describes evidence that one of the 

scarps resulting from the 1971 San Fernando earthquake is associated with a buried scarp like feature of even greater height 

that was formed about 200 years ago. This 

scarp may have been formed during the 

very large earthquake felt by the Portola 

expedition in 1769. 

1893, Pico Canyon earthquake. About M 6 (C. 

R. Allen in Wentworth and Yerkes, 1971). 

1971, San Fernando earthquake. M 6¥2. 

The magnitudes of all three earthquakes are estimated to be 6 or greater. The inferred major earthquake on the San Fernando fault zone about 200 

years ago was associated with a scarplike feature 

having a height of more than 1m (3.3 ft) (an upper 

bound could. not be determined) in Lopez Canyon, 

6¥2 km (4 mi) east of the reservoir area; this height 

is definitely greater than that of the 1971 fault 

scarp at the same locality (0.9 m, 2.9 ft). Observations of the worldwide record indicate that fault 

displacements generally increase with earthquake magnitude (Bonilla, 1970; Bonilla and 

Buchanan, 1970); on this basis the earthquake 

that occurred about 200 years ago was larger than 

the 1971 earthquake ofM 6¥2 (Bonilla, 1974). Correlations based on the worldwide record indicate 

that the older partial scarp at Lopez Canyon corresponds to an earthquake of at least M 6%, disregarding the distribution of displacement on one or 

more scarps. It is clear from even these limited 

data that the San Fernando earthquake is by no 

means a unique or isolated event, nor was it the 

largest possible. 

The Transverse Ranges of California, in which 

the Van Norman sites are located, are characterized by geologic structure resulting from longestablished north-south compression, accompanied by intense and ongoing tectonic and seismic activity. The earthquakes in the Van Norman 

area, including the 1971 event, occur in response 

B2 

to the same tectonic forces, and in some cases in 

similar geologic circumstances, as other earthquakes in the Transverse Ranges area (see following list); some of them were significantly larger 

than the 1971 event. 

Historic large earthquakes in the western Transverse Ranges 

area on faults other than the San Andreas 1 ({rom Richter, 

1958: Allen, 1971) 

1812 (December 21), Santa Barbara Channel? Magnitude 

unknown but listed as "outstanding." Rossi-Forel intensity 

IX-X in Santa Barbara. 

1852, Big Pine. Magnitude unknown, but may have been associated with surface rupturing. 

1893, "Pico Canyon." About M 6. 

1916, Tejon Pass. About M 6.0. (May have occurred on San 

Andreas fault.) 

1925, Santa Barbara Channel. M 6.3. 

1927, Off Point Arguello. M 7.5. 

1952, Kern County. M 7. 7. Three aftershocks greater than M 6. 

The geologic-tectonic setting of this earthquake is analogous 

to that of the San Fernando earthquake. 

1971, San Fernando. M 61h. Surface rupturing. 

1Earthquakes felt in the vicinity of the Santa Barbara Channel, and therefore 

pertinent to the Transverse Ranges, are described in detail by Hamilton, Yerkes, 

Brown, Buford, and DeNoyer (1969) and Lee and Vedder (1973). 

A particularly apt analogy may be made between the 1971 San Fernando earthquake, south 

of the San Andreas fault, and the 1952 Kern 

County earthquake (M 7.7), north of the San Andreas fault. Both involved substantial reverse-slip 

and left-lateral strike-slip displacement along 

range-front faults that dip toward the San Andreas. Allen (1972), among others, has suggested 

that the stress system responsible for both the 

1952 Kern County earthquake and the 1971 San 

Fernando earthquake is a result of the ~~great 

bend" in the San Andreas fault immediately north 

of the Transverse Ranges. The crustal block 

southwest of the San Andreas fault is moving 

northwestward - parallel to the general trend of 

the fault zone - relative to the crustal block 

northeast of the fault. The San Andreas fault opposite the Transverse Ranges trends more nearly 

westerly. In the area of this ~~great bend," the tectonic forces responsible for the movement of the 

crustal blocks - shearing along the generally 

northwestward-trending San Andreas fault zone 

- are resolved into north-south compression 

across the Transverse Ranges. 

