From: greg@perry.berkeley.edu (Greg Anderson)
Newsgroups: sci.geo.geology,ca.earthquakes
Subject: N. CA, USA, and World Quake Report 9/3-9/92
Date: 11 Sep 1992 17:50:49 GMT
Organization: UC Berkeley
Distribution: world
NNTP-Posting-Host: perry.berkeley.edu
Originator: greg@perry.berkeley.edu

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
   September 3 - 9, 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, September 9,
1992 the U.S. Geological Survey office in Menlo Park recorded 21
earthquakes of magnitude one (M1) and greater within the San Francisco Bay
area shown in Figure 1.  Four were as large as M2.0.  The weekly total
compares with 24 earthquakes recorded during the previous 7-day period,
five of which were as large as M2.0. 
    The only noteworthy activity during the week was a small cluster of
earthquakes Saturday night 5 miles southeast of Mount Diablo (#3 in Fig.
1).  The cluster began with a M2.7 event about 8:30 that evening.  Six
hours later, four more small earthquakes occurred in the same location,
only one of which was as large as M2.0.  The earthquakes occurred near the
Mount Diablo fault that bounds Mount Diablo on the east.  A search of the
catalog shows only one M2 event had occurred in this location in the past
three years:  a M2.1 event in July, 1990.  
     The only other M2 events also occurred in the East Bay, both on the
central Calaveras fault.  Last Friday evening a M2.0 occurred about 11
miles north of Morgan Hill (#2/1).   Wednesday evening a M2.1 occurred 6
miles east-northeast of Milpitas, just southeast of the Calaveras
reservoir (#4/1).      

Northern California
    
     It was a relatively quiet week in northern and central California,
seismically speaking.  Aftershocks in the Cape Mendocino area declined to
their lowest number in weeks (#9/2) and the Geysers geothermal area
experienced only one earthquake as large as M2.  Farther north, near the
Oregon border, a M2.0 occurred Sunday morning about 7 miles northwest of
Crescent City (#5/2).  To the east a pair of M2 events occurred last
Thursday just east of Burney Falls, the largest a M2.8 event (#1/2).  In
the northern Sierra Nevada, a M2.7 occurred Friday evening 12 miles
southwest of Chester (#3/2) and a M2.0 occurred Wednesday morning 18 miles
north of Chico (#8/2). 
     The only area to show any elevated activity was the eastern Mono
Basin which has been active since the M7.5 Landers earthquake in late
June.  Three M2 events occurred here earlier in the week, the largest a
M2.8 events last Friday morning (#2/2). 
     On Saturday a M3.3 earthquake occurred in northern Chalfant Valley
about 15 miles north of Bishop (#4/2).  Eighty minutes later, a M3.6
occurred along the Round Valley fault about 12 miles southwest of the
Chalfant event (see #1 in Fig.3).  
    Activity in central California was limited to a M2.0 on the San
Andreas about 19 miles northeast of King City and a pair of M2.2 events
southeast and northwest of Avenal (#7/2). 

Long Valley Caldera
        
     Activity remained low both within the caldera and in the Sierra
Nevada terrane to the south.  Only six earthquakes larger than M1.5
occurred within the caldera, none as large as M2.0 (Fig. 3).  Three of
these occurred in the western end of the south moat; the remaining three
occurred along the south side of the resurgent dome.   The only notable
activity south of the caldera was a M3.6 that occurred Saturday afternoon
just east of the Round Valley fault (#1/3).  A M3.2 event occurred about
10 km northeast of this event in mid-June of this year.    
    
USA Seismicity
    
     According to data provided by the National Earthquake Information
Service, only one notable earthquake occurred in the lower 48 states
outside of California.  This M4.0 event occurred in the northern Wasatch
Range of southeastern Idaho and felt in the Soda Springs area (#1/4).  
     In California, notable events not mentioned above included a M3.8 in
the Coso volcanic center (#2/4), a M4.0 along the northern end of the
Landers aftershock zone, about 4 miles northeast of Barstow (#3/4), and a
M4.1 toward the southern end of the aftershock zone (#4/4).
        
