From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Newsgroups: sci.geo.geology,ca.earthquakes
Subject: N. CA, USA, and World Quake Report 12/17-23/92
Date: 24 Dec 1992 23:10:38 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
 December 17 - 23, 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, December 23,
1992 the U.S. Geological Survey office in Menlo Park recorded 19
earthquakes of magnitude one (M1) and greater within the San Francisco Bay
area shown in Figure 1.  Three were as large as M2.0 including a M3.6
earthquakes on the Hayward fault.  This total compares to 35 earthquakes
that were recorded during the previous 7-day period, eight of which were
as large as M2. 
    The M3.6 Hayward earthquake occurred early Sunday afternoon about 3 km
north of Lake Chabot near the border of San Leandro and south Oakland (#2
in Fig.1). The earthquake was preceded two days earlier by a M1.5 shock
and was followed in the next day or so by two M1 aftershocks. The
mainshock was large enough to be felt in much of the central Bay Area and
to produce minor damage in the immediate area of the epicenter.  According
to press reports the damage was mostly limited to cracked chimneys, about
a dozen of which will have to be torn down and replaced.  The USGS
earthquake catalog shows this area has produced numerous small quakes in
the past 25 years, the largest a M4 event.  The most recent M3 earthquake
to occur here was in late 1989, several weeks after the Loma Prieta quake.
More recently, there was a M2.6 event in the same location in January,
1991.  
    The only other earthquakes worth noting were a pair of M2.0 events on
the creeping segment of the San Andreas near San Juan Bautista (#1/1). 
They occurred in the same area that has been active in recent weeks and
that produced five M3 earthquakes on December 10-12.    
        
Northern California

    The past week was fairly quiet throughout much of northern and central
California.  Except for the Hayward earthquake mentioned above, there were
no earthquakes as large as M3 in the area of California shown in figure 2.
    Northern California was exceptionally quiet with only a couple of M2
events along the Mendocino fracture zone (#2/2) and one M2.2 event beneath
the Klamath Mountains (#5/2).  The latter event occurred at a depth of
about 33 km, indicating it was related to the subduction of the Gorda
Plate beneath this part of northern California.  To the east, a M2.7
earthquake occurred last Thursday on the California-Nevada border (#1/2)
and a M2.5 occurred Tuesday west of Truckee (#6/2).  
    Central California was equally quiet with a trio of M2 events near
Coalinga (#3/2) and a M2.8 on the creeping segment of the San Andreas
about 17 miles northeast of King City (#4/2).
      
Long Valley Caldera
    
    Activity continued at a low level both within the caldera and in the
mountainous terrane south to the south.  During the past week there were
two M2 earthquakes in the south moat area of the caldera, each accompanied
by several smaller events.  The first of these was a M2.2 event last
Thursday morning that occurred about 4 miles east of Mammoth Lakes (#1/3).
The second M2 earthquake, a M2.6 event, occurred Saturday afternoon near
the airport (2/3).  
    South of the caldera there was a M2.9 Saturday night just west of
Convict Lake (#3/3).  On Wednesday three M2 earthquakes occurred southeast
of Mt. Morrison, the largest a M2.9 (#4/3).
 
USA Seismicity

   According to information supplied by the National Earthquake
Information Service (NEIS) there were no notable earthquakes in the lower
48 states, outside of California, during the past week.  In California,
M3 earthquakes were recorded on the Hayward fault in the Bay Area (see
above) and on the Landers aftershock zone east of Los Angeles.  The
largest of the Landers aftershocks was a M3.7 event that occurred early
Monday morning (#1/4).
            
