For a while this afternoon and evening, it appeared that the aftershock sequence from
the Calexico earthquake had dropped to levels below Ml 3.0. However, a new solar
flare of class C5.0 began a few minutes after 6:00 UT (10:00 PST). This was the
largest flare since the aftershock sequence began and occurred while the aftershock
zone was near antipodal to the sun.
As soon as this flare began - at 0:07 UT the aftershock sequence re-energized with
5 events of Ml>=3 in the next hour and a half. There had been no events of Ml>=3
from about 03:00 PST to 10:00 PST while solar activity was low.
What this suggests is that there is still considerable energy left in this fault system.
A large solar flare in the next day, if it occurs near noon or midnight at Calexico COULD
trigger a second, larger event, perhaps in the Mw 6-7 range.
One thing for sure, it will be an interesting aftershock system to watch, although
because it is occurring in an area of high heat flow, the aftershocks should diminish
rapidly and the immediate aftershock sequence should be nearly over within 2-3 days.
(p in the Omori formula will probably be 1.2-1.3 for this sequence).