A schematic south-north cross-section offset 

along the San Andreas fault (fig. 1) clearly shows 

the symmetry of the White Wolf and San Fernando 

fault zones and the 1952 Kern County and 1971 

San Fernando earthquakes. Each of these earth-
Section offset 80 km 

along San Andreas fault 

I 

CJ) 

w 

_J 5 

-+ ~ 

I 

t1o 

w 

0 

15 

0 

0 

FIGURE 1.-Vertical section, offset 80 km along the San 

Andreas fault, through the hypocenters of the 1952 Kern 

County and the 1971 San Fernando earthquakes. 

Geologic units marked "TQ" consist of Tertiary and 

Quaternary sedimentary rocks. Symbols "A" and "T" inquakes was generated by a sudden displacement 

-with both left-lateral and reverse components 

-along east-trending faults in response to stresses associated with the San Andreas system. 

The magnitude of an earthquake appears to be 

empirically related also to the length of fault rupture in the earthquake (Bonilla and Buchanan, 

1970). The maximum magnitude of an earthquake 

on a particular fault zone can thus be estimated 

crudely by assuming the maximum fraction of the 

total length that might rupture in a single earthquake. (See Wentworth and others, 1969.) It is 

difficult to apply this technique to the fault zone 

along the south margin of the Santa Susana and 

San Gabriel Ranges because of the complex relations of the faults as well as the complex nature of 

the faulting associated with the earthquakes, as 

demonstrated by the surface ruptures resulting 

from the 1971 San Fernando earthquake. Evidence has been presented for late Quaternary displacement along the south margin of the Santa 

Susana and San Gabriel Ranges, which extend 

from Oak Ridge (northwest of Santa Susana) to 

San Bernardino, a distance of some 130 km (80 mi) 

(Jennings and Strand, 1969; Proctor and others, 

1970; Rogers, 1967; Wentworth and others, 1970; 

Wentworth and Yerkes, 1971). On the basis of 

observed magnitude-fault length relations, the 

5 10 MILES 

5 10 KILOMETERS 

Basement 

I 

I 

I /, Basement 

T/A 

-1952 KERN CO J' M 7.7 

CJ) 

a: 

w 

5 ~ 

:; 

0 

_J 

10 ~ 

z._ 

15 ~ 

20 

CL. 

w 

0 

dicate relative movements "away from" and "toward" the 

reader, respectively. Arrows at left and right margins 

indicate the general direction of lateral compression to 

which the earthquakes are attributed. 

magnitude of the maximum event involving half 

this length,1 or 65 km (40 mi), would be about 7~ 

(table 1). 

TABLE 1.-Magnitude estimates for an assumed rupture length 

of65 km (40 mi) 

Relation between magnitude (MJ and fault length !L, in kilometers) Reference Estimated 

magnitude 

tt::8:~~~~~gLr~!~6~~= ===== === ===== === ====== == ¥~~h~~ ?1~ss)========== = ~ :~ M=2.91 (}og LH2.64 ~-----------------------Bonilla and 7.8 Buchanan (1970l !all North American datal. Graph !lower dashed line in Albee and Smith fig. 1 of reference). <19671. 7.8 

These estimates of magnitude-rupture length 

relations combined with (1) the seismicity of the 

Transverse Ranges, (2) the seismic history of the 

immediate area, (3) an ancient displacement on 

the San Fernando fault zone inferred to be larger 

than that of 1971, (4) the analogy between the 

White Wolf fault zone (1952 Kern County earthquake) and the San Fernando fault zone, and (5) 

magnitude-fault length relations suggest that the 

1971 earthquake (M 6¥2) should not be accepted as 

1This practice, although widely used, has little observational data to support it. 

Wentworth, Ziony, and Buchanan !19691 observed that the "ratio of length of 

rupture to length of the whole fault for about 10 historic North American events 

ranges at least from 0.02 to greater than 0. 75." [n view of this variation, the adopted 

ratio of 0.5 is not particularly conservative. 

