From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Subject: N. CA, USA, and World Quake Report 8/13-19/92
Organization: Stanford Univ. Earth Sciences
Date: Fri, 21 Aug 1992 03:04:41 GMT

DISCLAIMER -- THIS IS NOT AN EARTHQUAKE PREDICTION OR WARNING!
  The commentary provided with these map(s) is for INFORMATIONAL
USE ONLY, and SHOULD NOT be construed as an earthquake prediction,
warning, or advisory.  Responsibility for such warnings rests with
the Office of Emergency Services of the State of California.
PLEASE REMEMBER -- THIS IS PRELIMINARY DATA
  Releasing these summaries on a timely basis requires that the
data, analysis, and interpretations presented are PRELIMINARY. Of
necessity they can only reflect the views of the seismologists who
prepared them, and DO NOT carry the endorsement of the U.S.G.S.
Thus while every effort is made to ensure that the information is
accurate, nothing contained in this report is to be construed as
and earthquake prediction, warning, advisory, or official policy
statement of any kind, of the U.S. Geological Survey, or the
U.S. Government.
FOR QUESTIONS CONCERNING THIS REPORT
  Send e-mail to andy@pangea.stanford.edu


Seismicity Report for Northern California,
the Nation, and the World for the week of
   August 13 - 19, 1992

Data and text prepared by
  Steve Walter, Barry Hirshorn, Nan Macgregor Scott, and Allan Lindh
U.S. Geological Survey
345 Middlefield Rd.  MS-977, Menlo Park, CA  94025
Graphics by Quentin Lindh

San Francisco Bay Area   
   
    For the 7-day period ending at midnight on Wednesday, August 19, 1992
the U.S. Geological Survey office in Menlo Park recorded 17 earthquakes of
magnitude one (M1) and greater within the San Francisco Bay area shown in
Figure 1.  Five of these were as large as M2.0, all but one occurring as
part of the Fairfield activity discussed below.  The weekly total compares
with 15 earthquakes recorded during the previous 7-day period, only two of
which were as large as M2.0. 
   A small cluster of earthquakes beneath the central Sacramento delta
Wednesday evening produced the only notable seismicity in the Bay Area (#2
in Fig. 1).  The activity consisted of three M2 and one M3.0 earthquakes
that all occurred within a 90 minute period on Wednesday evening. 
Epicenters located about 10 miles southeast of Fairfield near the eastern
reaches of the Montezuma Slough.  Focal depths ranged from 16 to 20 km,
depths that would be unusually deep on most faults in the Bay Area but
that are common here in the Suisun Bay area where earthquakes as deep as
25 km are not unknown.  The earthquakes are presumed to have occurred
along the Antioch fault.  The seismicity catalog shows numerous M2 events
and occasional M3 events in this area during the past 25 years, most
recently a M2.1 event in late February of this year.  
    Aside from the Fairfield earthquakes, the Bay Area was very quiet
during the week.  There were only a few scattered earthquakes larger than
M1 on the Calaveras fault.  Activity was similar on the San Andreas
except for a M2.7 quake last Thursday on the creeping segment about 2
miles west-southwest of San Juan Bautista (#1/1).  Two M1 earthquakes
occurred early Monday morning at the northern end of the Black Mountain
thrust fault, about 6 miles south of Menlo Park.

Northern California
    
    Seismicity was reduced throughout much of northern California during
the past week with the exception of the Cape Mendocino area where two
separate areas were active.  The first of these active areas was along the
Mendocino fracture zone itself, about 12 miles west-northwest of Petrolia
(#1/2).  This corresponds to the aftershock zone of the M7.1 earthquake
that struck this area in late June and that has been active since.  The
second area, about 12 miles north of Petrolia, became briefly active early
Monday afternoon with four M3 earthquakes occurring in a 50-minute period
followed by six M2 earthquakes over the rest of the afternoon and evening
(#4/2).  The same area produced a trio of M3 events on July 23-24.
    
