Constraints on temporal clustering of earthquakes, Eastern California Shear Zone

Department of Geological Sciences Research

Charlie Rubin, Scott LIndvall, Tom Rockwell

We are currently focusing on the strike-slip faults of the sastern California shear zone (ECSZ). It is an ideal natural l aboratory because of its recent seismicity, accessibility, excellent geologic exposure and availability of high quality seismic and geodetic data. Our goals are to characterize the temporal and spatial record of earthquake occurrence along major faults of the ECSZ. Our research is aimed at collecting paleoseismic data that will (1) enable us to better understand the apparent earthquake clustering observed in the ECSZ from our earlier research, (2) evaluate the repeatability of earthquake ruptures and segmentation within the ECFZ, and (3) assess the discrepancy between geodetic and geologic deformation rates using slip rates inferred from recurrence intervals determined from paleoseismic studies.

Addition Information on our Emerson fault studies.

Images from October field trip

Pinto Mountain fault

	Looking southeast along the Pinto Mountain fault
	Looking east along the Pinto Mountain fault, Scott and Ana for scale
	Looking east along the Pinto Mountain fault
	Potential paleoseismic site View to the south, eastern site
	Pinto Mountain fault scarp View to the south, Ana for scale
	Potential paleoseismic site View to the south, western site
	Pinto Mountain fault Palms trees along fault zone

Blackwater fault

	Folded Pleistocene basalt flow along the Blackwater fault
	Folded and faulted Neogene sandstone along the Blackwater fault

Lenwood fault

	Looking southeast along the Lenwood scarp
	Lenwood fault scarp, Scott and Charlie in discussion
	Looking south

Planning and Schedule

Geologic Mapping
Day 1: Within the next few weeks, Ana with assitance from Lettis & Associates (Scott, Chris or John) and Chris Madden will make a detailed topograhic and Quaternary geologic map along the Pinto Mountain fault. Charlie will provide the total station. The Pinto Mountain fault survey will take one day. They will also discuss our excavation plans with Jane Smith, 29 Palms Inn.

Day 2, The survey team will make a detailed topographic and Quaternary geologic map along the Lenwood fault, southern alluvial fan site. This survey will take one day.

Day 3, The survey team will make a detailed topographic and Quaternary geologic map along the Lenwood fault, central playa site. This survey will take one day.

In addition, during the survey, we will meet with the BLM anthropologist and biologist at the Lenwood site.