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ML 4.0 (NCSN), Mw 4.3 (UCBSL)

6.8 km (4.2 miles)

Second quake in a week rattles North Coast of California

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December 14, 2001

It was last Friday morning when a M4.4 earthquake shook the Northern California Coast Range. Now, a week later and nearly to the hour, a second magnitude M4 quake shook the region. This morning's earthquake measured a local magnitude (Ml) of 4.0 (NCSN), moment magnitude (Mw) of 4.3 (UCBSL) and was centered in nearly the same location as last week's temblor, but six days and some 20 hours later.

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According to the Northern California Seismic Network (NCSN) the earthquake occurred at 09:41 GMT or 1:41 a.m., December 14, about 9 miles southeast of Ukiah and about 3 miles north of Hopland along the western flank of the Mayacmas Mountains in the Russian River valley. See a Topozone topographic map or a MapQuest street map. The actual location is 1.2 miles east of the intersection of Highway 101 and Henry Station Road, just up the hill from the Parsons Creek Bridge on East Side Road.

The UC Berkeley Seismological Laboratory's (UCBSL) fault plane solution indicated strike-slip motion along a northwest trending plane. See solution. Their moment magnitude (Mw) analysis is slightly higher than the NCSN local (Richter) magnitude. Further analysis may bring these two results closer together.

The quake occurred along the Ukiah segment of the Maacama fault zone.

The earthquake jarred many people from sleep, yet many still slept through it. Those wakened reported a sharp jolt followed by a rolling sensation. Walls shook, pictures rattled, and windows and glassware jiggled. Apparently, nothing toppled from tables or shelves and nobody was injured. Did you feel this quake?

Some people were frightened and had trouble sleeping the rest of the night. We received no reports of spooked animals.

There have been a couple light aftershocks registering in the M1 range.

Additional seismic information links:

Mainstream media news reports:
  • None at this time.
Report update: 2:13:01 PM, Friday, December 14, 2001

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