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+--- Thread: 7.1 (/showthread.php?tid=3168)
7.1 - Skywise - 07-06-2019
I'll just say....wow.
Funny thing is, I was already looking at the maps and a live seismo because i felt the 5.0 just a few minutes before.
Brian
RE: 7.1 - Island Chris - 07-06-2019
As Brian and some of our people who used to post know, this sequence has similarities to the 1987 Ellmore Ranch-Superstition hills pair. Ellmore Ranch was a M6.2 left lateral quake that was followed by about a half day by a M6.7 (?) right-lateral quake. I talked to seismologist Craig Nicholson after the M6.4 and he said the M6.4 July 4 was not that simple. It had a focal mechanism for strike slip. Most of the aftershocks outlined a NE-SW lineament which is the left-lateral plane. But there were also quakes along a shorter NW-SE right lateral plane. Looks like that NW-SE right-lateral motion triggered the M7.1 on the same fault. Hmm, may have to check SCEC and IRIS web sites to see if that was a known, named fault.
Brian, I can post more if you and other smart people post on earth sciences. A lot has happened with me the last 4 years.
Chris
RE: 7.1 - PennyB - 07-07-2019
(07-06-2019, 04:27 PM)Island Chris Wrote: As Brian and some of our people who used to post know, this sequence has similarities to the 1987 Ellmore Ranch-Superstition hills pair. Ellmore Ranch was a M6.2 left lateral quake that was followed by about a half day by a M6.7 (?) right-lateral quake. I talked to seismologist Craig Nicholson after the M6.4 and he said the M6.4 July 4 was not that simple. It had a focal mechanism for strike slip. Most of the aftershocks outlined a NE-SW lineament which is the left-lateral plane. But there were also quakes along a shorter NW-SE right lateral plane. Looks like that NW-SE right-lateral motion triggered the M7.1 on the same fault. Hmm, may have to check SCEC and IRIS web sites to see if that was a known, named fault.
Brian, I can post more if you and other smart people post on earth sciences. A lot has happened with me the last 4 years.
Chris
Hi guys: Just noting that the aftershock sequence is now edging into the area of the Garlock Fault. Might be worth watching?
Penny
RE: 7.1 - Skywise - 07-08-2019
(07-07-2019, 05:56 PM)PennyB Wrote: Hi guys: Just noting that the aftershock sequence is now edging into the area of the Garlock Fault. Might be worth watching?
Penny
I've noticed that too.
Although it's fair to categorize this as a post-diction, I noticed that the aftershocks of the original 6.4 were quite vigorous, with many of the larger aftershocks clustered on the north end of the NW-SE trend. This is where the eventual 7.1 broke.
And now I note that there is a cluster of aftershocks further north again. This is approaching the Owens Valley fault zone. However, it's likely not been long enough since the 1872 Lone Pine quake.
Also of note is what appears to be another SW-NE lineament of aftershocks north of the original SW-NE break from the 6.4 quake. This line on the east has a cluster on the Ash Hills fault.
And of course, as Penny has noted, the 7.1 seems to have broken southward up to the Garlock Fault.
Ross Stein and his group had posted on their temblor.net site a map of the coulomb stress distribution of the 6.4 quake (which I happened to be looking at when the 7.1 hit). Not surprising that the 7.1 occurred in one of the stress lobes.
http://temblor.net/earthquake-insights/southern-california-m-6-4-earthquake-stressed-by-two-large-historic-ruptures-8976/
The article shows how the past Lone Pine and the more recent Landers earthquakes likely influenced the 6.4 event with the stress distributions.
There is also an article on the 7.1, where they discuss the fault also rupturing to the south.
http://temblor.net/earthquake-insights/magnitude-7-1-earthquake-rips-northwest-from-the-m6-4-just-34-hours-later-9041/
Furthermore, there is discussion of the wider implications of this quake series, which has a stress map indicating at least 2 bars of additional stress on the Garlock Fault.
http://temblor.net/earthquake-insights/m-7-1-socal-earthquake-triggers-aftershocks-up-to-100-mi-away-whats-next-9055/
Overall, I think it's worth being prepared. We've been in a 'quake drought' for the past 20 years. Things may be lighting up in the future.
Life has had me busy for the past several years. Lots of changes for me as well. I'm a little behind on my quake studies. Need to read up on these events and faults.
Brian
RE: 7.1 - Island Chris - 07-18-2019
Thanks Brian
interesting. have not clicked on your links yet. Lots of things have changed in my life the last 4 years. Has been a bit rough
Chris
RE: 7.1 - PennyB - 07-18-2019
(07-18-2019, 11:18 PM)Island Chris Wrote: Thanks Brian
interesting. have not clicked on your links yet. Lots of things have changed in my life the last 4 years. Has been a bit rough
Chris
Hang in there! I always look for your good posts here.
Penny
RE: 7.1 - PennyB - 07-20-2019
Interesting...the huge number of aftershocks seems to be stopping at the Garlock Fault to the south. There are a few quakes further west on the Garlock, but nothing to the south. Just interesting.
Penny