From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Newsgroups: sci.geo.geology,ca.earthquakes
Subject: N. CA, USA, and World Quake Report 10/8-14/92
Date: 16 Oct 92 21:06:34 GMT
Organization: Stanford Univ. Earth Sciences

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
   October 8 - 14, 1992

Data and text prepared by
  Steve Walter, Barry Hirshorn, 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, October 14, 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.  Two of these were as large as M2.0 including a M3.3 event on
the San Andreas near Watsonville.  This week's total compares to the 28
earthquakes recorded during the previous 7-day period, three of which were
as large as M2. 
    The week's largest earthquake occurred last Thursday evening on the
Loma Prieta segment of the San Andreas, about 4 miles northeast of
Watsonville (#1 in Fig. 1).   The earthquake, felt by residents of the
Watsonville area, was an aftershock to the M7.1 Loma Prieta earthquake
that occurred almost three years ago.  Another aftershock of similar
magnitude occurred several miles to the southeast of this recent event on
September 15.  
    In the East Bay seismicity was primarily along the central Calaveras
fault although no earthquakes here were as large as M2.  The only M2 in
the East Bay occurred Saturday morning, a M2.0 event almost directly below
Walnut Creek (#2/1).  It was preceded 15 minutes earlier by a M1.4 in the
hills north of Livermore.
          
Northern California
  
   Several felt earthquakes occurred in northern California during the
past week.  The first was a M3.7 event last Thursday evening in the
Petrolia area, an aftershock to the M7.1 Cape Mendocino earthquake that
caused extensive damage in the area in late June (#1/2).  A second
aftershock was felt Sunday evening; the epicenter of this M3.2 event was
about seven miles west of Petrolia.  The largest earthquake of the week
occurred Saturday morning in the Adobe Valley area east of Mono Lake
(#5/2).  Because of the remoteness of this area, the quake was not widely
reported.   The most widely felt earthquake occurred Wednesday afternoon: 
a M3.6 temblor beneath the northern Sacramento Valley, about 15 miles
west-southwest of Chico (#9/2).  This is the largest earthquake to occur
here in at least the past two years although occasional M2 earthquakes
have been observed in the area during this period.
   For the second consecutive week several exceptionally deep events
occurred beneath the western Klamath Mountains and beneath the central
Sierra Nevada southwest of Yosemite.  The first of the Klamath events was
a M2.5 that occurred last Friday afternoon about 32 miles southeast of
Crescent City at a depth of 34 km (#2/2).  Two more deep earthquakes
occurred east of Eureka, the first Sunday afternoon, the second early
Wednesday morning (#6/2).  Both had similar focal depths of approximately
28 km.  All three deep earthquakes are believed related to subduction of
the Gorda Plate beneath northern California.  
    The deep earthquakes beneath the central Sierra Nevada are less well
understood.  The first to occur this week was a M2.0 event that occurred
last Friday evening at a depth of 31 km about 27 miles north-northeast of
Madera (#4/2).  This is just 2 km shallower and several miles southwest of
a 33-km deep earthquake reported in last week's summary.  Interestingly,
the M2 event was followed on Monday afternoon by an even shallower
earthquake, a M2.4 that occurred at a depth of 28 km about 13 miles south-
southeast of Merced (#7/2).   
        
Long Valley Caldera
     There was a slight increase in seismicity within the caldera as a
result of a small cluster of events last Thursday.  The activity occurred 
in the south moat area about 1 mile southwest of the Fish Hatchery and was
capped by a M2.0 event (#1/3).  The same day a M2.3 occurred beneath the
west side of the resurgent dome about 2 miles northeast of Mammoth Lakes
(#2/3). 
      Activity declined in the Sierra Nevada terrane south of the caldera. 
The only notable activity here was a M2.7 that occurred Wednesday evening
about 1 mile southeast of Convict Lake (#4/3). 
     Finally, to the east of the Sierra Nevada range, a M3.1 earthquake
occurred Tuesday morning in the Round Valley area (#3/3; also #8/2). 
Although it occurred only 10 miles west-northwest of Bishop no reports
were received that this earthquake was felt locally.
     
