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1995-01-12
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Seismicity Report for Northern California,
the Nation, and the World for the week of
January 5 - 11, 1994
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
San Francisco Bay Area
It was a fairly quiet week in the Bay Area with most activity centered
along the creeping segment of the San Andreas southeast of San Juan
Bautista. During the seven-day period ending at midnight on Wednesday,
January 11, 1995 the U.S. Geological Survey office in Menlo Park recorded
24 earthquakes of magnitude one (M1) and greater within the San Francisco
Bay area shown in Figure 1. Six were as large as M2.0. This total
compares to 19 earthquakes during the previous seven-day period (December
29 - January 4), three of which were as large as M2.
Five of the larger earthquakes occurred along the creeping segment of
the San Andreas. Four of these were associated with a small cluster of
activity that began early Saturday morning with a M2.8 event that was
followed 30 minutes later by a M3.5 (#2 in figure 1). The M3.5 was felt
locally and is the largest earthquake to occur on this part of the
creeping segment since a M3.6 last October 11.
The East Bay was quiet during the week with only one earthquake as
large as M2, a M2.4 last Friday on the central Calaveras fault about eight
miles northeast of Milpitas (#1/1). The only other notable event was a
M1.8 just west of the Antioch fault two miles southwest of Antioch (#4/1).
Northern & Central California
The week began with a M4.5 aftershock in the Markleeville area last
Thursday afternoon that was felt at South Lake Tahoe and Carson City,
Nevada (#2/2). This is the largest aftershock since a M4.6 last September
19, one week after the M6.0 mainshock shook the area.
Two other M4 earthquakes occurred in the north state, both along the
Mendocino fracture zone. The first of these was a M4.5 that occurred last
Saturday afternoon about 160 miles west of Cape Mendocino (see #4 in
Figure 4). This earthquake was large enough to be felt in coastal areas
but produced no damage. Early Wednesday morning, a M4.1 occurred much
closer to the coast that was sharply felt in Petrolia, Honeydew,
Garberville, and Redway (#1/2). No damage was initially reported though a
few items were knocked off shelves in Ettersburg, about 30 miles southeast
of Cape Mendocino.
Three earthquakes in the Cape Mendocino area appeared to be related to
movement within the underthrusting Gorda Plate. On Sunday night a M2.2
occurred about 24 miles east of Petrolia at a depth of about 27 km (#5/2).
It was followed about three hours later by a M2.4 event seven miles
southwest of Eureka that had a focal depth of about 21 km (#6/2). A
second M2 event followed two days later that had a similar location and
focal depth.
Other earthquakes of note during the week included a M3.0 on the
creeping San Andreas about 17 miles northeast of San Ardo (#3/2), a pair
of M2's beneath the central Sierra Nevada about twelve miles south of
Yosemite Valley (#9/2), and a pair of M2's east of Mono Lake (#7/2).
Long Valley Caldera
A M2.3 quake occurred beneath eastern Mammoth Lakes last Thursday night
(#2/3). It was an aftershock to a M3.2 that occurred in the same location
earlier in the week.
USA Seismicity (January 2 - 11)
Data provided by the National Earthquake Information Center showed
several notable domestic earthquakes outside of California. Western
Washington experienced two, the first a M3.3 east of Centralia, the second
a M2.8 in the Tacoma area (#1/4). Southeastern Texas experienced a M2.7
last Wednesday that was felt in the Hallettsville area (#2/4).
The Planet Earth (January 2 - 11)
Northeastern Japan continued to experience strong aftershocks to the
M7.4 offshore quake that struck the region in late December. The
strongest aftershock during the week was a Mb6.6 last Saturday morning
(#3/5). 21 people were reported injured by falling objects, water lines
ruptured, and train service in the area was interrupted. A smaller M6.0
aftershock followed four hours later but produced to injuries or
significant damage.
Other strong earthquakes on the planet during the week included a Mb5.8
in the southern Philippines that was widely felt in the city of Iligan
(#2/5), a Mb5.6 beneath central Ecuador (#4/5), a Mb5.1 in the Galapagos
Islands region (#5/5), and a Mb5.4 in southern China that was felt
throughout the Gulf of Tonkin and as far away as Hong Kong (#6/5).
