The Owens Valley is an extensional regime, but the predominant focal mechanisms are strike-slip. This earthquake is also strike slip with planes striking northwest and northeast. The aftershocks strike northeast, suggesting that the causative fault is left-lateral strike-slip on the northeast-striking plane
As of 2:30 p.m. on Friday March 6, SCSN/TriNet (the Southern California
Seismic Network componenet of TriNet) had recorded 164 aftershocks to this
earthquake. The largest 3 are M4.8 at 9:49, M4.6 at 9:54 p.m., and M4.5
at 11:36 p.m. The aftershocks are decaying as we usually see for aftershock
sequences. At the present rate, the probablity of another earthquake of
magnitude 5 or larger in the next week is about 1 in 8.
As of 2:30 pm, SCSN/TriNet has recorded 495 earthquakes in the Coso
sequence. A second magnitude 5+ earthquake (M5.1) did occur, at 4:36
pm PST on Friday March 6. The sequence is decaying as expected.
The number of M1.5 and greater earthquakes recorded by SCSN/TriNet increased
after each M5+ event and decayed approximately as 1/t. In the first
few hours after each M5, the rate of earthquakes is high enough that not
all of the smaller earthqukaes can be seen.
The spatial distribution of earthquakes indicates a northeast-striking fault with a slight dip to the northeast. This is consistent with the focal mechansims of the earthquakes.