    Activity was also reduced along the eastern edge of the Sierra Nevada
where the only notable activity was a pair of M2 events east and
southeast of Markleeville (#2/2).  In the northern Owens Valley, a pair of
earthquakes occurred just southeast of Bishop on Monday evening, the
largest a M3.8 event (#5/2).  
    Central California was also quiet with no earthquakes as large as M2
observed along the San Andreas system south of the Bay Area.  The only
earthquakes as large as M2 in the area were a pair of M2 events along the
Big Sur coast north of San Simeon (#3/2).

Long Valley Caldera
        
    It was also a quiet week within the caldera with only two earthquakes
as large as M1.5; both were located at the west end of the south moat
zone, just southeast of Mammoth Lakes.  Three M2 earthquakes occurred
south of the caldera, in the Sierra Nevada terrane. The first of these was
a M2.5 early Saturday morning one mile northeast of Red & White Mountain
(#1/3).  Just before noon the next day a M2.3 event occurred in the
Mammoth Pass area, just south of Horseshoe Lake (#2/3).  Tuesday evening a
M2.0 event occurred directly beneath Mount Morrison (#3/3).        
     

USA Seismicity
    
    According to information provided by the National Earthquake
Information Service (NEIS), no notable earthquakes occurred in the lower
48 states outside of California.  Most of the California events were
aftershocks to the M7.5 Landers quake, the largest a M4.7 event that was
felt at Riverside, San Bernardino, and in the Big Bear area (#2/4).  This
aftershock was felt throughout much of the Los Angeles area and in San
Diego.  It produced rockslides in the Big Bear area.  Two other
aftershocks were as large as M4.  
    Last Friday afternoon a M3.8 earthquake occurred in the China Lake
area, north of the Garlock fault (#1/4).  It was felt at Ridgecrest.
     
The Planet Earth

    On Wednesday a large earthquake struck the Susamyrtau Mountains in the
western Tien Shan Range of central Asia (#6/5).   At least 42 people have
been reported killed or missing so far.  Several villages and at least
7,000 dwellings were destroyed by the earthquake that produced structural
damage to buildings in Bishkek, Kyrgyzstan and was felt in Uzbekistan,
Kazakhstan, and eastern Turkestan.  At least three M6 aftershocks had been
recorded in the first two hours following the Ms7.5 mainshock.
    Other notable earthquakes include a Mb5.7 event beneath the central
Indian Ocean southeast of Sri Lanka (#3/5), a pair of Mb5.9 earthquakes in
the vicinity of the New Britain trench east of Papua New Guinea (#1/5),
and a Mb6.1 earthquake in the Andreanof Islands of the Aleutian chain that
was felt at Adak and on Atka (#5/5).  A number of earthquakes also
occurred along the western margin of Central and South America, including
a Mb5.6 in Colombia that produced some damage in the Manizales area
(#2/5) and a Mb5.3 along the Chile-Bolivia border that was felt at Arica
and Iquique, Chile (#4/5).

Table 1.  Central California Seismicity (M>2.0)

--ORIGIN TIME (UT)-- -LAT N-- --LON W-- DEPTH  N N RMS ERH ERZ       DUR
YR MON DA HRMN  SEC  DEG MIN  DEG  MIN    KM  RD S SEC  KM  KM REMKS MAG

92 AUG 13  732  0.08 40 23.52 124 31.43 15.12  9   .05 1.9  .7 MEN   2.6
92 AUG 13 1156 38.56 40 20.89 124 34.22 25.70 10 1 .11 2.0 1.2 MEN   2.7
92 AUG 13 1737 32.26 40 17.53 125 11.46  4.99 15   .3012.815.8 MEN-  2.1
92 AUG 13 2158 10.92 36 50.22 121 34.55  7.58 83 5 .18  .2  .4 SJB   2.8
92 AUG 14  630 37.39 40 18.04 124 21.36  8.50 18 1 .12  .4  .3 MEN   1.9
92 AUG 14  853 23.68 40 20.59 125  9.72 23.79 14 1 .12 2.112.0 MEN - 2.3
92 AUG 14 1031 45.86 40 24.64 124 28.08 10.23 20 2 .11  .8  .3 MEN   2.4
92 AUG 14 2044 56.54 38 31.39 119 30.53  5.15 10 3 .21 3.113.4 WAK - 2.5
92 AUG 14 2158 19.71 38 50.20 122 23.67  0.90  7   .17  .8 2.9 GVL   2.7
92 AUG 15 1150 18.17 37 29.22 118 50.86 10.12 26   .11  .4 1.5 MOR   2.5

