From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Newsgroups: sci.geo.geology,ca.earthquakes
Subject: N. CA, USA, and World Quake Report 11/12-18/92
Date: 20 Nov 1992 09:45:51 GMT
Organization: Stanford Univ. Earth Sciences
Distribution: world
NNTP-Posting-Host: pangea.stanford.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
November 12 - 18, 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     
    
    During the 7-day period ending at midnight on Wednesday, November 18,
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 including a M3.4
event along the central Calaveras fault.  This week's total compares to 24
earthquakes that were recorded during the previous 7-day period, five of
which were as large as M2. 
    The M3.4 Calaveras earthquake occurred early Saturday morning about 9
miles east of San Jose (#4 in Fig. 1).  It was felt by many in the San
Jose and Alum Rock areas.  It was followed 15 minutes later by the a M1.1
aftershock, the lone aftershock recorded.  A M2.8 occurred about 8 km to
the southeast late Sunday night, also along the Calaveras. 
    Two earthquakes also occurred along the Hayward fault during the week,
the largest a M2.5 Saturday evening that was located about 3 miles north
of Fremont (#3/1).  A M2.2 occurred in the same area in early February of
this year.  On Sunday morning a M1.2 occurred on the northern Hayward
segment about 3 miles east of Berkeley.  
    The San Andreas was also active during the week.  The creeping segment
around San Juan Bautista produced several small earthquakes during the
week, the largest a M2.1 last Thursday afternoon (#1/1).  A small cluster
of five earthquakes occurred last Friday morning along the southern end of
the Black Mountain thrust fault, 11 miles west of San Jose (#2/1).   The
largest of these was only M1.8, typical of the small earthquakes that
frequently occur along this small fault.  Finally, a small earthquake
occurred Saturday afternoon on or near the San Andreas about 4 miles north
of Pacifica (#5/1).  
    
Northern California

   Seismicity was again rather low throughout much of northern and central
California during the past week.  With the exception of the creeping
segment, the San Andreas was entirely quiet at the M2 level.  The creeping
segment, active at the north end near San Juan Bautista (see above), was
also active throughout it's length.  The largest of the creeping segment
earthquakes was a M2.8 in the Slack Canyon area, the southern end of the
creeping zone that bounds the Parkfield segment to the south (#7/2).  A
pair of M2 events occurred off the San Andreas about 17 miles east of
Coalinga (#3/2).
   In the Cape Mendocino area there was only one earthquake as large as
M2, a M2.7 event that occurred about 25 miles offshore near the base of
the continental slope (#4/2).  Onshore, the only notable event was a M2.4
31 miles east-northeast of Eureka (#8/2).  With a focal depth of about 26
km, it is likely that this earthquake occurred within the subducted Gorda
Plate that underlies much of northern California north of about 40 degrees
latitude. 
     In eastern California activity was seen both within the Long Valley
caldera (discussed below) and along it's margins.  The peripheral
seismicity included a pair of M2 events east of Mono Lake (#1/2), a M2.8
in the northern Chalfant Valley (#6/2), and a M2.5 in the eastern Sierra
Nevada terrane south of the caldera (#2/2).  The only other activity of
note was a M3.3 along the Sierran frontal fault about 6 miles east of
Markleeville (#5/2).  This is the same location as a small swarm that
occurred in early May of this year and included seven M3 events.
        
Long Valley Caldera
    
       The only M2 earthquake within the caldera was a M2.6 event that
occurred just after midnight last Friday.  It was located about 1 mile
southeast of Mammoth Lakes (#1/3).  A small cluster of earthquakes
occurred later in the week along the southwestern boundary of the caldera
about 3 miles south-southwest of Mammoth Lakes (#2/3).  Two of these were
as large as M2.   A similar episode occurred in almost the same location
in early July, 1991.  Like the recent activity, it was capped by a pair of
M2's.   Activity remained low in the area south of the caldera.  Three
earthquakes larger than M1.5 were located in this area, only one of which
was as large as M2 (#3/3).

USA Seismicity

    According to data provided by the National Earthquake Information
Service, the only notable earthquakes in the lower 48 states to occur
outside of the California area were a pair of M3 events in eastern Idaho
(#1/4).   Both occurred last Thursday about 40 miles east of Blackfoot. 
Notable activity in southern California consisted of a pair of M3's just
each of Barstow (#2/4) and a M3.6 in approximately 10 miles southeast of
Redlands (#3/4). 
            
The Planet Earth

   Seismicity declined worldwide during the past week, both in terms of
the number of earthquakes and in the number of large earthquakes.  The
largest earthquake during the past week was a M6.1 in central Greece on
Wednesday (#5/5).   A M4.3 occurred in the eastern Aegean Sea earlier in
the week that was felt on the Greek Islands of Lesvos and Khios (#1/5).  A
M5.6 occurred in the Hindu Kush region of northeastern Afghanistan (#2/5). 
The western Pacific was largely quiet except for a several moderate
earthquakes in the Fiji Islands, the largest a M5.8 (#3/5).  In the
western hemisphere, notable activity was limited to a M5.5 in the Chile-
Argentina Border region (#4/5) and couple of M4.5 events off the coasts of
El Salvador and Nicaragua.  
     
