Special Reports
Small quake rattles Eastern Sierra near Mammoth Lakes

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October 2, 2001

MAMMOTH LAKES - A small earthquake shook the High Sierra Tuesday morning, but there have been no reports of it being felt.

According to the Northern California Seismic Network (NCSN), the M3.1 temblor occurred about 13 miles east of Mammoth Lakes and 5 miles west of Toms Place and about 2.5 miles southwest of Crowley Lake at the base of Mount Morgan, in the Hilton Creek drainage. (Maps: TopoZone, MapQuest, USGS)

The quake was centered at a depth of 11.3 km (7.0 miles) and probably in the Mount Morgan aftershock zone, a 9-10 km long, northeastern trending belt of tremors caused by a M5.6 earthquake on May 15, 1999. The epicenter, however, plots on the surface trace of the northwest trending Hilton Creek Fault (the same fault that ruptured during a series of four M6 tremors in 1980) but because of its focal depth, it is likely it did not occur along this structure.

Although there have been no reports from the region at this time, it is likely the quake was felt at Crowley Lake and Toms Place. Did you feel this quake? The quake was too weak to topple items from tables of shelves or cause rock slides in the mountains

While residents in the region have felt many tremors in the past, this was the first M3+ quake to occur since May 4 and only the 4th this year. The last M4 quake near Mammoth Lakes occurred on June 3, 1999 - 118 weeks ago!

Earthquake activity at Mammoth Lakes has been rather quiet following the Mount Morgan earthquake in May 1999. Once the robust phase of the aftershock sequence dwindled in the summer of 1999, background seismicity has since hovered in the 10-30 quakes per week range. This past week produced just 12 events. Striking is activity has only once topped the 50 quake per week mark since January 2000.

You can follow weekly earthquake activity in this region with the Seismo-Watch Mammoth Lakes earthquake report. EQ Flash! alert bulletins for California can notify you of M3.0+ earthquakes that occur in the Mammoth Lakes area.

This report was updated at: 11:13:48 AM Friday, October 12, 2001

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