From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Newsgroups: sci.geo.geology,ca.earthquakes
Subject: N. CA, USA, and World Quake Report 1/21-27/93
Date: 29 Jan 1993 01:07:22 GMT
Organization: Stanford Univ. Earth Sciences
Distribution: world
NNTP-Posting-Host: pangea.stanford.edu

NOTE:  TABLE 1 HAS CHANGED SLIGHTLY.  PLEASE SEE THE COMMENT THERE.

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
 January 21 - 27, 1993

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, January 27,
1993 the U.S. Geological Survey office in Menlo Park recorded 20
earthquakes of magnitude one (M1) and greater within the San Francisco Bay
area shown in Figure 1.  Four of these were as large as M2.0.  This total
compares to 32 earthquakes that were recorded during the previous 7-day
period, nine of which were as large as M2. 
  The week began with a M2.0 on the Hayward fault, about 2 miles southeast
of Hayward (#1 in Fig. 1).  This segment has seen occasional M2-3
earthquakes in the past.  
  Four small earthquakes occurred on the San Andreas fault, about 3 miles
southeast of Pacifica (#2/1).  The largest of these was a M1.7 last
Saturday afternoon.   The San Andreas was otherwise largely quiet, with
the exception of one M2.5 on the creeping segment about 5 miles east of
Watsonville (#3/1).
   The central Calaveras fault experienced a pair of M2 earthquakes
Tuesday morning, both located about 10 miles east of San Jose (#4/1).  The
area of last week's M5.0 earthquake was very quiet; only two aftershocks
as large as M1 occurred here during the past seven days.  
  
Northern California

   The northern part of the state was noticeably more active than the
central part, as was the case during the previous week.  M2 earthquakes
occurred throughout the norther Sierra Nevada.  A M2.3 occurred Saturday
about 6 miles east of Quincy (#4/2), site of a M3.2 during the previous
week.  Similarly, a M2.1 occurred Friday  about 15 miles northeast of Red
Bluff (#3/2), the same location as a trio of M2's on Jan. 16 - 19.  In
addition, a M2.2 occurred Thursday about 15 miles southwest of Chester
(#1/2), a M2.1 about 8 miles southeast of Chico (#7/2), and a M2.6 about
19 miles northeast of Portola (#8/2).  
  The Cape Mendocino area was somewhat quieter than the previous week with
only three M2 events near the Cape, the largest a M2.3 along the Mendocino
transform about 41 miles west of Petrolia (#6/2).  The Geysers area
continued more active than normal with a M3.4 early Wednesday morning
(#10/2).
   Other earthquakes of note include a pair of M2's in the Chalfant Valley
area, east of Long Valley caldera (#9/2) and a M3.5 in the southern Sierra
Nevada, about 1 miles northeast of Isabella (#5/2). 
     

Long Valley Caldera
    
    Seismicity was minimal both within the caldera and in the Sierra
Nevada terrane to the south.  During the past week only two earthquakes
occurred in the caldera that were as large as M1.5, both in the south moat
area.  South of the caldera there was only one earthquake as large as M2,
a M2.4 that occurred Wednesday on the Hilton Creek fault (#2/3).  One of
the Chalfant Valley earthquakes, discussed above, is also included in the
area of Figure 3 (#1/3).  
 
USA Seismicity

   According to data from the National Earthquake Information Service
(NEIS), several notable earthquakes occurred in the lower 48 states
outside of California.  The first of these was a M3.6 that occurred last
Thursday in north-central Utah, near the town of Price (#1/4).  Later that
same day a M3.0 occurred in the New Madrid seismic zone, near the town of
New Madrid, Missouri (#2/4).   Tuesday morning a M3.6 occurred beneath
southern Puget Sound, in western Washington State (#3/4).  It was widely
felt in the Puget sound area.
            
The Planet Earth
 
  The most damaging earthquake of the week occurred along the border
region of Myanmar (Burma) and China (#6/5).  At first report this Ms5.7
earthquake injured at least 31 people, destroyed 172 houses, and badly
damaged 1600 homes in the southwestern Yunnan Province, China.  The
northern Myanmar region has experienced at least three M6 earthquakes
during the past year.  Southern Asia was the scene of several other
moderate earthquakes including a pair in the Afghanistan-Tajikistan border
region (#2/5) and a Mb4.5 in western Iran that produced minor damage to
homes in the Abdanan-Dehloran area (#3/5).  
   Other earthquakes of interest include a Ms5.1 on the Alaska Peninsula
that was felt strongly at King Cove and Sand Point (#4/5), a Mb4.8 on the
island of Hawaii that was felt throughout much of the island (#5/5), and a
Ms5.0 beneath the Arctic Ocean, northwest of the New Siberian Islands
(#1/5).  

 Table 1.  Central California Seismicity (M>2.0)

NOTE: the table now includes all earthquakes that are plotted in the California
Figures, not just the ones with Md>=2.  The format is also a bit different than
usual.  If you have a preference let me know.