 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 NOV 12 2131  1.45 36 32.06 121  6.67  2.28 30   .06  .2  .9 PIN   2.4
92 NOV 12 2206  4.15 36 53.80 121 37.01  2.90 24   .10  .3  .6 SJB   2.1
92 NOV 13  652  5.25 37 59.49 118 43.42  4.46  9   .11 1.8 3.7 MOL   2.0
92 NOV 13 1221 55.22 37 15.23 118 39.02  7.49 31   .08  .4 1.3 KAI   2.5
92 NOV 13 1916 55.58 36  7.76 120  2.32  8.50 10   .22 1.8 1.1 COA   2.3

92 NOV 14  435 46.56 38 47.76 122 44.73  2.56 37   .14  .3  .7 GEY   2.5
92 NOV 14  651 36.80 37 34.85 121 57.60 10.83 88   .16  .2  .4 HAY   2.5
92 NOV 14  841 48.52 37 38.07 118 57.35  7.11 32   .13  .3  .5 SMO   2.6
92 NOV 14  957 46.20 37 21.84 121 43.76  6.39108   .16  .2  .4 ALU   3.4
92 NOV 14 1818 20.09 40 30.93 124 46.36 21.16  8   .12 4.1 1.5 EUR * 2.7

92 NOV 15   36 26.30 38 40.49 119 40.15  0.31 29   .17  .8 2.1 WAK * 3.3
92 NOV 15 1032 45.35 36 10.20 120  4.88  8.47 31   .19  .8  .8 COA   2.1
92 NOV 15 2042 49.65 38  1.03 118 36.14  3.48 10   .08 1.1 3.7 MOL   2.2
92 NOV 16   23 43.94 37 31.08 118 24.57  7.34 25   .08  .3  .7 CHV   2.8
92 NOV 16  331 38.99 36  1.57 120 35.02  5.34 60   .16  .2  .4 SLA   2.8

92 NOV 16  747 40.09 37 18.95 121 41.09  7.25107   .14  .2  .4 SFL   2.8
92 NOV 16 1222 19.70 37 36.60 118 59.12  7.10 23   .10  .3  .5 MAM   2.2
92 NOV 16 1911 58.85 36 24.71 120 59.37  5.57 26   .08  .3  .7 BIT   2.0
92 NOV 17  534 28.58 36 15.03 120 48.87  7.35 31   .19  .4  .9 BIT   2.0
92 NOV 17 1020 34.30 37 33.46 118 51.09 10.19 29   .09  .3  .6 MOR   2.1

92 NOV 17 1048 20.83 41  0.95 123 40.41 26.26  7   .10  .7 2.0 EUR   2.4
92 NOV 18 1408 29.44 37 36.79 118 59.10  7.26 19   .11  .4  .6 MAM   2.0

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
------------------------------------------------------------------------------
NOV 12
124519.6* 17.176S 179.091W 500G 4.6     0.6  40 FIJI ISLANDS REGION
134442.2  52.993N 176.165W 225  5.0     1.1  79 ANDREANOF ISLANDS, ALEUTIAN IS.
151108.8  38.650N  26.535E  10G 4.3     0.5  16 AEGEAN SEA. ML 4.6 (THE). Felt
                                                on Lesvos and Khios, Greece.
151910.1% 38.682N  26.561E  10G         0.6  12 AEGEAN SEA. ML 4.3 (THE). Felt
                                                on Lesvos and Khios, Greece.
165032.6? 11.87 N  87.31 W  33N 4.5     1.2  19 NEAR COAST OF NICARAGUA
165310.3*  5.010S 152.473E  33N 5.1 4.9 1.3  15 NEW BRITAIN REGION, P.N.G.
185356.3  43.001N 111.601W   5G         1.2  11 EASTERN IDAHO. ML 3.2 (GS).
204104.7  36.408N  70.806E 200D 5.6     0.8  59 HINDU KUSH REGION, AFGHANISTAN
213103.3  43.117N 111.445W   5G         0.8   9 EASTERN IDAHO. ML 3.1 (GS).
222900.3* 21.856S 178.377W 370D 5.8     0.8  26 FIJI ISLANDS REGION

NOV 13
020148.9  43.046N 111.534W   5G         0.6  11 EASTERN IDAHO. ML 3.3 (GS).
062542.9? 13.28 N  88.46 W  33N 4.5     1.1  22 EL SALVADOR

NOV 14
070102.5  34.938N 116.977W   5G         1.0  22 SOUTHERN CALIFORNIA. MD 3.4
071715.3  34.923N 116.943W   5G         0.9  23 SOUTHERN CALIFORNIA. MD 3.3
081925.1* 25.915S 179.230E 500G 4.5     0.6  28 SOUTH OF FIJI ISLANDS
120302.0* 51.524N 176.213W  48D 4.8     1.3  42 ANDREANOF ISLANDS, ALEUTIAN IS.
154414.0? 22.42 S 177.03 W  33D 4.5     1.3  28 SOUTH OF FIJI ISLANDS

NOV 17
042416  Q 30.4  S  70.8  W  50  5.5     0.6  67 CHILE-ARGENTINA BORDER REGION

NOV 18
141009  Q 34.0  N 117.0  W  10G         0.9  17 SOUTHERN CALIFORNIA. ML 3.6
211042  Q 38.4  N  22.3  E  10G 6.1     0.9  42 GREECE
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