92 AUG 15 2225 53.87 40 20.33 124 31.37 22.59 11 1 .11 1.2  .7 MEN   1.8
92 AUG 16  717 53.07 40 22.24 124 35.35 29.44 18 1 .13 1.4  .8 MEN   2.4
92 AUG 16  837 47.68 40 37.58 124 24.65  5.96 15 1 .10  .9  .9 EUR   2.2
92 AUG 16 1824 39.94 37 36.23 119  1.31  2.37 15   .07  .4  .8 MAM   2.3
92 AUG 17  753 14.72 39 28.23 122 55.93 13.00 27 1 .11  .2  .5 BAR   1.9
92 AUG 17  848 10.28 35 50.73 121  6.87  7.71 52   .24  .4 1.2 SSM   2.6
92 AUG 17 1122 41.72 40 22.23 124 18.54 10.23 22 1 .12  .3  .2 MEN   2.6
92 AUG 17 1514 13.89 38 41.61 119 38.27  0.10 19 1 .14 1.1 1.6 WAK * 2.4
92 AUG 17 2004  6.07 40 30.32 124 17.29  5.20 23 2 .13  .3  .4 EUR   2.9
92 AUG 17 2024 35.34 40 30.53 124 17.35  3.63 19   .12  .5  .7 EUR   3.4

92 AUG 17 2025 35.42 40 30.47 124 17.03  4.50 22 1 .12  .3  .4 EUR   3.3
92 AUG 17 2052 34.28 40 30.27 124 17.08  4.49 23 2 .12  .3  .4 EUR   3.4
92 AUG 17 2054  6.01 40 30.28 124 17.20  5.12 20 1 .10  .3  .5 EUR   2.5
92 AUG 17 2106 58.80 40  8.54 123 49.93 20.63 29 1 .21  .4  .4 MEN   2.1
92 AUG 17 2113  6.32 40 30.35 124 17.34  5.59 22 1 .11  .3  .4 EUR   2.4
92 AUG 17 2116 22.17 40 30.10 124 17.20  4.89 18 1 .11  .3  .6 EUR   2.2
92 AUG 17 2143  6.94 40 30.43 124 17.08  5.17 16 1 .10  .3  .5 EUR   2.0
92 AUG 17 2157 43.90 40 18.78 124 30.31 26.33 14 1 .13 1.6 1.1 MEN   2.3
92 AUG 17 2222 36.84 40 30.59 124 17.34  5.44 21 1 .12  .3  .4 EUR   2.6
92 AUG 18  115 52.63 40 30.37 124 17.32  4.94 22 1 .12  .3  .4 EUR   2.7

92 AUG 18  119 59.50 40 18.51 124 29.64  8.47 20 1 .12  .9  .4 MEN   3.3
92 AUG 18  122 49.61 40 18.39 124 29.85  8.66 14 1 .09 1.1  .5 MEN   2.1
92 AUG 18  237 50.20 37 20.35 118 22.95 12.64 33 1 .07  .3  .9 OWV   3.2
92 AUG 18  238 28.98 37 20.32 118 22.83 12.50 32 1 .07  .4 1.0 OWV-  3.7
92 AUG 18  511  4.40 40 30.64 124 43.07 23.18 13 1 .11 1.7 1.2 EUR-  2.0
92 AUG 18 2119  3.44 38 47.05 122 43.24  3.10 43 2 .14  .2  .6 GEY   2.8
92 AUG 19  129  2.93 37 33.74 118 51.51 10.47 10   .08  .5 1.0 MOR   2.0
92 AUG 19  342 14.96 35 45.72 121 16.18  0.97 53 1 .12  .4 1.4 SSM   2.3
92 AUG 19 1003  5.96 35 43.48 118  1.92 13.12 13 2 .09  .4 1.0 WWF   2.3
92 AUG 19 1212 31.30 38 45.26 122 42.73  2.64 37 1 .13  .2  .5 GEY   2.9

