[Island Chris]

Am ongoing swarm in Salton Sea near southern San Andreas fault. I know this sort of thing gets the seismologists interested, and maybe a little nervous. There was M4.3 strike slip in the last hour. Of course we have seen swarm activity before in this area not followed by a major quake.
Chris

[Island Chris]

The swarm has at east three M4+ quakes. Those are all strike-slip. There are shallow: just a few km. They are aligned NE-SE and there precision on horizontal location is only 0.2 km. Thus, the zone that is moving a little bit is left-lateral. There are known cross faults, striking at a high angle to the San Andreas fault, in this area. One of these failed in a M6.2 left-lateral earthquake in 1987 (Ellmore Ranch), and that quake triggered the larger (M6.7?) Superstition Hills right-lateral quake within less than a day. I am doing this from memory; not checking online; if you are interested and the detail matters, you may want to check my previous sentence
Chris

[Skywise]

This appears to be on a spreading ridge where the right lateral San Andreas transform fault converts to the East Pacific Rise. There are geothermal features in this area, include geothermal power plants.

On one hand it is concerning that this is the south end of the southern segment of the San Andreas, which has not ruptured in recorded history and appears to be waaaaay overdue based on paleoseismology.

On the other hand, it may be typical for this area if it is in fact spreading related. The moment tensors of the three 4+ events are consistent with spreading.

I'm inclining towards the later and not worrying too much.

Brian

[Skywise]

http://www.scsn.org/index.php/2016/09/26...index.html

https://earthquake.usgs.gov/misc/2016-09-27.php


Info on swarm from SCSN and USGS.

Brian

[PennyB]

The California Office of Emergency Services has issued a one week advisory about potential for a larger quake.  Small probability..but interesting that they issued this!

[Island Chris]

Here is the link:

http://losangeles.cbslocal.com/2016/09/3...ake-swarm/

[PennyB]

(10-01-2016, 10:59 AM)Island Chris Wrote: Here is the link:

http://losangeles.cbslocal.com/2016/09/3...ake-swarm/

I wonder if other data was used.  The swarm and high seismicity in the area is definitely distinct, but have there been well measurements, land elevation changes, etc?  I'm too far gone from the field to know, alas!