[Skywise]

Very vigorous swarm going on. As I write this (2:30AM Pacific) there are over 500 quakes in last 24 hours. M3.8 is the largest so far. Depths are mostly 4-7km. It's definitely in the caldera and appears to be in the resurgent dome as well.

I did a quick search on the area for all of 1980. There were nearly 800 events over the entire year but it should be noted that the smallest are about M3 since the instrumentation wasn't as dense or sensitive back then. This swarm has events measured down to the M0 range.

If I limit the current event to M2.5 and above, there are only 34 in the past 24 hours, which roughly puts in comparable to the 1980 sequence.

There was a M6.1 on May 25th, 1980 preceded by months of lower level activity. I think there's a good chance we could see some 4's and maybe at least a 5 in the current sequence.

Brian

[Island Chris]

Brian, if it is a dike injection, like (I think) some of the 1980s were, you may see it getting shallower; let us know. I was at Long Valley in 1988 on a UCSB field trip with R. Bailey of USGS. Was a cool moment when we were sitting on the top of the hill overlooking a road intersection that at the time was the only escape road from Mammoth Mountain. The quakes got really shallow, and USGS really thought there would be an eruption. Lots of flack (threats?) from Real Estate interests. USGS may have moved their office from Bishop to Nevada because they thought there would be a big eruption. Or, this last may not be true.

I did a long reply to your reply below and accidentally deleted it; did not feel like retyping it...
Chris

[PennyB]

[quote='Skywise' pid='435' dateline='1411723927']
Very vigorous swarm going on. As I write this (2:30AM Pacific) there are over 500 quakes in last 24 hours. M3.8 is the largest so far. Depths are mostly 4-7km. It's definitely in the caldera and appears to be in the resurgent dome as well.

I did a quick search on the area for all of 1980. There were nearly 800 events over the entire year but it should be noted that the smallest are about M3 since the instrumentation wasn't as dense or sensitive back then. This swarm has events measured down to the M0 range.

If I limit the current event to M2.5 and above, there are only 34 in the past 24 hours, which roughly puts in comparable to the 1980 sequence.

There was a M6.1 on May 25th, 1980 preceded by months of lower level activity. I think there's a good chance we could see some 4's and maybe at least a 5 in the current sequen
END QUOTE

I note that the sequence is about 10-11 km depth, with one about 6 km. So far no shallowing, but who knows? Bears watching.

[PennyB]

I note that the sequence is about 10-11 km depth, with one about 6 km. So far no shallowing, but who knows? Bears watching.
[/quote]

Looking at today's data...looks as if 4 km are occurring. Just updating.

[Skywise]

(09-26-2014, 10:53 AM)Island Chris Wrote: Brian, if it is a dike injection, like (I think) some of the 1980s were, you may see it getting shallower; let us know.

I just graphed all the quakes in the immediate area since the beginning of the month - 939 events. If there is any trend, it's towards deeper, but the slope is very shallow.

Attached is the graph. The X axis is simply quake number, so does not reflect events properly spaced as they happen over time. Y axis is depth in km.

(09-26-2014, 10:53 AM)Island Chris Wrote: I did a long reply to your reply below and accidentally deleted it; did not feel like retyping it...

Hate it when that happens.

Brian

[Skywise]

LA Time article:

http://www.latimes.com/local/lanow/la-me...story.html

Current thinking seems to be geothermal.

BTW, the picture is a bit deceiving to those who don't know how big the caldera is. It gives the impression that the caldera is just a funky shaped cinder cone.

Brian

[Skywise]

http://volcanoes.usgs.gov/observatories/...chive.html

Looks like things are settling down.

Brian