 USA Seismicity

    According to the National Earthquake Information Service, the only
notable earthquake in the lower 48 states, outside of California, was a   
M4.0 in central Wyoming (#1/4).   This event occurred east of the Wind
River Range and was felt in the Lander area.  The only notable California
earthquakes, aside from those discussed above, occurred in the area east
of Barstow (#3/4).  This area ruptured during the Landers sequence in late
June and has been active since.  The largest aftershock during the past
week was a M4.4 event early Sunday morning that was felt at Barstow.  
            
The Planet Earth

    The most noteworthy earthquake during the past week was by no means
the largest.  Monday a Mb5.9 earthquake struck beneath the western
environs of Cairo, Egypt (#6/5).  This is the largest earthquake to strike
the Cairo area in many years and it caused serious injury and damage.  At
least 390 people have been reported killed, over 3,000 injured, and at
least 84 buildings have been destroyed in the Cairo area.   The
earthquake was felt throughout much of Egypt as far south as Aswan, and
in Israel at Jerusalem and Tel Aviv.  
    The largest earthquake of the week was a Ms6.9 event in the Vanuatu
Islands, southeast of the island capitol of Port Vila (#5/5).  The Vanuatu
Islands experience regular, large earthquakes; the most recent large
earthquake was a M7.0 in February of this year.  Other notable earthquakes
in the southwest Pacific include a M5.1 in the Tonga Islands (#4/5) and a
M5.0 in the Solomon Islands.  In the northern Pacific, the Andreanof
Islands have continued to be active for the third straight week, following
a Ms6.5 in late September.  The largest earthquakes during the past week
were a pair of M5 aftershocks that were felt on Adak island (#1/5).  
    In the western hemisphere only three earthquakes occurred that were as
large as M5; two of these were Mb5.1 events that occurred in the same
location near the coast of northern Chile (#3/5).  The third, also Mb5.1
occurred beneath the equatorial Atlantic, along the mid-Atlantic ridge
(#2/5).   A pair of M4 earthquakes occurred Sunday beneath the central
Gulf of California, aftershocks to a Ms5.3 earthquake that occurred a week
earlier (#2 in Fig. 4).
      

 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 OCT  8  751 45.01 38 13.66 119 15.04  7.01  8 2 .21 2.116.9 WAK - 2.7
92 OCT  8 2032 21.31 37 37.72 118 52.81  8.47 30 1 .11  .3  .5 SMO   2.3
92 OCT  8 2344 38.79 37 40.38 118 56.56  3.07 36 1 .14  .3  .5 SMO   2.6
92 OCT  9   20 30.93 36 56.16 121 41.36 13.42121 8 .16  .2  .3 SJB   3.3
92 OCT  9  223 48.66 40 27.44 124 16.82 19.31 26 2 .12  .4  .2 MEN   3.7

92 OCT  9  443  2.23 38 48.69 122 49.22  2.70 31   .14  .2  .6 GEY   3.0
92 OCT  9  845 33.71 37 55.70 118 37.98  3.41 28   .11 1.3 2.0 MOL-  2.2
92 OCT  9  919 36.01 38 27.67 119 30.57  8.53 14 1 .18 1.310.3 WAK   2.4
92 OCT  9  932 55.58 38 48.61 122 46.15  2.83 26   .11  .2  .6 GEY   2.4
92 OCT  9 1106 12.00 40 24.48 124 34.46 13.88 15 1 .15 1.4  .4 MEN   2.3