B3 
the maximum that can be expected from this tectonic system, especially since this system has already produced one M 7.7 earthquake in this century. On this basis a local earthquake of at least M 

7¥.r 7% is reasonably expectable. 

Great earthquakes associated with reverse-type 

faulting are relatively common along the landward margins of ocean trenches (for example, 

Alaska, 1964, M 8.5; Chile, 1960, M 8.5). Large 

earthquakes also occur on onshore shallow reverse 

faults that are not primary plate boundaries (table 

2). While perhaps less important in terms of plate 

tectonics, these earthquakes are nonetheless large 

enough to have severe consequences. 

TABLE 2.-Earthquakes of M 7 or more associated with shallow 

onshore reverse-slip and reverse-oblique slip faults 

Year 

1929 

1931 

1944 

1945 

1951 

1951 

1952 

1962 

1968 

1968 

[From Bonilla and Buchanan <1970)) 

Length of surface <kml Location Magnitude rupture1 

West Nelson, New Zealand --------------------- 7.8 Hawkes' Bay, New Zealand --------------------- 7.9 San Juan, Argentina --------------------------- 7.8 

~!fl':.ara~f.a,r;i;;~-=========================== ~:~ Yuli fault, Taiwan ----------------------------- 7.3 White Wolf fault, California--------------------- 7.7 

Buyin-Zara, Iran ------------------------------- 7.2 

~:~:t::;: f:~~i~~~-======================= ~:5 

11 

10 .7 

9 

7 

40 

53 

103 

1 

37 

1The surface rupture lengths for several of these earthquakes are anomalously low in relation to their magnitudes (Bonilla and Buchanan, 1970, fig. 3). This may result from the poorly defined surface ruptures of such faults or from difficulties in inves- tigating the individual faults (such as extension offshore). 

OTHER FAULT ZONES 

Other fault zones in southern California, such as 

the Santa Ynez, Newport-Inglewood, and Malibu 

Coast faults, and perhaps even the San Gabriel 

fault, must be considered capable of producing 

earthquakes at least comparable to the one discussed here for the Sierra Madre-San Fernand~ 

Santa Susana zone. In addition, many other faults 

should be considered capable of generating earthquakes as large as the 1971 earthquake (Wentworth and others, 1969). However, given the proximity of the Van Norman area to the Sierra 

Madre-San Fernand~Santa Susana and San Andreas fault zones, it is reasonable to accept the 

maximum expectable earthquakes on these two 

zones as an estimate of the worst seismic hazard 

that might affect the area. 

GROUND MOTIONS AT THE 

VAN NORMAN SITES 

M 8+ EARTHQUAKE ON THE SAN ANDREAS FAULT 

To design a structure that will resist strong 

ground shaking, the expected ground motion must 

be described quantitatively. Strong ground motion 

can be described in terms of peak horizontal acceleration, velocity, displacement, and the duration 

of strong shaking. It would be ideal if there were 

direct observational data upon which to draw, but 

unfortunately no such data have been recorded 

closer than about 100 km (60 mi) to the causative 

fault of an M 8 or larger earthquake. Therefore, 

the ground motions in the Van Norman area from 

a great earthquake on the San Andreas fault, 25 

mi to the northeast, must be modeled by a synthetic accelerogram that is selected or constructed on 

the basis of extrapolating available data and physical arguments, such as theoretical models of the 

earthquake source. The accelerogram should be 

characterized by parameters estimated from the 

best available data on peak horizontal acceleration, velocity, displacement, and duration of 

strong shaking2 as a function of distance from the 

causative fault. Existing observational data, critically reviewed and tabulated by Page, Boore, 

Joyner, and Coulter (1972), clearly indicate that 

for a given distance from the causative fault (for 

example, the distance from the San Andreas fault 

to the Van Norman reservoirs area, indicated by 

the verticalline=40 km or 25 mi) the peak acceleration increases with magnitude (fig. 2). Thus, an 

earthquake in excess ofM 8, at a distance of25 mi, 

probably would produce a peak acceleration of 0.5 

gat the Van Norman site. 