92 AUG 19 1254  1.28 40 23.37 124 14.48 11.03 23 1 .10  .2  .2 MEN   2.8
92 AUG 20  219 14.45 38  8.58 121 54.99 19.78 20   .20  .6  .6 JQN   2.2
92 AUG 20  231  6.73 38  7.89 121 56.16 15.78 72   .27  .4  .6 GRN   3.0
92 AUG 20  238 58.70 38 48.57 122 49.28  0.91 10   .16  .5 1.0 GEY   2.3
92 AUG 20  335 47.28 38  8.26 121 54.87 19.86 19   .26 1.0  .5 JQN   2.0
92 AUG 20  352 27.16 38  8.14 121 55.15 20.40 26   .23  .8  .6 JQN   2.1
92 AUG 20  555 28.88 38 49.85 122 47.82  2.90 14   .04  .3  .7 GEY   2.1

Notes: Origin time in the list is in GMT, in the text and on maps
       it is in local time.
       N RD: is the number of readings used to locate the event.
       N S: is the number of S waves in N RD.
       RMS SEC: is the root mean squared residual misfit for the
                location is seconds, the lower the better, over 0.3
                to 0.5 seconds is getting bad, but this is machine,
                not hand timed, data.
       ERH: is the estimated horizontal error in kilometers.
       ERZ: is the estimated vertical error in kilometers.
       N FM: is the number of readings used to compute the magnitude.
       REMKS: obtuse region codes that denote the velocity model
              used to locate the event.
       DUR MAG: is the magnitude as determined from the duration of
                the seismograms, not the amplitude.  Sort of like
                going to echo canyon and measuring how loud your
                yell is by counting echos.
       FIG: denotes the figure/event number in the maps posted separately.

TABLE 2.
Data from National Earthquake Information Center (NEIC)

