From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Newsgroups: sci.geo.geology,ca.earthquakes
Subject: N. CA, USA, and World Quake Report 12/24-12/30/92
Date: 1 Jan 1993 02:22:04 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 24 - 30, 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 30,
1992 the U.S. Geological Survey office in Menlo Park recorded 22
earthquakes of magnitude one (M1) and greater within the San Francisco Bay
area shown in Figure 1.  Four were as large as M2.0.  This total compares
to 19 earthquakes that were recorded during the previous 7-day period,
three of which were as large as M2. 
    Small earthquakes occurred along several of the better known faults in
the Bay Area.  Two events occurred on the San Andreas fault west of San
Francisco early Christmas morning, the first a M1.7 west of the Golden
Gate (#1 in Fig. 1), the second a M1.9 near Pacifica (#2/1).  The Loma
Prieta segment of the San Andreas also experienced several small
earthquakes, the largest a M2.1 event on Monday afternoon (#4/1). 
Although the creeping segment of the San Andreas was as quiet as it's been
in over a month it still managed a M2.7 early Wednesday morning, the
largest earthquake of the week in the Bay Area (#6/1).  The San Gregorio
also creaked a little, producing a M1.9 beneath northwestern Monterey Bay.
   In the East Bay, activity was normal with small earthquakes along much
of the length of the Calaveras fault, the largest a M2.4 about 7 miles
east of Fremont (#3/1).  A slightly larger earthquake occurred  Tuesday
afternoon in the northern Diablo Range, just southeast of Mt. Lewis
(#5/1).  To the north, a M1.7 occurred near the Concord fault, about 2
miles south-southwest of Concord (#7/1).   
        
Northern California

   The northern San Andreas was exceptionally quiet during the past week,
producing just one M2 in the Cape Mendocino area (#6/2).  A slightly
smaller event occurred along the north Maacacama fault, about 25 miles
northwest of Willits (#7/2).
   In contrast the central San Andreas was somewhat more active than it
has been in recent weeks, producing M3 events on two separate segments of
the fault.  The first of these was a M3.3 on Christmas Eve on the
Parkfield segment of the San Andreas (#2/2).  Parkfield of course is the
site of the nation's first authorized earthquake prediction with a M6
earthquake predicted to occur during a 6 year window that ends this month. 
For a few minutes it looked like earth scientists might be getting their
long-anticipated earthquake just under wire.  However, no earthquakes
followed, nor did other instrumentation in the area show any unusual
measurements.  As the year draws to a close, it appears that the
prediction will fail.
    The second M3 occurred last Saturday along the creeping segment of the
San Andreas about 16 miles southeast of Tres Pinos (#5/2).  While this
part of the fault routinely experiences M2-3 events, it has been about six
months since a M3 occurred in this same area.  A pair of M2 events
occurred  6 miles farther to the southeast the next evening.
    Northern and eastern California also experienced notable seismicity. 
A cluster of earthquakes occurred in the northern Sierra Nevada about 6
miles northeast of Quincy (#3/2).  The activity began Christmas Eve with a
M3.8 earthquake that was felt at Quincy and in the Portola area.  It was
followed within minutes by a M2.3 aftershock.  A second M3 occurred 30
hours later.  
   Later that night a pair of M2 earthquakes occurred beneath the
southeastern flank of Mount Shasta, about 11 miles northeast of Mount
Shasta City (#4/2).   Both events occurred at a depth of about 10-11 km
beneath the volcano.  The USGS catalog shows that earthquakes of this size
are not unusual in this location.
       
Long Valley Caldera
    
   The south moat continued to be the most active area within the caldera. 
In addition to a pair of M2 events south of the airport last Thursday, a
small flurry of events occurred just southeast of Mammoth Lakes on
Wednesday (#3/3).  The activity was capped by a M3.1 earthquake, the
largest earthquake to occur in the caldera since early August.  
 
USA Seismicity

   According to data provided by the National Earthquake Information
Service, the most active area in the lower 48 states was the offshore
region of the Pacific Northwest.  Several M3-4 earthquakes occurred along
the southern end of the Gorda Ridge (#1/4) and a M5.2 occurred along the
Blanco fracture zone (#2/4).  The onshore activity was largely limited to
California where aftershocks of the Landers earthquake continue to
dominate (#4/4).  One notable earthquake did occur in the mid-continent: 
a M3.2 event in the New Madrid Seismic Zone.  This small quake occurred
near Cape Girardeau, Missouri and was felt in the immediate area. 
            