92 OCT  9 2214 27.91 41 25.86 123 47.05 34.21 13   .14  .6 1.4 KLA   2.5
92 OCT 10  144  5.56 39 55.69 122 51.50  1.83 36   .53  .7 2.9 SAC   2.5
92 OCT 10  349 17.39 37 20.59 119 56.49 30.84  9 1 .18 1.6 4.0 KAI   2.4
92 OCT 10 1536 59.42 37 54.98 122  2.74 10.50 46 3 .21  .3  .5 CON   2.1
92 OCT 10 1754 51.18 38  0.21 118 34.43  1.57 26   .09 1.6 7.9 MOL - 3.9

92 OCT 11 1116 19.02 40 24.64 124 24.55 21.02 21 1 .14  .9  .2 MEN   2.2
92 OCT 11 1830 11.75 40 24.92 124 25.16 10.30 12   .11 1.0  .4 MEN   2.4
92 OCT 11 2324 35.31 40 46.23 123 39.29 27.97 22 2 .12  .4  .8 EUR   2.0
92 OCT 12  234 25.16 40 17.04 124 24.89 21.85 24 1 .16 1.3  .4 MEN   3.2
92 OCT 12  812 24.93 38 47.38 122 46.75  0.04  7   .10  .4 1.7 GEY * 2.4

92 OCT 12  834 12.02 38 48.19 119 45.81  0.31 20 1 .13  .9 2.1 WAK * 2.4
92 OCT 12 1453 58.77 38 47.68 122 46.47  0.74 20   .09  .2  .6 GEY   2.2
92 OCT 12 1528  1.52 40 20.30 125  5.21  7.74 15   .2010.9 8.9 MEN-- 2.0
92 OCT 12 1855 43.65 36 32.69 121  7.87  5.24 28   .04  .2  .7 PIN   2.1
92 OCT 12 2206 36.63 37  8.59 120 21.73 28.48 23 4 .24  .6 2.0 JQN   2.6

92 OCT 12 2232 22.28 40 25.79 124 35.48 14.43 13 1 .15 1.9  .5 MEN   2.0
92 OCT 13   16 40.45 40 17.69 124 32.83 21.31  8   .08 2.8  .6 MEN   2.6
92 OCT 13 1143 50.33 37  6.12 121  5.37  2.39 31 1 .17  .6 4.4 ORT   2.3
92 OCT 13 1558 39.49 37 26.28 118 33.38 11.19 37 4 .09  .3  .6 RVL   3.1
92 OCT 14  759 49.51 38  2.06 118 45.83  7.47 16 8 .19  .712.9 MOL - 3.7

92 OCT 14  935 11.32 38 48.32 122 47.76  4.24 29   .15  .3  .6 GEY   2.3
92 OCT 14 1155 27.88 40 38.58 123 52.89 27.11 27 2 .11  .3  .7 EUR   2.9
92 OCT 14 2208 47.41 39 43.67 122  5.77 17.44 51   .31  .4  .9 SAC   3.6
92 OCT 15  149 36.77 38 41.33 118 47.13  1.97 23   .14 2.511.1 WAK - 3.4
92 OCT 15  208 16.11 37 34.46 118 50.01 13.08 22   .11  .5 1.0 MOR   2.7

92 OCT 15  235 17.43 38 42.05 118 47.53  1.63 19   .14 1.711.8 WAK - 2.9
92 OCT 15  308 15.08 38 44.28 118 45.26  0.63 24   .21 2.0 7.7 WAK   2.7

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
------------------------------------------------------------------------------
OCT 08
094952.1? 46.34 N 143.38 E 328D 4.8     0.6  54 SAKHALIN ISLAND
163456.2  51.186N 177.807W  44D 5.4 5.7 1.0  97 ANDREANOF ISLANDS, ALEUTIAN IS.
                                                Felt on Adak.
174458.8  36.020N 117.595W   5G         0.9  19 CALIFORNIA-NEVADA BORDER REGION.
                                                MD 3.6 (PAS). ML 3.5 (GS).
194238.3? 51.09 N 178.09 W  33N 4.5     1.0  20 ANDREANOF ISLANDS, ALEUTIAN IS.

