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CD-ROM Aktief 1995 #3
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1995-03-27
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┌─────────────────────────────────────────────────────────────────────────────┐
│▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ California Division of Mines & Geology ONLINE ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒│
└─────────────────────────────────────────────────────────────────────────────┘
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 michael@andreas.wr.usgs.gov
Seismicity Report for Northern California,
the Nation, and the World for the week of
March 15 - 22, 1995
Data and text prepared by
Steve Walter and Barry Hirshorn
U.S. Geological Survey
345 Middlefield Rd. MS-977, Menlo Park, CA 94025
Graphics by Quentin Lindh
NOTE: This report covers an eight-day period from March 15 - 22.
San Francisco Bay Area
During the eight-day period ending at midnight on Wednesday, March 22,
1995 the U.S. Geological Survey office in Menlo Park recorded 18
earthquakes of magnitude one (M1) and greater within the San Francisco Bay
area shown in Figure 1. Five of these were as large as M2.0. This total
compares to 19 earthquakes during the previous six-day period (March 9 -
14) five of which were as large as M2.
A M2.5 earthquake occurred in the East Bay Wednesday evening. The
epicenter was located along the central Hayward fault near the border of
San Leandro and Oakland (#6 in figure 1). It was reported felt by local
residents. This section of the Hayward fault experiences occasional
earthquakes if M2 to M4, most recently a M2.8 last October 28.
The Sargent fault experienced a pair of M2 earthquakes during the week,
the largest a M2.7 last Monday evening (#4/1). Epicenters for both events
were just three miles southwest of Gilroy.
The San Andreas produced two M2 earthquakes on the creeping segment
near San Juan Bautista. The first was a M2.3 that occurred last Thursday
evening about four miles northwest of San Juan (#1/1). It was followed
early Tuesday morning by a M2.0 about seven miles south of the town
(#5/1). The Peninsula segment of the San Andreas experienced a pair of
M1's about seven miles southwest of Los Altos (#3/1) with a M1.5 occurring
just offshore of Pacifica last Saturday night (#2/1).
Northern & Central California
Another quiet week in northern and central California. The Cape
Mendocino area saw just two notable earthquakes: a M3.6 last Thursday
afternoon offshore on the Mendocino fracture zone (#2/2) and a M2.8 Monday
evening six miles west of Petrolia (#7/2). The Coast Range was quiet
except for half a dozen M2's in the Geysers area and a M2.0 about 20 miles
northeast of Calistoga (#8/2).
Central California was nearly as quiet with a trio of M2's on the
creeping San Andreas (#6/2), a pair of small M2's northwest of Coalinga
(#1/2) and one M2.5 one mile southwest of Avenal (#9/2), and one M2.2 ten
miles west of King City (#3/2).
The eastern Sierra Nevada area was actually the most seismically active
area in the state with an active swarm in the Long Valley caldera (see
below) and a pair of M3 events in the northern Chalfant Valley that were
felt in the town of Bishop (#5/2).
Long Valley Caldera
The Long Valley caldera continued to be active for the third straight
week with an active swarm about one mile southwest of the airport (#2/3).
The swarm began Saturday afternoon and continued into the next afternoon.
Nineteen of the earthquakes were as large as M2 including three M3 events,
the largest a M3.5 early Sunday morning. All earthquakes in the swarm had
similar focal depths of ~7 km. This seismicity occurred about three miles
northwest of the pair of M4 earthquake that occurred east of Convict Lake
on March 4.
Activity south of the calderas was limited to four M2 earthquakes that
occurred near Mount Morrison (#1/3).
USA Seismicity (March 12 - 22)
The National Earthquake Information Center reported several notable
earthquakes in the north Rocky Mountain region. Two were in Idaho - a
M2.9 in the Soda Springs area (#2/4) and a M3.5 near the town of Cascade
(#3/4) - and one was in northwestern Colorado - a M4.1 that was felt in
the Dinosaur-Rangely area (#5/4). A Mb4.5 off the west coast of the
Island of Hawaii was felt throughout the island (#4/5).
The Planet Earth (March 12 - 22)
The largest earthquake on the planet was a Ms7.2 along the south coast
of Irian Jaya, Indonesia (#3/5). It was preceded five hours earlier by a
Ms6.3 event. Both earthquakes were widely felt along the south coast of
Irian Jaya though there were no initial reports of damage or casualties.
The world otherwise was relatively quiet with only a couple of small to
moderate earthquakes including a Mb4.9 beneath central Bolivia (#1/5), a
Mb5.3 in northern Xinjian, China (#2/5), and a Mb5.3 in Cook Strait, New
Zealand (#5/5).
Table 1. Northern & Central California Seismicity (M>1.0)
--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
95 MAR 15 1009 17.52 35 51.91 120 56.81 7.49 7 .05 .5 1.3 ROB 1.5
95 MAR 15 1130 48.05 37 34.06 118 50.78 7.07 12 .15 .6 2.3 MOR 2.0
95 MAR 15 1145 35.82 37 34.37 118 50.95 10.18 12 .14 .7 1.7 MOR 2.6
95 MAR 15 1239 52.39 38 50.37 122 48.12 0.02 35 .26 .3 1.6 GEY * 2.5
95 MAR 15 1254 18.40 38 48.25 122 47.94 0.04 9 .05 .3 1.6 GEY * 1.6
95 MAR 15 1927 21.33 38 47.51 122 45.28 0.01 9 .05 .4 1.6 GEY * 1.5
95 MAR 15 2000 5.00 36 17.06 120 27.21 10.59 28 .15 .4 .6 COA 2.1
95 MAR 15 2023 9.30 38 49.17 122 46.82 0.00 8 .13 .4 3.0 GEY * 1.0
95 MAR 15 2259 29.05 36 37.02 121 13.69 4.72 11 .05 .4 1.1 PIN 1.2
95 MAR 15 2356 21.55 36 38.42 121 15.05 10.80 19 .10 .4 1.0 STN 1.4
95 MAR 16 1258 22.30 38 48.38 122 48.70 3.24 7 .02 .3 2.4 GEY 1.0
95 MAR 16 1540 53.42 38 48.16 122 46.13 1.59 7 .04 .3 2.0 GEY 1.1
95 MAR 16 2124 32.54 36 58.39 121 36.94 1.72 11 .21 .6 2.3 SAR 1.0
95 MAR 17 8 46.97 36 19.85 120 54.38 3.71 11 .07 .4 .6 BIT 1.7
95 MAR 17 31 48.74 40 25.79 125 10.51 0.26 28 .36 4.617.1 MEN * 3.6
95 MAR 17 232 24.35 37 35.99 118 50.35 12.30 11 .12 .6 1.1 MOR 1.2
95 MAR 17 334 5.73 36 9.59 120 5.45 6.26 8 .15 1.4 1.1 COA 1.8
95 MAR 17 419 4.89 37 40.92 118 46.42 8.16 8 .01 .6 1.1 EMO 1.6
95 MAR 17 425 29.59 36 51.71 121 35.97 5.96 66 .22 .3 .6 SJB 2.3
95 MAR 17 1336 1.24 38 49.53 122 48.84 0.02 16 .15 .3 1.5 GEY * 1.9
95 MAR 17 2007 10.22 37 14.78 118 32.85 16.93 7 .03 .7 1.3 KAI 1.4
95 MAR 17 2038 25.35 38 46.95 122 45.71 2.10 7 .03 .3 1.4 GEY 1.1
95 MAR 17 2357 35.96 37 37.51 118 51.78 6.54 11 .06 .4 .6 SMO 1.2
95 MAR 18 125 45.96 37 37.48 118 51.99 7