UTC TIME    LAT     LONG    DEP GS MAGS  SD STA  REGION AND COMMENTS
HRMNSEC                         MB  Msz     USED

AUG 13
082748.0  61.481N 149.781W  33N         0.9  12 SOUTHERN ALASKA. ML 3.0 (PMR).
084111.3? 11.20 N  87.29 W  33N 4.7     1.0  34 NEAR COAST OF NICARAGUA
153405.8* 53.623N 165.793W  46* 4.7     1.5  29 FOX ISLANDS, ALEUTIAN ISLANDS
204259.9   6.208S 148.904E  46D 5.9 6.0 1.1  62 NEW BRITAIN REGION, P.N.G.
AUG 14
014312.6* 32.657N 141.158E  33N 4.9     0.9  36 SOUTH OF HONSHU, JAPAN
144343.4  34.118N 116.398W   5G         0.7  16 SOUTHERN CALIFORNIA. MD 3.7
162010.4* 17.081S 174.576W 112D 4.9     0.8  27 TONGA ISLANDS
172624.0  24.050N 121.693E  33N 4.9     1.2  28 TAIWAN
200915.8? 29.93 S  65.46 W 300G 4.9     0.6  35 SANTIAGO DEL ESTERO PROV., ARG.
232755.9  35.745N 117.617W   5G         1.0  18 CENTRAL CALIFORNIA. MD 3.8
AUG 15
082414.3  34.070N 116.458W   5G 4.4     0.7  24 SOUTHERN CALIFORNIA. ML 4.5
190212.8   5.160N  75.764W 150G 5.6     0.6  77 COLOMBIA. Mo=1.3*10**18 Nm
        (PPT). Some damage reported in the Manizales area. Felt at Buenaventura,
        Cali, Manizales, Medellin, Pereira, Popayan and Tulua.
213014.4  18.566N 145.600E 193D 4.9     0.9  62 MARIANA ISLANDS
AUG 16
025132.4  59.759N 151.471W  70?         0.8  14 KENAI PENINSULA, ALASKA. Felt
                                                (III) at Homer.
063057.6  34.050N 116.661W   5G         0.7  15 SOUTHERN CALIFORNIA. MD 3.6
102333.8*  5.036S 147.087E 235D 5.9     1.0  48 EASTERN NEW GUINEA REG., P.N.G.
102946.3  44.355N  11.516E  10G         1.1  18 NORTHERN ITALY. MD 3.3 (ROM). ML
144908.1   3.083S  84.980E  33N 5.7 4.9 0.7  38 SOUTH INDIAN OCEAN
201640.5* 30.199N  91.931E  33N 5.0 4.5 1.0  24 XIJANG
AUG 17
005208.5   4.522S  77.954W  51D 5.4     0.6  67 NORTHERN PERU
200405.3& 40.455N 124.397W   5                3 NEAR COAST OF NORTHERN CALIF.
        <BRK-P>. ML 3.1 (BRK). Felt at Eureka and Ferndale.
202436.5& 40.500N 124.270W   4                7 NEAR COAST OF NORTHERN CALIF.
        <BRK-P>. ML 3.3 (BRK). Felt at Eureka, Ferndale and Scotia.
204150.7  34.228N 116.904W   5G 4.6     0.6  27 SOUTHERN CALIFORNIA. ML 4.7
        (GS). Felt at Riverside, San Bernardino and in the Big Bear area. Also
        felt throughout much of the Los Angeles area and at San Diego.
        Rockslides reported in the Big Bear area.
210131.5  34.225N 116.828W   5G         0.5  13 SOUTHERN CALIFORNIA. MD 3.5
210925.0* 20.101S  68.558W 109D 5.3     0.6  46 CHILE-BOLIVIA BORDER REGION.
        Felt at Arica and Iquique, Chile.
AUG 18
050313.6* 20.562S  68.007W 113D 5.0     0.5  32 CHILE-BOLIVIA BORDER REGION
061557.8* 22.058S 174.564W  33N 5.0 5.2 0.6  24 TONGA ISLANDS REGION
094638.5  34.240N 116.853W   5G         0.7  16 SOUTHERN CALIFORNIA. MD 4.1
AUG 19
005745.1* 50.734N 174.658W  36? 6.1 5.7 1.0  73 ANDREANOF ISLANDS, ALEUTIAN IS.
        Mo=5.0*10**18 Nm (PPT). Felt at Adak and on Atka.
020438.1* 42.122N  73.583E  33N 6.6 7.5 1.0  62 KYRGYZSTAN. Mo=5.0*10**19 Nm
        (PPT). At least 42 people killed or missing, including 14 killed by
        landslides in Toluk. Several villages, including Toluk, were destroyed
        in the Susamyrtau Mountains and at least 7000 dwellings were destroyed.
        Felt (VII) at Andizhan and Namangan, Uzbekistan. Structural damage to
        buildings (VI) at Bishkek, Kyrgyzstan. Felt (VI) at Fergana and
        Tashkent, Uzbekistan and at Osh, Kyrgyzstan; (V) at Samarkand,
        Uzbekistan. Also felt at Alma-Ata, Kazakhstan.
031209.2? 42.56 N  73.08 E  33N 6.0     1.0  57 KYRGYZSTAN
032036.4? 43.30 N  72.89 E  33N 6.4     0.8  43 CENTRAL KAZAKHSTAN
021300  Q 42.5  N  74.2  E  33N 6.1     1.0  17 KYRGYZSTAN