PBO Borehole Strainmeter Recordings of The M6.0 August 24, 2014 South Napa Earthquake
Abstract
A major goal of the Plate Boundary Observatory (PBO) was to enable researchers to study the role aseismic transients play in the earthquake cycle. To attain this goal the Observatory includes 75 borehole tensor strainmeters (BSMs) installed in targeted regions, one being the area to the north and east of San Francisco. The M6.0 August 24, 2014 South Napa earthquake was the largest earthquake in the San Francisco Bay Area in 25 years and provides an excellent opportunity to examine the response of BSMs to a nearby strong earthquake and analyze the temporal evolution of the postseismic shear strains. In this presentation we will document the co and postseismic signals recorded by the two PBO BSMs in the area, one in Lucas Valley, north of San Francisco, at 30 km from the epicenter and the other in the East Bay, 3 km from the Hayward Fault and 40 km from the event. One month after the event the Lucas Valley instrument continues to record a large postseismic signal in the shear strains. We will compare the coseismic offsets as recorded by the BSMs with those predicted using elastic half-space dislocation theory and with those recorded by nearby USGS borehole instruments and characterize the temporal behavior of the postseismic signal at the Lucas Valley strainmeter. UNAVCO operates a network of 1100 GPS sites and 75 BSMs as part of the NSF funded PBO program. For information on the PBO network see http://www.unavco.org/projects/major-projects/pbo/pbo.html , for further information on PBO BSM design, installation techniques and suite of data products see http://www.unavco.org/data/strain-seismic/bsm-data/bsm-data.html.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2014
- Bibcode:
- 2014AGUFM.S33F4906M
- Keywords:
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- 4336 Economic impacts of disasters;
- 7212 Earthquake ground motions and engineering seismology;
- 7215 Earthquake source observations