Page, Boore, Joyner, and Coulter, (1972, table 2) 

have estimated the peak horizontal acceleration, 

velocity, and dynamic or transient displacement 

on competent foundation materials near the 

causative fault for an M 8.5 earthquake; these 

values are 1.25 g, 150 em/sec (4.9 ft/sec), and 100 

em (3.3 ft), respectively. The estimated peak velocity and transient displacement at the VanNorman 

sites, 40 km (25 mi) from the fault, are estimated 

at 60 em/sec (2.0 ft/sec) and 40 em (1.3 ft), assuming that they attenuate in the same proportion as 

the peak acceleration (0.5 g /1.25 g). These values 

are compatible with the scanty data available. 

(See Page and others, 1972.) They are given in 

table 3, along with levels of acceleration exceeded 

or attained 2, 5, and 10 times and levels of velocity 

exceeded or attained 2 and 3 times. 

B4 

2Page, Boore, Joyner, and Coulter (1972), comparing near-fault accelerograms 

with the felt reports, concluded that the phase of "intense" or "strong'' shaking 

corresponds to accelerations of 0.05 g or greater. This definition is adopted in this 

report. This measure of duration does not always represent the total interval of time 

over which damage to structures and ground failure may occur (Seed and Wilson, 

1967; McCulloch and Bonilla, 1970). 
0 

1.0 

0.52g 0·5 ,.. •-o::-.~08~km _ _.. 

I 

1 /Suggested value for acceleration if at Van Norman sites for earthquake in excess of M 8 on the 

I San Andreas tau It 

I 

I 

00 I 

0.2 

0.1 

b() 

z 0 0.05 

~ <( 

a: 

w 

...J 

w 

u 

u 

<( 0.02 

0.01 

0.005 

0.002 

EARTHQUAKE 

MAGNITUDE 

• 5.0-5.9 

0 6.0-6.9 

• 7.0-7.9 

~ 

b 

o 10 

o• 

IO 

rt~o 1 : 0 0 

I 

I 

c 

0. 

0 

• 

0 

~0 • 

000 

00 0 

<I> 

0 

• 

•• 

10 20 50 100 200 

DISTANCE (KM) 

FIGURE 2.-Peak horizontal acceleration versus distance 

to slipped fault as a function of magnitude. Except for 

1949 Puget Sound shock (open squares), data shown are 

those for which distances to fault are most accurately 

known. Straight-line segments connect observations at 

different stations for an individual earthquake, for 

three M 5 shocks, and one M 7 shock. From top to 

bottom, suites of M 5 data are from 1970 Lytle Creek 

(M=5.4), Parkfield (M=5.5), and 1957 Daly City 

(M=5.3) shocks. Closest Parkfield data point lies off plot 

to left at 0.08 km. ForM 6, most data within 100 km are 

from 1971 San Fernando earthquake (M=6.6), and most 

data beyond 100 km are from 1968 Borrego Mountain 

earthquake (M=6.5). Most M 7 data are from 1952 Kern 

County shock (M=7.7). Open squares are values from 

1949 Puget Sound event (M=7.1), for which distances 

are determined to hypocenter assuming minimum focal 

depth of 45 km. Arrows denote minimum values. (From 

Page and others, 1972.) 

B5 
Current nonlinear dynamic analyses used in the 

design of structures require a time history of acceleration, an accelerogram, as input. Many accelerograms can be constructed with the parameters specified in table 3, but it is essential that 

accelerograms used in the analyses not be 

deficient in energy at periods that are critical to 

the response of the particular structure. These 

critical periods are not generally known in advance of the analyses, because-if the response of 

the structure is nonlinear-they depend on the 

form and duration of the excitation. 

It is necessary, therefore, to evaluate the frequency content of candidate accelerograms. To do 

this, a response spectrum envelope (fig. 3) was 

prepared, using the parameters specified in table 

3. This envelope can be compared with the response spectrum calculated from a candidate accelerogram. We introduce the response spectrum 

envelope as a method of determining whether or 

not candidate accelerograms have sufficient 

energy throughout the range of periods potentially 

critical to the particular structures. We do not 

propose that the response spectrum envelope replace dynamic analysis as a design tool. If only one 

accelerogram is used in the dynamic analysis, its 

spectrum should contain sufficient energy over the 

entire range of critical periods and have no 

significant excursions below the envelope. A suite 

of model accelerograms could also be used, which 

together would test the structure throughout the 

range of potentially critical periods. 

