At 02:41 PM a moderate magnitude 4.0 earthquake with epicenter near Berkeley shook the San Fransisco Bay area. 6 hours later a similar earthquake this time measuring 3.8 hit the same Berkeley area. Both quakes were felt far away from San Fransisco. The earthquakes were felt as far as Portland, Oregon to the north, Sacramento to the east and San Diego to the south. The earthquake occurred almost below a known Hayward Fault line. The earthquake was the largest one in this fault line since several years.
At 08:16 PM another earthquake hit the same Berkeley area. The Hayward fault line was also here the main responsible. The 08:16 quake has to be regarded as an aftershock of the earlier 02:41 earthquake.
Earlier in the day, millions of Californians participated in a statewide earthquake preparedness drill that was sponsored by state and federal emergency response agencies, the American Red Cross and others. (EarthquakeReport)
NCSS Moment Tensor Solution
Waveform data (solid line) and synthetic data (dashed line) from the moment tensor inversion:
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