The Planet Earth

    The last week of 1992 saw no large earthquakes anywhere in the world. 
The largest of the several moderate earthquakes that were recorded was a
M5.9 in the central Atlantic ocean (#3/5).  A slightly smaller M5.8 in
Ecuador produced slight damage in the town of Tena and was felt in the
capitol of Quito (#2/5).   A M5.3 occurred in the Virgin Islands area that
was felt on St. Croix, St. John, and St. Thomas as well as in parts of
Puerto Rico (#5/5).  In the western Pacific, moderate earthquakes occurred
in central Honshu, Japan (#4/5), in the New Britain region (#1/5), and in
the Solomon Islands (#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 24  839 50.87 36 31.27 121  5.51  1.66 19   .07  .2 1.1 PIN   2.0
92 DEC 24 1322  5.97 37 37.19 118 51.76  8.12 29   .12  .4  .6 SMO   2.6
92 DEC 24 1350 52.30 37 37.21 118 51.57  8.40 23   .11  .4  .6 SMO   2.0
92 DEC 24 1834 51.96 38  4.48 118 47.73 11.78  8   .08 1.4 3.7 MOL   2.4
92 DEC 24 2159 27.38 36 11.68 120 45.31  7.92 28   .17  .4  .8 BIT   2.0

92 DEC 25  335  6.87 35 56.22 120 29.09 10.22 57   .14  .2  .3 MID   3.3
92 DEC 25  425  9.37 39 57.03 120 49.60 15.02 31   .18 1.0 2.2 WAK   3.8
92 DEC 25  457 21.09 39 57.31 120 49.79  2.51 19   .12 1.010.5 WAK - 2.3
92 DEC 25  850 11.78 41 21.60 122  7.29  9.95 11   .22  .8 2.1 SHA   2.1
92 DEC 25 1536 43.14 41 21.44 122  7.48 11.08 17   .22  .6 1.6 SHA   2.8

92 DEC 26  826 11.63 38 50.39 122 47.75  1.60 18   .08  .3  .7 GEY   2.1
92 DEC 26 1040 15.19 39 57.17 120 49.49 12.64 29   .14  .9 3.0 WAK   3.0
92 DEC 26 2246  2.93 36 35.25 121 10.70  3.96 75   .13  .2  .4 PIN   3.1
92 DEC 27   19 30.37 36 59.94 118 11.50 11.82  7   .07 9.3 2.6 OWV - 2.1
92 DEC 27  947 33.57 39 56.36 120 51.60  4.99 12   .14 1.411.3 WAK - 2.4

92 DEC 27 1753 19.07 37 17.39 118 49.36 24.68 19   .07  .8 1.6 KAI   2.2
92 DEC 28   46  1.79 36 12.71 120 24.79  6.53 21   .11  .3  .6 COA   2.2
92 DEC 28  411 51.28 37 32.13 121 49.93  3.37 68   .14  .2  .6 SUN   2.4
92 DEC 28  437 32.91 40 21.73 124 31.40 15.84  7   .09 2.5  .5 MEN   2.6
92 DEC 28  737 40.14 36 33.27 121  3.50  6.34 47   .17  .3  .7 BVL   2.3

92 DEC 28  953  1.41 36 33.33 121  3.57  6.66 21   .08  .3  .8 BVL   2.1
92 DEC 28 1504  2.67 39  1.53 122 35.44  0.00  9   .26  .8 5.5 BAR * 2.2
92 DEC 28 1950 49.25 36 31.25 121  5.85  4.21 47   .12  .2  .7 PIN   2.6
92 DEC 28 2301 52.16 37 29.73 118 51.47  7.55 32   .10  .4 1.1 MOR   2.5
92 DEC 29   15 47.46 37  8.90 122  0.10 12.72 54   .09  .2  .4 LOM   2.1

92 DEC 29  131  2.88 39 57.35 120 49.23  5.98 13   .10 1.510.0 WAK - 2.5
92 DEC 29 2105  1.90 37 28.98 121 37.71  6.01 76   .12  .2  .5 HAM   2.5
92 DEC 30 1125 47.04 36 49.36 121 33.08  4.34 56   .23  .3  .7 SJB   2.7
92 DEC 30 1342 45.30 39 46.36 123 28.42  5.25 17   .13  .4  .8 MAA   2.3
92 DEC 30 1447 50.33 38  1.81 118 43.68  2.22 18   .13 1.9 6.3 MOL   2.2

92 DEC 30 1959 15.53 37 38.13 118 57.12  7.32 26   .12  .4  .6 SMO   3.1
92 DEC 30 2040 27.34 39 47.20 120 41.28  3.14 21   .17 1.510.2 WAK   2.7
92 DEC 30 2128 48.11 37 38.02 118 57.11  7.23 23   .11  .4  .6 SMO   2.1