LOCAL EARTHQUAKE 

As discussed previously, an earthquake greater 

than M 7~ can reasonably be expected in the immediate Van Norman area. Criteria for selecting 

an accelerogram to model the ground motions from 

this local earthquake are derived as in the preceding section and are given in table 3. Peak horizontal acceleration, velocity, displacement, and duration of strong shaking on competent foundation 

materials within 5 km (3 mi) of the fault causing 

an M 7.5 earthquake are estimated to be 1.15 g, 

135 em/sec (4.43 ft/sec), 70 em (2.30 ft), and 40 sec, 

respectively (Page and others, 1972, table 2). 

These values for acceleration, velocity, and duration are higher than those obtained from the record of the 1971 earthquake (M 6~) at a seismoscope on the sedimentary bedrock that forms the 

east abutment of lower Van Norman dam (Scott, 

1973). 

Again, the frequency content of candidate accelerograms can be evaluated by means of an estimated response ·spectrum envelope (fig. 4), prepared using the values just given. Comparison of 

the estimated envelope with the response spectrum calculated for the Scott accelerogram indicates that the spectrum of the Scott accelerogram 

approaches the envelope for natural periods between about 1.5 and 7 sec (with only minor nholes") 

but that it falls substantially below the expectable 

local earthquake envelope for periods less than 

about 1.5 sec, particularly in the range 0.2--1.5 sec. 

One critical difference between the suggested 

parameters for the expectable local earthquake 

(greater than M 7~) and the accelerograms recorded during the 1971 earthquake is duration. 

Although it does not enter directly into the response spectrum, duration is a controlling factor in 

the number of stress cycles a structure experiences. Accelerograms used to model a local earthquake ofM 71h or greater must therefore have an 

adequate duration of strong shaking (greater than 

0.05 g), at least 40 sec. 

TABLE 3.--Expected values of horizontal ground motion for Van Norman sites 

Acceleration, peak absolute values1 

(g) 

Velocity, peak absolute values (em/sec) 

1st 2d 5th lOth 1st 2d 3d 

M 8+ earthquake on 

San Andreas fault 3, 4 -------------------------------------------------- 0.5 0.46 0.4 0.3 60 52 44 

M 7~ local 

earthquake3 ------------------------------------------------------------- 1.15 1.00 .85 .65 135 115 100 

Dynamic 

displacement Duration2 

(em> (sec) 

40 

70 

70-80 

40 

1Maximum absolute value and levels of absolute value exceeded or attained 2, 5, and 10 times for acceleration and 2 and 3 times for velocity. 2Time interval between first and last peaks of acceleration equal to or greater than 0.05 g. 3Values obtained from Page, Boore, Joyner, and Coulter (1972). These values are for a single horizontal component of motion within 5 km of the fault and for sites at which ground motion is not strongly altered by extreme contrasts in the elastic or inelastic properties within the local geologic section or by the pres· ence of. structure~; they contain no factor relating to the nature or importance of the structure being designed. In addition, these values are for competent foundatton matenals. If it can be demonstrated that the foundation materials at the site cannot transmit these motions, the values should be appropriately modified. 4Values are multiplied by a distance attenuation factor of 0.4 (except for duration, which attenuates Jess rapidly with distance). 

B6 
0 

2 

0 

u 

w 

CJ) 

a: 

w 1.00 Q.. 

Iw 

w 

LL 

2 

>-' 

Iu 

0 

..J 

w 

> 

w 

> 

i= 

<( 

..J 

w 0.10 

a: 

0 

0 

::> 

w 

CJ) 

Q.. 