The Planet Earth

  After last week's devastating earthquake and subsequent tsunami in the
central Indonesian archipelago, much of the northern edge of the Indo-
Australian plate appears to have become active.  Along with at least two
M5 aftershocks in the Flores region there was a Ms7.0 earthquake beneath
the Banda Sea that was felt as distant as northern Australia but that
apparently produced little damage (#5/5).  In addition a Ms6.1 occurred
beneath eastern Papua New Guinea (#2/5), a Ms5.9 occurred in the Santa
Cruz Islands, and a Ms6.4 occurred in the Samoan Islands region. 
    In the northern Pacific, a Mb6.1 earthquake occurred near the east
coast of Kamchatka (#4/5) and a Mb5.7 occurred in the Rat Islands of the
central Aleutians.  Central and western Asia also saw some seismicity with
a Mb5.8 in southern Iran (#1/5), a Mb5.2 near the Afghanistan-Tajikistan
border, and a Mb4.3 on the Romania-Yugoslavia border.   
    The largest earthquakes in the western hemisphere were a Mb5.1 off the
coast of Jalisco, Mexico and a Mb5.2 in the Chile-Bolivia border region
that was widely felt in both countries and produced landslides in El
Morro, Chile (#6/5). 

   
 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 DEC 17 1615 53.00 37 38.97 118 53.51  5.88 28   .11  .3  .4 SMO   2.2
92 DEC 17 1925 32.59 40 19.32 119 58.61  0.02 20 2 .41 2.2 2.0 NEV   2.7
92 DEC 17 1938 33.56 40 18.24 124 32.53 12.12 12 1 .11 1.2  .4 MEN   2.3
92 DEC 17 2317 31.64 36 51.54 121 35.33  6.45 53 1 .15  .3  .4 SJB   2.1
92 DEC 19 1232 59.81 37 37.35 118 51.69  7.61 32   .10  .4  .5 SMO   2.7

92 DEC 19 1755 49.62 36 14.51 120 16.55 12.15 40   .15  .3  .6 COA   2.4
92 DEC 20  126  5.52 36 22.39 120 22.81 14.87 37   .15  .4  .4 COA   2.2
92 DEC 20  545 22.73 37 35.54 118 53.07  4.91 34   .12  .3  .5 MOR   2.9
92 DEC 20  936 44.50 36 25.09 120 59.28  5.72 87   .16  .2  .5 BIT   2.8
92 DEC 20 2105 20.82 37 45.02 122  8.99  5.51 95   .21  .2  .5 HAY   3.6

92 DEC 21  411  5.98 38 49.26 122 48.72  2.47 21   .07  .3  .5 GEY   2.2
92 DEC 21  411 54.28 38 49.33 122 48.75  2.22 20   .09  .3  .5 GEY   2.3
92 DEC 21  412 18.29 38 49.50 122 48.79  0.93 11   .07  .3  .7 GEY   2.7
92 DEC 21  412 20.75 38 47.10 122 51.90  0.75 10   .15  .6 1.4 GEY   2.4
92 DEC 21 2053 51.17 35 42.26 118  5.43  5.88 10   .10  .5 1.6 WWF   2.2

92 DEC 22  446  5.84 40 41.98 123 12.23 32.88 11   .14 1.0 1.5 KLA   2.3
92 DEC 22  812  8.15 38 50.86 122 49.60  3.50 24   .07  .2 1.2 GEY   2.7
92 DEC 22 1407 14.65 39 21.40 120 29.89 21.37 18   .07 1.3 2.3 WAK   2.7
92 DEC 23  943 57.66 36 10.45 118  7.91  9.16 14   .08  .5 1.1 WWF   2.6
92 DEC 23 1221 20.71 37 32.83 118 50.15  6.30 29   .11  .3  .8 MOR   2.1

92 DEC 23 1359 34.07 37 32.81 118 50.18  6.28 33   .11  .3  .8 MOR   2.9
92 DEC 23 2028 32.70 36 49.87 121 33.66  7.07 38   .17  .3  .7 SJB   2.0
92 DEC 23 2036 17.17 38 50.20 122 46.43  1.65 28   .12  .3  .8 GEY   2.8
92 DEC 23 2108 51.68 37 32.89 118 50.19  6.55 30   .13  .4  .9 MOR   2.2
92 DEC 23 2330  3.39 36  6.89 120  6.98 10.49 35   .19  .4  .7 COA   2.3