OCT 09
002031.2& 36.885N 121.735W  10               12 CENTRAL CALIFORNIA. <BRK-P>. 
004200.7* 51.153N 178.071W  33N 4.6     1.0  44 ANDREANOF ISLANDS, ALEUTIAN IS.
011058.6* 51.217N 177.960W  46D 4.7     0.9  36 ANDREANOF ISLANDS, ALEUTIAN IS.
022347.3* 40.434N 124.316W  20G         0.8  15 NEAR COAST OF NORTHERN CALIF. ML
        3.5  Felt at Arcata, Eureka, Ferndale, Fortuna, Honeydew, & Petrolia

044302.9  38.803N 122.687W   5G         1.0  10 NORTHERN CALIFORNIA. ML 3.1
093450.4?  0.96 S  15.99 W  10G 5.1 5.1 0.9  21 NORTH OF ASCENSION ISLAND
121654.8  51.498N 176.799W  34D 5.3 4.8 1.2  79 ANDREANOF ISLANDS, ALEUTIAN IS.
                                                ML 5.2 (PMR). Felt (IV) on Adak.
144219.9* 51.159N 178.159W  33N 4.5     1.0  35 ANDREANOF ISLANDS, ALEUTIAN IS.
162516.5  60.023N 149.191W  10G 4.1     0.8 101 KENAI PENINSULA, ALASKA. ML 4.2
        (PMR), 3.9 (AEIC). Felt (IV) at Seward; (III) at Anchorage & Eagle River

OCT 10
010020.8* 25.504S  70.042W  34D 5.1 4.3 0.6  48 NEAR COAST OF NORTHERN CHILE
040058.9* 54.692N 162.467E  33N 4.8 4.4 0.7  35 NEAR EAST COAST OF KAMCHATKA
055227.4* 25.537S  70.154W  31D 5.1 4.3 0.7  47 NEAR COAST OF NORTHERN CHILE
095011.9  20.355S 173.206W  33N 5.1 4.6 0.7  50 TONGA ISLANDS
151048.4* 10.143S 161.048E  98D 5.0     0.8  39 SOLOMON ISLANDS
154056.1  42.875N 108.296W   5G         0.8  17 WYOMING. ML 4.0. Felt at Lander.
175451.1  38.029N 118.562W   5G         0.6  20 CALIFORNIA-NEVADA BORDER REGION.
                                                ML 4.1 (GS), 4.0 (BRK).
234513.8? 22.49 S 178.87 E 561D 4.4     1.0  17 SOUTH OF FIJI ISLANDS

OCT 11
005541.9* 27.193N 111.780W  10G 4.2     1.1  20 GULF OF CALIFORNIA
072752.4* 51.620N 178.081E  75D 4.1     1.0  20 RAT ISLANDS, ALEUTIAN ISLANDS
123811.2  34.904N 116.816W   5G 4.0     0.9  28 SOUTHERN CALIFORNIA. MD 4.4
        (PAS). ML 4.2 (GS). Felt at Barstow.
145006.3  27.523N 111.508W  10G 4.8 4.8 1.0  51 GULF OF CALIFORNIA
192415.7  18.918S 168.798E  33N 6.7 6.9 0.8  70 VANUATU ISLANDS.
223453.8  34.917N 116.775W   5G         0.7  21 SOUTHERN CALIFORNIA. MD 3.5
232034.6  50.436N 153.257E 283D 5.5     0.7 122 KURIL ISLANDS

OCT 12
130957.7  30.050N  31.184E  25D     5.4 0.8  79 EGYPT. mb 5.9 (GS). At least 390
        people killed, 3,000 injured and 84 buildings destroyed in the Cairo
        area. Felt throughout much of Egypt as far south as Aswan. Also felt at
        Jerusalem and Tel Aviv, Israel.
OCT 14
220847  Q 39.7  N 122.1  W  10G              11 NORTHERN CALIFORNIA. ML 3.2