0.01~----~---L--L-~~~~----~--~--~~~~~----~~--~~~~~~ 

0.01 0.10 1.00 10.0 

UNDAMPED NATURAL PERIOD, IN SECONDS 

FIGURE 3.-Estimate of response spectrum envelope (5 percent damping). for Van Norman sites, M 8¥2 earthquake on San 

Andreas fault; technique of Newmark and Hall (1969). (See Page and others, 1972, p. 15, for general discussion of 

response spectra and their derivation and Housner, 1970, for mathematical treatment.) 

SUMMARY 

The following values for peak horizontal acceleration, velocity, dynamic displacement, and duration are reasonably expectable effects, on competent foundation materials at the Van Norman 

sites, during an earthquake larger than M 8 along 

that segment of the San Andreas fault nearest the 

site: 0.5g, 60 em/sec (2.0 ft/sec), 40 em (1.3 ft), and 

70--80 sec, respectively. (See table 3.) 

As regards a local earthquake, a tectonic system 

that has already produced one M 7.7 earthquake 

during historic time (1952 Kern County) must be 

considered capable of producing another; the 

Santa Susana-San Fernando-Sierra Madre fault 

zone, which forms the mountain front in the San 

Fernando area, is a probable locus for such an 

event, as indicated by the ancient large displacement in Lopez Canyon. Reasonably expectable 

B7 
0 

~ u 

w 

en 

a: 

w 

c.. 

1-

w 

w 

u. 

z 

>-' 

1-

u 

0 

....J 

w 

> 

w 

> 

~ <( 

....J 

w 0.10 a: 

0 

0 

:::> 

w 

en 

c.. 

0.01~----~--~--~~~~~------A---~~~~~~~----~~~~~-L~~~ 

0.01 0.10 1.00 10.0 

UNDAMPED NATURAL PERIOD, IN SECONDS 

FIGURE 4.-Estimate of response spectrum envelope (5 percent 

damping) for Van Norman sites, local earthquake of M 71/z; 

technique of Newmark and Hall (1969). Response spectrum 

of record obtained by Scott (1973) from seismoscope on east 

abutment of Lower Van Norman dam from the 1971 San 

ground motions during such a local earthquake 

are characterized by peak horizontal acceleration, 

velocity, dynamic displacement, and duration at 

least as large as the following: 1.15 g, 135 em/sec 

(4.43 ft/sec), 70 em (2.3 ft), and 40 sec, respectively. 

(See table 3.) 

Vertical ground motions also should be considered in the analyses, and accelerograms having 

Fernando earthquake, also shown. (See Page and others, 

1972, p. 15, for a general discussion of response spectra and 

their derivation and Housner, 1970, for mathematical 

treatment.) 

peak accelerations of at least two-thirds the peak 

horizontal values should be used for this purpose. 

The response spectrum for an individual accelerogram might have ~~holes" at natural periods 

critical for the response of a particular structure, 

even though its peak values approach the desired 

envelope. Dynamic analyses should therefore be 

performed with a suite of accelerograms that have 

BB 
the same basic parameters but differ in detail, so 

that no period critical to the performance of the 

structure would go untested. If only one accelerogram is used to model each earthquake, then its 

spectrum should not show significant excursions 

below the estimated envelope. 

REFERENCES CITED 

Albee, A. L., and Smith, J. L., 1967, Geologic criteria for nuclear power plant location: Soc. Mining Engineers Trans., 

v. 238, p. 430-434. 

Allen, C. R., 1971, Seismological environment, in Wentworth, 

C. M., and Yerkes, R. F., Geologic setting and activity of 

faults in the San Fernando area, California, in The San 

Fernando, California, earthquake of February 9, 1971: 

U.S. Geol. Survey Prof. Paper 733, p. 7, 10. 

--1972, Geological and seismological lessons, in Gates, G. 

0., ed., The San Fernando earthquake of February 9, 1971 

and public policy: Special Subcommittee of the Joint 

Committee on Seismic Safety, California Legislature, July 

1972, p. 1-11. 

Bonilla, M. G., 1970, Surface faulting and related effects, in 

Wiegel, R. L., ed., Earthquake engineering: Englewood 

Cliffs, N.J., Prentice-Hall, Inc., p. 47-74. 

