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Mw 5.0 Olancha Earthquake on 10/1/09 at 03:01 AM PDT
Report by the California Integrated Seismic Network (Caltech/USGS)
Anthony Guarino, Egill Hauksson, Sue Hough, and Bob Dollar
A Mw5.0 mainshock occurred 11 miles northeast of Olancha, in the Eastern Sierra Nevada at 3:01 am (Pacific) on Thursday, 1 October, 2009. The mainshock was preceded by one M1.5 foreshock, and has developed a robust aftershock sequence, with six aftershocks M3.0 and larger, and more than 85 aftershocks within the first 9 hours.
The mainshock was felt across portions of southern and central California, as far away as the Las Vegas, NV area, and as far northwest as the bay area. Strong shaking was reported near the epicenter, in the towns of Lone Pine and Olancha. Due to the remote location of the event, few people experienced the peak instrumental intensity, which was MMI V.
The peak reported intensity from the CIIM reports was MMI V, reported in the town of Independence, approximately 59 km north of the epicenter. Felt reports were distributed similar to the instrumental intensity observed.
CIIM Map for the Mw5.0 Olancha Earthquake, which occurred on 10/1/09
The moment tensor solution displays right-lateral strike-slip motion, on a nodal plane striking N33W. This is consistent with the pattern of aftershocks that have occurred so far. Previous events in this area have been observed historically, with 12 events M5.0 or larger that have occurred in this area since 1933. The largest was the M5.8 Ridgecrest Earthquake, which occurred on 9/20/1995. The most recent M5+ event to occur before this sequence was a M5.2 earthquake, which occurred 7 km ESE of Coso Junction on 07/17/2001..
The moment tensor solution for the M5.0 Olancha earthquake displays right-lateral strike-slip motion, on a nodal plane striking N33W.
Events in this area have spawned robust aftershock sequences in the past, and earthquake swarms for this area are not uncommon. The distribution of events so far may be seen below in the graph, showing other recent significant sequences. This plot is current as of 14:00 UTC.