The Planet Earth

     Aftershocks continued to be recorded from last week's deadly M7.0
earthquake off the coast of Nicaragua (#1/5).  However, none was larger
than M5.5 and no damaging tsunamis were generated.   The rest of the world
was rather quiet with no earthquakes recorded anywhere that were as large
as M6.  Even the western Pacific margin produced few earthquakes of any
size.  The largest were a M5.0 near the Santa Cruz Islands (#2/5) and a
M5.5 near the northern coast of New Guinea (#3/5).  The largest
earthquake of the week was a M5.7 on the oceanic spreading ridge southwest
of the Svalbard Islands (Spitsbergen)(#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 SEP  3 1612 56.98 41  2.59 121 38.93  6.65 23 2 .16  .5 3.3 SHA-  2.4
92 SEP  3 2100 27.19 41  2.81 121 38.40 10.55 28 3 .19  .5 1.9 SHA   2.9
92 SEP  4  345 57.09 38  1.71 118 43.52  9.01 29   .11 1.0 3.1 MOL-  2.2
92 SEP  4  421 40.98 38 16.23 118 17.03  8.24  8   .1612.014.3 NEV - 2.2
92 SEP  4  851  3.72 36 28.30 121  2.69  5.48 30   .06  .2  .8 BIT   2.0

92 SEP  4 1500 55.06 38  2.70 118 43.05  4.28 28   .10  .8 4.2 MOL   2.8
92 SEP  4 1630  7.53 38  1.19 118 43.62  7.60 15   .14 1.1 6.1 MOL   2.1
92 SEP  5  123  6.48 40  8.98 121 19.17 11.52 36 2 .19  .5 1.1 ALM   2.9
92 SEP  5  133 34.55 37 16.68 121 39.15  7.35 35 2 .05  .2  .5 SFL   2.0
92 SEP  5 2011  5.37 37 34.50 118 26.85  8.77 33   .07  .3  .6 CHV   3.3

92 SEP  5 2228  8.50 37 27.30 118 35.92  9.17 35 1 .13  .3  .7 RVL   3.5
92 SEP  6  334  5.76 37 52.50 121 50.03 15.46 92 4 .20  .3  .3 GRN   2.7
92 SEP  6  833 15.09 39 27.05 119 55.53  0.16 13 1 .24 2.3 2.6 WAK * 2.6
92 SEP  6  924 43.32 37 52.43 121 49.77 15.45 45 3 .17  .4  .7 GRN   2.1
92 SEP  6  935 52.68 39 17.35 118  8.92 22.08 33 1 .50 9.618.4 NEV   3.2

92 SEP  6 1753  0.32 41 51.18 124 17.16 27.92  7 1 .08 1.3 2.1 PON   2.0
92 SEP  6 2015 56.94 40 30.44 124 52.93 20.59 14   .10 3.2 2.1 MEN   2.0
92 SEP  7   27 51.29 40 19.24 125  8.57  5.24 12   .09 6.7 6.4 MEN - 1.9
92 SEP  7  649  6.37 38  0.23 118 20.20  5.00 22   .13 2.211.1 MOL - 2.1
92 SEP  7 1418 13.79 37 58.71 118 21.30  1.18 11 1 .13 3.9 3.8 MOL   2.2

92 SEP  7 1522 23.29 40 21.18 124 22.69 16.20 18 1 .14  .7  .3 MEN   2.1
92 SEP  8  931  0.69 38 47.50 122 46.01  0.61 13   .05  .2  .7 GEY   2.2
92 SEP  9  506 49.60 40 18.17 124 24.18  7.78 20 1 .15  .8  .4 MEN   2.0
92 SEP  9  643 46.11 40 18.11 124 24.63  8.19 19 1 .14  .9  .5 MEN   2.1
92 SEP  9 1150  0.65 35 49.96 119 58.11  6.22 29 2 .31  .8  .8 COA   2.4

92 SEP  9 1342 28.25 40  1.43 121 47.53 23.80 24 1 .13  .5  .9 ALM   2.3
92 SEP  9 2137 15.22 40 22.18 124 21.28  9.65 20   .15  .7  .4 MEN   2.8
92 SEP  9 2344  3.32 36  3.59 120 12.93 15.05 19   .27  .7 1.9 COA   2.2
92 SEP 10   45 17.82 37 27.41 121 48.55  6.53 46   .14  .3  .7 ALU   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
-----------------------------------------------------------------------------
SEP 03
075125.6* 11.543N  87.093W  33N 4.8     1.2  51 NEAR COAST OF NICARAGUA
080630.3* 11.027N  86.797W  33N 4.4     1.2  21 NEAR COAST OF NICARAGUA
112417.1? 11.35 N  87.11 W  33N 4.4     1.1  32 NEAR COAST OF NICARAGUA
133308.6? 12.14 N  88.18 W  33N 4.6     1.2  20 OFF COAST OF CENTRAL AMERICA
134211.4  50.703N 129.821W  10G 4.2     1.2  33 VANCOUVER ISLAND REGION