-ORIGIN TIME (UT)--LAT N-- --LON W--  DEPTH    MAG  N GAP DMIN  RMS  ERH ERZ REG
YRMODA HRMN  SEC DEG  MIN  DEG  MIN     KM     Md  RD DEG  KM   SEC   KM  KM
--------------------------------------------------------------------------------
93 121 1429 28.30 40 10.66 121 28.19  14.12   2.20 16 114 19.0 0.13  0.5  1.5ALM
93 121 1749 25.16 37  5.16 121 27.89   9.43   1.10 11 139  2.0 0.22  1.2  1.8CYS
93 121 1826 44.02 37 38.76 122  2.92   3.47   2.00 35  66  3.0 0.19  0.3  0.8HAY
93 122  257 51.35 38 53.47 119 41.68   1.25   2.50 18 237 95.0 0.19  1.3  4.2WAK
93 122  4 4 57.54 37 37.26 122 26.33  12.76   1.10  7 110  4.0 0.09  1.0  3.4SFP
93 122 1457 18.37 38 47.77 122 44.26   2.88   2.80 38  38  5.0 0.14  0.2  0.7GEY
93 122 20 0 20.46 37 36.84 122 26.14   7.65   1.30 12 116  4.0 0.17  0.9  1.0SFP
93 122 2243 16.92 36 29.83 121  4.20   3.97   2.40 50  52  9.0 0.16  0.2  1.0BIT
93 123  316 10.26 40 22.08 122  6.06  16.58   2.10 15 133 42.0 0.13  1.1  3.4-HA
93 123  332 32.50 37  3.73 121 49.74   6.27   1.10 20  95  2.0 0.06  0.3  0.5LOM
93 123  934 40.75 39 56.80 120 49.56   7.65   2.30 21 225 55.0 0.16  1.0 11.6-AK
93 123 1148 11.85 37  1.86 121 29.50   5.35   1.80 68  64  1.0 0.08  0.1  0.4CYS
93 123 1510  5.62 37 36.91 122 26.05   6.97   1.40 24 112  4.0 0.19  0.4  0.6SFP
93 123 1539 47.67 40 24.53 125  3.27  24.06   2.30 13 276 61.0 0.16  2.8 14.8MEN
93 123 1836 50.35 37 19.48 121 41.42   6.95   1.40 24  67  7.0 0.05  0.2  0.6SFL
93 123 2113 49.76 37 36.86 122 26.24   7.13   1.70 34 117  4.0 0.19  0.4  0.6SFP
93 123 2341 33.66 37  8.64 121 32.19   8.50   1.70 56  69  4.0 0.07  0.2  0.4CYN
93 124  214 49.12 37  8.28 121 32.08   7.05   1.40 35  69  3.0 0.06  0.2  0.4CYN
93 124  726 49.63 38 47.66 123  6.55   4.37   2.20 39  55  2.0 0.18  0.3  0.6PAR
93 124  733 46.27 38 49.95 122 47.66   2.98   2.10 21  53  3.0 0.10  0.3  0.7GEY
93 124  946  5.51 37 12.62 121 35.96   4.52   1.20 19  76  6.0 0.09  0.3  0.9SFL
93 124 1125 35.09 39  7.65 123  3.71   5.54   2.00 24  47  1.0 0.12  0.3  0.5MAA
93 124 1210  6.84 36 54.37 121 38.38   7.43   1.90 69  35  3.0 0.14  0.2  0.4SJB
93 124 1940  4.29 37 25.77 118 53.05   4.62   1.70 28 138 11.0 0.10  0.4  1.3SIL
93 124 21 9 25.97 35 38.52 118 27.30  12.08   3.50 16  74 14.0 0.15  0.4  0.9WWF
93 125  010  8.48 39  7.65 123  3.79   5.79   2.10 24  69  1.0 0.12  0.3  0.6-AA
93 125  3 9 12.64 36 55.01 121 40.09  11.70   2.50 88  48  2.0 0.15  0.2  0.4SJB
93 125  421 58.73 40 43.51 124 11.97   9.35   2.20 13 174 21.0 0.14  0.7  1.3EUR
93 125  523  4.61 37  0.22 121 27.82   8.77   1.20 39  79  3.0 0.09  0.2  0.5CYS
93 125 1814 47.12 40 24.64 124 23.12  11.10   2.20 14 250  8.0 0.14  1.2  0.4MEN
93 126  0 0 41.56 39 44.77 121 40.58  17.65   2.10 10 166 12.0 0.07  0.9  1.1ALM
93 126  030 31.07 37 25.29 118 53.34   3.69   1.80 16 160 12.0 0.07  0.5  1.5SIL
93 126  550 57.72 40  2.21 120 16.85   0.02   2.60 12 279 96.0 0.17  3.1  6.0MOD
93 126  820  4.50 37 34.30 118 52.07   7.27   1.90 15 111  4.0 0.08  0.4  0.8MOR
93 126  851 29.04 37 28.77 118 48.71  10.26   1.70 18 185  7.0 0.06  0.6  1.1MOR
93 126 1149 16.13 38 50.48 122 49.43   4.07   2.20 27  49  5.0 0.14  0.3  0.8GEY
93 126 13 9  7.60 37 21.46 121 43.58   5.88   2.50 86  36  3.0 0.14  0.2  0.4ALU
93 126 1614 59.57 37 20.05 121 42.11   6.52   2.30 82  38  6.0 0.14  0.2  0.5SFL
93 126 18 4  9.54 37 26.30 118 32.49  11.03   2.70 24  78  7.0 0.05  0.3  0.7CHA
93 127  118 54.06 39 22.44 122 52.49   6.60   2.10 12 125 14.0 0.05  0.4  1.8BAR
93 127  6 1  5.97 37 34.42 118 28.69  10.75   2.30 25  86  4.0 0.06  0.3  0.6CHV
93 127  813 36.61 38 49.12 122 46.49   2.81   3.40 41  39  2.0 0.16  0.2  0.5GEY
93 127  815  6.66 38 49.21 122 47.06   2.51   2.80 24  85  8.0 0.15  0.3  1.6GEY
93 127 1028 54.73 37 31.48 118 45.45   6.95   2.40 27  81  9.0 0.10  0.3  1.1WCN
93 127 1122 41.36 37 17.68 121 40.56   2.07   1.40 20  99  4.0 0.04  0.3  0.7SFL
93 127 1625 24.30 36 56.71 121 34.92   8.05   1.60 42  40  1.0 0.24  0.4  0.8SAR
93 127 2333 49.09 38 47.06 122 45.17   0.84   2.30 16  65  4.0 0.11  0.3  1.2GEY
93 128  230  8.95 37 37.38 118 55.86   5.43   1.70 12  94  2.0 0.10  0.5  0.7SMO
93 128  651 53.42 37 37.63 118 52.86   8.93   1.70 11  78  2.0 0.09  0.6  0.7SMO
93 128  719  6.62 37  5.39 122 20.18   8.77   1.30 10 245 12.0 0.14  1.5  1.8ANN