         
 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 24
092506.1  35.016N 116.964W   5G         0.6  17 CENTRAL CALIFORNIA. MD 3.3
170849.5* 35.881N  80.875E  33N 4.5 4.6 1.7  17 KASHMIR-XIJANG BORDER REGION
185050.8* 17.020N  99.010W  23D 4.8     0.7  38 GUERRERO, MEXICO
190128.0* 17.344N  99.024W  33N 4.5     0.8  31 GUERRERO, MEXICO
220208.6* 16.030S 177.882E  33N 5.0 4.9 1.0  31 FIJI ISLANDS

DEC 25
042509.2  39.971N 120.858W   5G         0.9  29 NORTHERN CALIFORNIA. MD 3.6
        (GM). Felt at Quincy and in the Portola area.
065751.4* 45.434N 147.936E 156D 4.5     0.4  13 KURIL ISLANDS
090858.5  61.821N 149.590W  33N         0.8  11 SOUTHERN ALASKA. ML 3.6 (AEIC).
105029.7  59.504N 151.280W  10G         0.8  13 KENAI PENINSULA, ALASKA. ML 3.4
        (AEIC). Felt at Homer and Seldovia.
221525.5  33.944N 116.299W   5G         0.5  11 SOUTHERN CALIFORNIA. MD 3.1

DEC 26
060204.2   5.466S 152.775E  50G 5.6 5.7 1.0  67 NEW BRITAIN REGION, P.N.G.
065529.3  13.161N 145.486E  61D 4.7     0.9  22 MARIANA ISLANDS. Felt on Gaum
114450.6  36.255N  71.331E 100G 4.7     0.8  19 AFGHANISTAN-TAJIKISTAN BORD REG.
135825.8? 40.54 N 127.52 W  10G 3.8     1.3  18 OFF COAST OF NORTHERN CALIFORNIA
145133.0* 40.437N 127.331W  10G 4.1     1.3  27 OFF COAST OF NORTHERN CALIFORNIA
145740.3*  0.682S  78.090W  10G 5.8 5.3 0.9  70 ECUADOR. Slight damage at Tena.
                                                Felt (III) at Quito.
192812.3* 31.434S 178.760W  33N 5.3     0.6  25 KERMADEC ISLANDS REGION
195223.4*  0.132S  19.593W  10G 5.6 5.9 0.9  34 CENTRAL MID-ATLANTIC RIDGE
221104.9  43.896N 127.962W  10G 5.2 5.3 1.0  84 OFF COAST OF OREGON
224600.1  36.418N 121.469W   5G         0.9  15 CENTRAL CALIFORNIA. ML 3.1 (GS).

DEC 27
001837.0  34.318N 116.851W   5G         0.9  22 SOUTHERN CALIFORNIA. MD 3.7
101257.4  37.517N  89.652W   5G         0.5   6 CAPE GIRARDEAU, MISSOURI 
        REGION. mbLg 3.2 (GS). Felt in the Cape Girardeau area.
111318.3  40.534N 127.446W  10G 3.9     1.0  33 OFF COAST OF NORTHERN CALIFORNIA
162118.2  38.905N 142.363E  33N 5.5 5.5 0.9  78 NEAR EAST COAST OF HONSHU, JAPAN
214905.2   6.049S 113.052E 611D 5.8     1.0  37 JAWA, INDONESIA

DEC 28
052325.6* 23.888N 121.668E  33N 5.0     0.6  17 TAIWAN
084542.1? 26.16 N  67.38 E  33N 5.0     0.8  17 PAKISTAN
090403.8  63.449N 151.398W  10G         0.8  12 CENTRAL ALASKA. ML 4.0 (PMR).
102322.6  38.956N 142.356E  30D 4.8     0.7  29 NEAR EAST COAST OF HONSHU, JAPAN
103438.5* 38.841N 142.445E  26D 4.8     1.1  27 NEAR EAST COAST OF HONSHU, JAPAN
175120.4  33.847N 116.322W   5G         0.9  14 SOUTHERN CALIFORNIA. MD 3.2
180027.8  33.899N 116.272W   5G         0.9  15 SOUTHERN CALIFORNIA. MD 3.6
192030.3* 19.358N  64.333W  33N 4.7 4.8 0.8  44 VIRGIN ISLANDS. Felt on St.
        Croix, St. John and St. Thomas. Also felt in parts of Puerto Rico.
195248.0* 19.407N  64.383W  33N 5.3 4.9 1.0  54 VIRGIN ISLANDS. Felt on St.
                                                Croix, St. John and St. Thomas.
231933.7* 19.372N  64.339W  33N 4.8 4.7 0.9  35 VIRGIN ISLANDS

DEC 30
062526  Q  7.6  S 158.6  E  50  5.6     0.9  39 SOLOMON ISLANDS

DEC 31
072605  Q 38.9  N 142.5  E  33N 5.5     0.7  56 NEAR EAST COAST OF HONSHU, JAPAN


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.
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