--1974, Trench exposures of parts ofthe February 9, 1971, 

surface faults in the San Fernando fault zone, in Geological 

and Geophysical Studies, v. 3 of San Fernando, California, 

earthquake of Feb. 9, 1971: U.S. Dept. ofCommerce-Natl. 

Oceanog. and Atmospheric Adm. (in press). 

Bonilla, M. G., and Buchanan, J. M., 1970, Interim report on 

worldwide historic surface faulting: U.S. Geol. Survey 

open-file report, 32 p. 

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, in Geology, petroleum development, and seismicity of the Santa Barbara Channel 

region, California: U.S. Geol. Survey Prof. Paper 679-D, p. 

47-68. 

Housner, G. W., 1970, Strong ground motion, in Wiegel, R. L., 

ed., Earthquake engineering: Englewood Cliffs, N.J., 

Prentice-Hall, p. 75-91. 

Iida, Kumizi, 1965, Earthquake magnitude, earthquake fault 

and source dimensions: Nagoya Univ., Jour. Earth Sci., v. 

13, no. 2, p. 115-132. 

California, Los Angeles sheet: California Div. Mines and 

Geology, scale 1:250,000. 

Lee, W. H. K., and Vedder, J. G., 1973, Recent earthquake 

activity in the Santa Barbara Channel region: Seismol. 

Soc. America Bull., v. 63, no. 5, p. 1637-1661. 

McCulloch, D. S., and Bonilla, M.G., 1970, Effects ofthe earthquake of March 27, 1964 on the Alaska Railroad: U.S. Geol. 

Survey Prof. Paper 545-D, 161 p. 

Newmark, N. M., and Hall, W. J., 1969, Seismic design criteria 

for nuclear reactor facilities: World Conf. on Earthquake 

Eng., 4th, Santiago de Chile, 1969, Proc., v. 2, p. 

B4-37-B4-50. 

Page, R. A., Boore, D. M., Joyner, W. B., and Coulter, H. W., 

1972, Ground motion values for use in the seismic design of 

the trans-Alaska pipeline system: U.S. Geol. Survey Circ. 

672, 23 p. 

Proctor, R. J., Payne, C. M., and Kalin, D. C., 1970, Crossing the 

Sierra Madre fault zone in the Glendora tunnel, San Gabriel Mountains, California: Eng. Geology-Internat. Jour., 

v. 4-1, p. 1-63. 

Richter, C. F., 1958, Elementary seismology: San Francisco, W. 

H. Freeman, 768 p. 

Rogers, T. H., 1967, Geologic map of California, San Bernardino sheet: California Div. Mines and Geology, scale 

1:250,000. 

Scott, R. F., 1973, The calculation of horizontal accelerations 

from seismoscope records: Seismol. Soc. America Bull., v. 

63,no. 5,p. 1637-1661. 

Seed, H. B. and Wilson, S. D., 1967, The Turnagain Heights 

landslide, Anchorage, Alaska: Am. Soc. Civil Engineers 

Proc., Jour. Soil Mechanics and Found. Div., v. 93 (SM4), p. 

325-353. 

Tocher, Donald, 1958, Earthquake energy and ground breakage: Seismol. Soc. America Bull., v. 48, no. 2, p. 147-153. 

Wentworth, C. M., Bonilla, M. G., and Buchanan, J. M., 1969, 

Seismic environment of the Burro flats site, Ventura 

County, California: U.S. Geol. Survey open-file report, 42 

p. [1973]. 

Wentworth, C. M., and Yerkes, R. F., 1971, Geologic setting 

and activity offaults in the San Fernando area, California, 

in The San Fernando, California, earthquake of February 

9, 1971: U.S. Geol. Survey Prof. Paper 733, p. 6-18. 

Jennings, C. W., and Strand, R. G., 1969, Geologic map of 

Wentworth, C. M., Ziony, J. I., and Buchanan, J. M., 1970, 

Preliminary geologic environmental map of the greater 

Los Angeles area, California-TID-25363: U.S. Atomic 

Energy Comm., Springfield, Va., Clearinghouse Federal 

Sci. and Tech. Inf., 41 p., map scale 1:250,000. 

'': GPO 792.140 B9