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Photos of faulting from the GNS:
http://www.geonet.org.nz/news/sep-2010-darfield-earthquake/gns-science-response.html
El Mayor - Cucapah Science Coordination Meeting
Date: 15 September (Wed.)
Time: 1:00 - 5:00 p.m.
Location: Main meeting room at SCEC Annual Meeting location, Palm Springs, CA
CICESE colleagues will meet in an open forum with the SCEC community to review status and plans for ongoing studies of the El Mayor - Cucapah earthquake. For each main topic area of seismology, geology and geodesy, there will be an overview of the status of studies conducted so far, followed by discussion on remaining scientific priorities, planning and coordination for upcoming research. Approximately one hour will be devoted to each topic area (with time at the beginning for an overview, and at the end for general discussion). The objective is to further develop and to extend the successful collaboration and cooperation that has already led to many insights about this important earthquake, to ensure that crucial data continue to be acquired, and to help coordinate on joint efforts such as upcoming SCEC proposals. If you are actively engaged in research on this earthquake, or planning to study it, please plan to participate.
Ken Hudnut, USGS Southern California Regional Coordinator; (626)583-7232, hudnut@usgs.gov
For some reason, ESA did not acquire the part of Envisat track A077 that would have covered the quake on July 11. It looks like they did acquire Envisat track D127 on July 14 that should cover the area.
++Eric
Thanks, Robert. I am glad someone was able to get in there and look around a little. I look forward to seeing your data, negative as it may be.
-- Jerry Treiman, California Geological Survey
Hello Treiman,
I made it to the epicentral region today with a ranger escort. I went to the epicenter and to a few locations along the Coyote Creek segment that have been previously mapped, and could not locate any surface rupture where I looked. I did see a lot of locations where fresh small landslides and rockfall occurred, which the ranger also stated were fresh features. The temps there today were around 112-114 and just brutal. I can give you more specifics tomorrow and share some photos and GPS points. Robert LeeperGareth - was that your group that went up Coyote Canyon today? I understand two people were escorted into the closed area to look for fault rupture and I would like to know who they may have been, where they looked and what they saw.
Emails should now be received when follow-up comments are posted if email notification is enabled.
The exact location of the Anza Gap varies a bit depending on which reference you look at, but it seems to be roughly bounded to the north by the 1899 M6.4 (33.667 -116.833) and the 1918 M6.8 San Jacinto earthquakes (33.75 -116.833) and to the south by the 1980 M5 earthquake (33.475 -116.50) (e.g. Sanders and Kanamori, 1984).
The 2010/07/07 M5.4 event was located at 33.420 -116.489, just south of the 1980 event. I am attaching a Google earth plot of showing a rough Anza gap location (blue line) with the epicenter of the recent M5.4 earthquake (red star) and Figure 3 from Sanders and Kanamori JGR 1984.
The CME group is producing an extended source description for this event using the broadband platform source generator. We will post a URL to the SRF as soon as it is ready.
Mike – do you have any contact info for the park staff? Apparently the visitor’s center is only open on weekends and holidays at this time of year. It would help to have some discussions with them in readiness for any further seismic activity.
The Anza Borrego S.P. staff can help with getting special access to the canyon, should it prove necessary. My student, Kim, has done this in the past and is on good terms with the park staff.
-Mike
The next pass of Envisat on July 11 (ascending track 77) is already planned for acquisition. Not sure how quickly we can get the data, but should be better than last month when we had 2-3 week delays. The shorter wavelength of Envisat (5.6 cm) is more sensitive to small motions, and Anza Borrego does not have vegetation.
SCSN moment tensor puts centroid depth at 11 km, so it seems that surface faulting from M5.4 is not likely. With centroid at that depth, we probably won't be able to measure deformation signal at surface from event of this size, but it is worth a look.
After spending some quality time with Google Earth and reading various trail guides I find myself to be less enthusiastic about trying to get into the epicentral area on the chance that there might be surface rupture. The roads into Coyote Creek are all closed in the summer and it is a long hike from any access points that I could see. I have not been in this area before and welcome any comments from those with first-hand experience.
My recent experience in the Yuha Desert has given me great confidence in the ability of the INSAR imagery to highlight surface displacement and I am inclined to wait for the next SAR pass to see if there are any likely targets.
Anyone have fairly precise coordinates for the "Anza Gap"? Any comments on how the July 7 event would affect the interpretation of the AG?
I should think we will have quite a job getting to the GPS sites close to the epicenter. But if we see anything, we'll be sure to record it.
First-Motion Focal Mechanism:
- http://pasadena.wr.usgs.gov/recenteqs/QuakeAddons/ci10736069.cifm1.html
SCSN Moment Tensor Solution:
- http://www.data.scec.org/MomentTensor/solutions/web_10736069/ci10736069_...
Looks like the epicenter is up in Coyote Creek canyon, south of a location known as Bailey's cabin (accessible from the north) and north of Ash Wash (accessible from the south). My understanding is that driving much past either of these locations is forbidden by the park. As Kim Le can attest from her thesis work, it can be quite a hike into the area between these sites.
Attached are hillshades of 0.5 and 1 meter resolution digital elevation model computed (at www.opentopography.org) from the B4 data along the Coyote Creek Fault near the epicenter.
All uploads should be viewable as attachments now.
All uploads are viewed as attachments now. Sorry for the previous mistake in the settings.
Will you be checking fault traces for rupture while you are there?
Here's a message texted to me by Tom Rockwell, who is off-line in B.C. and will be away for the next week:
It looks like the epicenter was near Ash Wash on the Coyote Creek fault. The geomorphology there argues for 1-2 m offsets, so I wouldn't be surprised if we had an M6.9 on the northern Coyote Creek fault. Note: this is one fault that we don't have any paleoseismic information for.
Further caveat: The offset estimate is a seat of the pants feeling as we haven't done the hard work yet. The fault is well-expressed in the field, and the geomorphology "feels" like the displacements are in that range. I was planning on starting the LiDAR assessment this fall. In constrast, the Clark strand has demonstrable offsets in the 3-4m range (see our 2010 SCEC report).
The UAVSAR flight on July 1, which was requested by Andrea Donnellan, I believe includes flight lines as far north as today's quake. I am not sure when it will be possible to fly the lines again.
A Mw 5.4 at 8 km depth might not cause enough surface deformation to map with UAVSAR, unless it ruptured to the surface.
We (UCR) are in the middle of a GPS survey of the San Jacinto fault , as part of a SCEC internship project to measure interseismic deformation. We plan to survey our target sites around Anza tomorrow and perhaps some sites closer to the epicenter (there are several B4 ground control sites) on Friday. We have four useable receivers, currently.
The surface displacements are not likely to be large (and possibly not resolvable), but since we were planning to head down there anyway...