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 JAN 5 809 20.58 40 19.77 124 12.95 26.95 12 1 .11 .7 1.2 MEN 1.8
95 JAN 5 912 7.87 37 38.86 118 56.81 6.85 15 .07 .4 .8 SMO 1.7
95 JAN 5 920 50.02 40 22.79 124 28.89 17.19 15 2 .09 .7 .3 MEN 2.7
95 JAN 5 1149 13.84 38 47.44 122 45.35 1.99 9 .02 .3 .6 GEY 1.2
95 JAN 5 1233 36.09 38 48.17 122 46.55 1.16 9 .07 .3 .6 GEY 1.2
95 JAN 5 1234 15.09 38 47.99 122 46.25 1.24 16 .11 .3 .6 GEY 1.8
95 JAN 5 1311 39.56 37 38.82 118 56.83 6.43 12 .05 .5 .9 SMO 1.3
95 JAN 5 1436 8.30 37 33.42 118 51.76 10.95 13 .08 .5 .9 MOR 1.1
95 JAN 5 1626 53.83 38 49.91 122 49.98 1.05 8 .06 .4 .9 GEY 1.1
95 JAN 5 1633 29.15 37 34.68 118 50.51 7.83 26 .09 .3 .5 MOR 2.2
95 JAN 5 1633 49.82 37 34.74 118 50.45 7.39 23 .11 .4 .6 MOR 1.5
95 JAN 5 1703 34.23 37 38.83 118 56.84 6.98 21 1 .11 .4 .6 SMO 1.7
95 JAN 5 2019 17.46 36 45.30 121 24.88 7.56 19 3 .15 .5 .6 SJB 1.0
95 JAN 5 2222 16.70 38 45.50 119 40.46 0.04 16 2 .10 .8 1.3 WAK * 2.4
95 JAN 6 12 2.45 38 46.09 119 43.16 1.06 78 3 .23 .4 1.2 WAK 4.3
95 JAN 6 35 14.43 38 45.12 119 44.03 0.04 20 3 .13 .8 1.5 WAK * 2.5
95 JAN 6 100 26.80 38 45.44 119 43.06 0.06 14 2 .17 1.3 2.8 WAK- 2.7
95 JAN 6 141 27.42 38 45.56 119 42.78 1.76 26 3 .12 .7 3.4 WAK 2.7
95 JAN 6 357 21.01 36 14.73 120 49.25 7.91 72 .28 .4 1.5 BIT 3.2
95 JAN 6 507 18.58 38 44.70 119 43.24 2.94 8 2 .09 .9 9.0 WAK - 2.2
95 JAN 6 524 25.48 36 28.60 121 2.58 3.27 24 .08 .3 .6 BIT 1.9
95 JAN 6 618 17.36 38 45.17 119 42.57 0.22 12 4 .10 1.2 1.9 WAK * 2.2
95 JAN 6 623 33.14 37 38.69 118 56.90 6.88 29 .12 .3 .5 SMO 2.4
95 JAN 6 641 22.38 37 34.64 118 50.53 7.97 26 .10 .4 .6 MOR 1.8
95 JAN 6 720 43.72 38 50.63 122 48.36 1.54 9 .02 .3 .8 GEY 1.5
95 JAN 6 756 21.34 38 50.43 122 48.46 0.02 8 .24 .8 4.2 GEY * 1.1
95 JAN 6 759 33.07 38 50.13 122 47.51 3.92 7 .06 .5 3.9 GEY 1.1
95 JAN 6 918 44.17 38 45.40 119 43.71 0.25 15 1 .11 1.1 2.2 WAK 2.4
95 JAN 6 936 59.33 40 11.72 121 16.08 10.86 14 3 .15 1.0 1.4 ALM 1.4
95 JAN 6 1042 24.86 37 24.43 118 34.17 14.55 21 1 .09 .4 .8 RVL 1.7
95 JAN 6 1104 36.64 38 47.65 122 44.79 2.24 7 .03 .3 .8 GEY 1.1
95 JAN 6 1202 33.92 36 32.15 121 4.85 8.41 16 .05 .3 .7 BVL 1.3
95 JAN 6 1225 21.43 37 34.71 118 50.53 7.50 27 .09 .3 .5 MOR 1.7
95 JAN 6 1323 13.82 38 45.34 119 40.53 8.54 8 1 .24 3.318.2 WAK - 2.3
95 JAN 6 1424 23.52 36 3.89 120 15.15 15.40 14 3 .13 1.0 1.9 COA 1.6
95 JAN 6 1546 27.61 38 47.38 122 45.48 1.98 8 .03 .3 .7 GEY 1.2
95 JAN 6 1609 36.04 36 35.20 121 11.03 4.70 19 .07 .2 .6 PIN 1.4
95 JAN 6 1628 10.83 36 56.48 121 40.82 10.15 59 3 .12 .2 .4 SJB 2.0
95 JAN 6 1719 12.40 37 29.52 118 52.20 9.28 24 .10 .5 .8 MOR 1.6
95 JAN 6 1721 29.27 37 29.60 118 52.19 8.43 28 .10 .4 1.2 MOR 2.1
95 JAN 6 1853 32.89 38 43.38 119 43.95 0.03 20 2 .11 .9 1.7 WAK * 2.5
95 JAN 6 1855 51.33 38 43.13 119 44.64 0.06 18 2 .14 1.1 2.0 WAK * 2.5
95 JAN 6 1955 35.15 38 45.58 119 42.46 1.46 7 .09 3.7 9.8 WAK - 2.2
95 JAN 6 2016 22.54 38 49.26 122 46.58 2.95 7 .02 .3 .7 GEY 1.2
95 JAN