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+--- Thread: swarm in Salton Sea (/showthread.php?tid=488)
swarm in Salton Sea - Island Chris - 09-27-2016
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
RE: swarm in Salton Sea - Island Chris - 09-27-2016
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
RE: swarm in Salton Sea - Skywise - 09-29-2016
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
RE: swarm in Salton Sea - Skywise - 09-29-2016
http://www.scsn.org/index.php/2016/09/26/09262016-m4-3-event-near-bombay-beach/index.html
https://earthquake.usgs.gov/misc/2016-09-27.php
Info on swarm from SCSN and USGS.
Brian
RE: swarm in Salton Sea - PennyB - 09-30-2016
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!
RE: swarm in Salton Sea - Island Chris - 10-01-2016
Here is the link:
http://losangeles.cbslocal.com/2016/09/30/earthquake-advisory-issued-for-southern-california-after-salton-sea-quake-swarm/
RE: swarm in Salton Sea - PennyB - 10-02-2016
(10-01-2016, 10:59 AM)Island Chris Wrote: Here is the link:
http://losangeles.cbslocal.com/2016/09/30/earthquake-advisory-issued-for-southern-california-after-salton-sea-quake-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!