After the extravagance of earthquakes of Ml>=2 in the California (especially central/northern
California) areas, a dead calm has settled on the region. In southern California (SCSN)
there has not been an event of Ml>=2 in two days and only 1 in the past 3 days. Things
are a bit more lively in Central/Northern CA, but not much, with 4 in the past 3 days.
Chris in suburbia (and others) have noted this lack of activity on several occasions
following strong geomagnetic storms and it may be much of the cause of the statistical
increase in activity about 4 days after geomagnetic storms - as a sudden return to
normalcy, rather than a strong increase in seismicity rate at that time. If this continues,
we may have to go into overtime on the SFB contest.
Right now, the areas to watch will probably be volcanics. They usually "heat up"
between 2-5 days after strong geomagnetic storm. Either bubbles are released
during the storm which take 2-5 days to migrate up through magma chambers, increasing
magma chamber pressure as the rise and expand, or some actual heating of the
magma is occurring from Ohmic heating - hard to say, but statistical evidence
suggests whatever the cause, it takes 3-5 days before this effect is seen.
With the Mb 4.0 off the Coast of Oregon today and volcanic tremor north of
Mexico City the volcanic effects may be on the upswing today - I think Petra
who watches those volcanos closely could tell us more about the swarm of
earthquakes at the EJE Volcanic Center north of Mexico City today.
Anyway, areas which typically show some seismic increases, probably
related to underground magma chambers in California include the Mammoth Lakes,
Coso Junction and Calexico regions. Further up north the Cascade volcanics are
often unusually active after a slight delay following geomagnetic storms.
Globally, there is usually a strong eruptive episode including several major volcanic
eruptions 3-7 days after strong geomagnetic storms. Mid-Ocean ridges also
become unusually active at this time.