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.
       GAP:  is the largest azimuthal angle without a station in it.
       DMIN: is the distance to the closest station.
       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.
       Md 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.
       REG: is the region name that denotes the velocity model used
            to locate the events.

     
         
 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
-------------------------------------------------------------------------------
JAN 21
090120.4& 39.712N 110.622W   1               22 UTAH. <SLC-P>. ML 3.6 (GS).
091520.6  50.590N 129.699W  10G 4.2     0.9  33 VANCOUVER ISLAND REGION
134312.9  78.885N 125.664E  10G 5.0 5.0 1.2  57 EAST OF SEVERNAYA ZEMLYA, RUSSIA
141529.8* 36.647N  71.065E 100G 5.0     1.1  33 AFGHANISTAN-TAJIKISTAN BORD REG.
        Felt at Islamabad, Peshawar and Rawalpindi, Pakistan.
194619.3& 36.222N  89.617W  14               26 NEW MADRID, MISSOURI  REGION.
        <TEIC>. MD 3.0 (TEIC), 3.0 (SLM). mbLg 3.0 (GS).
201153.8% 38.899N 142.736E  13          1.5  12 NEAR EAST COAST OF HONSHU, JAPAN
210543.9* 38.946N  69.054E  33N 4.5     0.2   7 TAJIKISTAN. Felt (IV) at
                                                Dushanbe, Tajikistan.

JAN 23
041311.0  62.235N 150.240W  82?         0.8  14 CENTRAL ALASKA
085926.0* 24.209N 121.788E  33N 5.3 5.3 1.3  36 TAIWAN
103810.0  33.014N  47.398E  33N 4.5     0.7  20 WESTERN IRAN. Some minor damage
        to houses in the Abdanan-Dehloran area.
172259.4* 18.776S 169.413E 181? 5.2     0.9  52 VANUATU ISLANDS
182214.0  54.611N 161.571W  41* 5.0 5.1 1.4  65 ALASKA PENINSULA. Felt strongly
                                                at King Cove and Sand Point.

JAN 24
210924.9  35.539N 118.463W   5G         0.8  19 CENTRAL CALIFORNIA. ML 3.3 (GS).
                                                MD 3.2 (PAS).
213050.9* 45.917N 142.073E 306D 5.0     0.7  63 HOKKAIDO, JAPAN  REGION

JAN 25
075359.4  55.077N 160.406W  45D 4.8     1.2  25 ALASKA PENINSULA
144609.5* 14.864S 173.888W  33N 5.2 5.5 0.6  50 SAMOA ISLANDS REGION

JAN 26
003937.8* 12.324S 166.377E 250G 4.6     0.5  23 SANTA CRUZ ISLANDS
152408.8& 19.218N 155.482W   9  4.8          48 HAWAII. <HVO-P>. MD 5.0 (HVO).
        Some items knocked from shelves at Pahala and Kailua Kona. Felt
        throughout much of the island of Hawaii as far as Kamuela.
170549.6& 47.368N 122.689W  24               16 WASHINGTON. <SEA-P>. ML 3.6
        (SEA), 3.3 (GS). Felt in the Puget Sound area.
203206.7  22.991N 101.141E  33N 5.4 5.7 0.5  23 MYANMAR-CHINA BORDER REGION. At
        least thirty-one people were injured, 172 houses destroyed and at least
        1,600 houses damaged in southwestern Yunnan Province, China.