Special Reports
Regional Location:

Preliminary Magnitude:

Greenwich Mean Date:
Greenwich Mean Time:
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M 4.2 (NCSN)

1.1 km (0.7 miles)

M 4.2 quake jolts The Geysers

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Foreshocks and aftershocks
Earthquake activity is common in The Geysers since steam has been mined since the late 1970s. The US Geological Survey routinely records between 20 and 140 earthquakes per week at The Geysers, so describing what are foreshocks and aftershocks is rather presumptious.

One way to separate the activity is to see where earthquakes have occurred very close to the main shock. For this recent M 4.2 earthquake, there may have been two foreshocks registering M 2.9 and and M 1.4 the previous day. Approximately 11 aftershocks have been recorded, inclusinf a M 3.4 that occurred at about 7 a.m. on Wednesday, May 21.

Felt Earthquake Reports
Shaking from the earthquake was felt as far away as Calistoga and Kelseyville. There have ben no reports from local residents at Anderson Springs or Cobb Mountain.

More information will be added shortly...

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Report update: 8:27:00 AM, Wednesday, May 21, 2003
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