Regional Location:

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    		 CENTRAL CALIFORNIA

    ML 4.1 (NCSN), Mw 4.1 (Berkeley)

    01/07/02
    17:33:53
    36.6943N
    121.3328W
    3.6 km

    Seismo-Watch Significant Earthquake Reports- No. 01-020
    More Special Earthquake Reports
    HOLLISTER, CALIFORNIA, JULY 2, 2001 (Seismo-Watch) -- A moderate earthquake measuring ML 4.1 (NCSN), Mw 4.1 (UCBSL) occurred at 17:33:53 UTC (10:33 a.m. local time), July 2, in the hills of Central California south of Hollister, but was too weak to topple any items from tables or shelves.

    Seismo-Watch EQ Flash! Alert Bulletins subscribers received a notification of the earthquake within minutes of the shaking (See a copy of this bulletin). You should subscribe to the service too! It's FREE and Fast!
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    The quake happened on a clear morning and was centered about 12 miles south of Hollister and 15 miles northwest of the Pinnacles National Monument along the back side of the Gabilan Range in Cienega Valley, at the junction of Cienega Valley and Harlin Mountain Roads. See a Topo Zone location map.

    Analysis by U.C. Berkeley determined a Moment magnitude of Mw 4.1 (see moment tensor solution) and their fault plane solution indicated the earthquake was caused by strike-slip motion along a northwest trending fault, suggesting the quake triggered along the San Andreas Fault. See some seismic waveforms below.

    Foreshocks and aftershocks
    Although this portion of the San Andreas Fault receives a number of earthquakes every week, thus being referred to as the "creeping segment", a number of tremors were recorded within a couple hours of the main shock, including one as large as     M3.4 at 10:32:32 a.m. (Felt?)

    Four aftershocks were detected within the first two hours of the main jolt (largest: M2.3 at 10:44:47 a.m. but none were recorded in the subsequent four Hours.

    Felt Reports
    The temblor was widely felt in the region and as far away as the Monterey Bay area (Monterey, Salinas, Santa Cruz), on the San Francisco Peninsula as far north as Mountain View and Stanford, and in the East Bay Area, including Livermore and Pleasanton. Most people have reported a brief shudder of the ground, catching their attention but did not last long enough to cause alarm. There have been no reports of items toppling from tables or shelves.

    Brief Background
    It was the first     M4+ earthquake to strike Central California south of the San Francisco Bay since the Mount Hamilton M4.4 earthquake on February 22 and just the third this year.

    Additional Seismic information links:

    • Seismo-Watch Links to California Activity
    • NCSN Recent Earthquakes Page.
    • USGS Community Intensity Report
    Seismograms of the earthquake series from nearby stations:
    • Fremont Peak (NCSN)
    • Parkfield (NCSN)
    • Stanford (NCSN)
    Mainstream media news reports:
    • None at this time
    Report update: 12:25 p.m. PDT, Tuesday, July 2, 2001
    See a local epicenter map.
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