SEP 04
002124.6* 11.523N  87.836W  33N 5.2 4.7 1.0  64 NEAR COAST OF NICARAGUA
012548.5? 11.82 N  87.87 W  33N 4.5     1.1  18 NEAR COAST OF NICARAGUA
045414.8  42.680N 111.411W   5G 3.9     0.6  32 EASTERN IDAHO. ML 4.0 (GS). Felt
                                                in the Soda Springs area.
092350.1? 11.14 N  87.09 W  33N 4.4     1.1  15 NEAR COAST OF NICARAGUA
135729.2* 12.792S 166.614E 149D 5.0     0.9  29 SANTA CRUZ ISLANDS
150257.7  36.081N 117.796W   5G         0.8  17 CALIFORNIA-NEVADA BORDER REGION.
                                                ML 3.8 (GS). MD 3.6 (PAS).
161607.3? 11.09 N  87.75 W  33N 4.7     1.2  15 NEAR COAST OF NICARAGUA
165156.6? 11.92 N  88.21 W  33N 5.1     1.1  28 OFF COAST OF CENTRAL AMERICA
232135.6? 52.42 N 179.64 E 189* 4.5     0.9  22 RAT ISLANDS, ALEUTIAN ISLANDS

SEP 05
032925.3  34.097N 116.384W   5G         0.6  16 SOUTHERN CALIFORNIA. MD 3.8
                                                (PAS). ML 3.7 (GS).
091440.1  41.569N 142.540E  33N 4.8     1.3  30 HOKKAIDO, JAPAN  REGION
103327.7? 11.69 N  87.63 W  33N 4.6     0.8  27 NEAR COAST OF NICARAGUA
200641.7?  3.77 S 142.44 E  44D 5.5     1.0  17 NEAR N COAST OF NEW GUINEA, PNG.
214812.7* 11.617N  87.318W  33N 5.3 5.8 1.1  74 NEAR COAST OF NICARAGUA.
222808.0  37.500N 118.649W   5G         0.7  14 CALIFORNIA-NEVADA BORDER REGION.
                                                ML 3.1 (GS).
234313.3  34.232N 116.395W   5G         0.7  12 SOUTHERN CALIFORNIA. MD 3.2

SEP 06
013016.6? 11.71 N  87.44 W  33N 4.5     0.9  15 NEAR COAST OF NICARAGUA
131239.4* 11.563N  87.378W  33N 5.5 5.2 1.0  64 NEAR COAST OF NICARAGUA
141336.0? 11.44 N  87.32 W  33N 4.8     1.1  41 NEAR COAST OF NICARAGUA
152352.4  34.955N 116.911W   5G         0.6  11 SOUTHERN CALIFORNIA. MD 3.1
175105.7  34.003N 117.195W  10G         0.5  13 SOUTHERN CALIFORNIA. MD 3.4
        (PAS). ML 3.4 (GS). Felt at Riverside.
221651.8  34.082N 117.081W   5G         0.9  11 SOUTHERN CALIFORNIA. MD 3.0
224728.4  34.985N 116.967W   5G         0.7  14 SOUTHERN CALIFORNIA. MD 3.4

SEP 07
115325.5* 16.984N  99.182W  33N 4.6     0.9  36 NEAR COAST OF GUERRERO, MEXICO
153738.4  60.877N 147.048W  33N         0.9  11 SOUTHERN ALASKA
190210.7? 11.62 N  87.01 W  33N 4.6     1.2  37 NEAR COAST OF NICARAGUA
225715.7  59.746N 152.223W  87*         0.5  12 SOUTHERN ALASKA

SEP 09
114454  Q 35.0  N 117.0  W   5G         0.9  24 CENTRAL CALIFORNIA. ML 4.0 (GS).
125043  Q 33.9  N 116.3  W   5G         1.0  24 SOUTHERN CALIFORNIA. ML 4.1
130855  Q 76.2  N   6.7  E  20      5.7 0.8  71 SVALBARD REGION

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