92 DEC 23 2354 58.94 40 18.56 124 27.65  8.02  9   .05 1.1  .5 MEN   2.4

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
----------------------------------------------------------------------------
DEC 17
091918.3  18.334N 105.435W  33N 5.1 4.9 1.2  83 OFF COAST OF JALISCO, MEXICO
100747.1* 45.090N 141.936E  33N 4.2     1.7  16 HOKKAIDO, JAPAN  REGION
103928.6  25.803N  61.467E  33N 5.8 5.5 1.0 115 SOUTHERN IRAN. 
110956.5  14.145N  91.837W 100G 4.8     0.9  68 GUATEMALA
174312.2  37.394N  68.946E  33N 5.2 4.7 1.0  67 AFGHANISTAN-TAJIKISTAN BORD
REG.
185659.0   8.301S 121.728E  33N 5.6     0.9  35 FLORES REGION, INDONESIA. Felt
                                                (I) at Waingapu, Sumba.

DEC 18
031404.9   6.514S 147.245E  33N 5.8 6.1 1.1  72 EASTERN NEW GUINEA REG., P.N.G.
        ML 6.1 (PMG). Some minor damage (VI) at Lae. Felt (III) at Finschhafen
        and Goroka. 

DEC 19
064402.3* 11.282S 166.147E  45D 5.6 5.9 1.0  68 SANTA CRUZ ISLANDS.
093409.4* 45.826N  20.592E  10G 4.3     1.0  22 NORTHWESTERN BALKAN REGION. ML
        4.8 (ROM). Felt (VI) at Timisoara, Romania.
121422.9  51.952N 158.582E  57D 6.1     0.9 124 NEAR EAST COAST OF KAMCHATKA.
215724.7*  0.016N 123.966E 150G 5.3     0.8  17 MINAHASSA PENINSULA, SULAWESI

DEC 20
000856.4? 18.15 S 175.96 W 263D 4.4     0.7  12 TONGA ISLANDS
035804.0*  8.389S 122.489E  33N 5.1     1.4  17 FLORES REGION, INDONESIA
163847.3  25.420S 179.416E 499D 5.2     0.8  69 SOUTH OF FIJI ISLANDS
205242.3   6.541S 130.382E  33N 6.3 7.0 1.0  55 BANDA SEA. 
        (PPT). Felt in parts of northern Australia. 
210520.3  37.711N 122.148W  10G         0.9  19 CENTRAL CALIFORNIA. ML 3.7
        (BRK), 3.7 (GS). Felt throughout the San Francisco Bay area.

DEC 21
061338.6* 52.356N 179.021E 106* 5.7     1.0  76 RAT ISLANDS, ALEUTIAN ISLANDS
114400.7  34.076N 116.370W   5G         0.9  21 SOUTHERN CALIFORNIA. MD 3.7
133926.2  34.216N 116.760W   5G         0.8  10 SOUTHERN CALIFORNIA. MD 3.3

DEC 22
045421.0*  6.628S 130.462E 108D 5.5     1.1  13 BANDA SEA
105456.4? 51.55 N 178.23 W  40D 4.7     0.8  30 ANDREANOF ISLANDS, ALEUTIAN IS.
                                                Felt on Adak.

DEC 23
022006.0* 19.687S  68.572W 105D 5.2     0.6  64 CHILE-BOLIVIA BORDER REGION.
        Felt (V) at Arica, Cuya, Pozo Almonte, Putre and Tana; (IV) at Iquique;
        (III) at Maria Elena, Chile. Some landslides reported in El Morro,
        Chile.
030045.8*  6.419S 130.588E 105D 5.7     0.9  22 BANDA SEA

DEC 24
000326  Q  2.5  N 126.7  E  33N 5.7     0.6  29 NORTHERN MOLUCCA SEA
003419  Q 15.0  S 173.3  W  70      6.4 0.6  87 SAMOA ISLANDS REGION
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