SCEC Award Number 15195 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Collaborative Proposal: Fault-Rock Damage structure and Earthquake Hazards in Imperial- Coachella Valley Viewed with Fault-Zone Trapped Waves
Investigator(s)
Name Organization
Yong-Gang Li University of Southern California Rufus Catchings United States Geological Survey Gary Fuis United States Geological Survey Michael Rymer United States Geological Survey
Other Participants
SCEC Priorities 4a, 4b, 4d SCEC Groups Geodesy, FARM, Seismology
Report Due Date 03/15/2016 Date Report Submitted 03/12/2016
Project Abstract
 Through this SCEC’s award, we have completed and are doing the following three aspects of researches for charactering the subsurface rock damage structure of active faults in California using fault-zone trapped waves (FZTWs) in collaboration of USC with USGS researchers:
I. We identified a new type of FZTWs recorded at the dense seismic array atop the Calico fault (CF) in southern California for teleseismic earthquakes, and used these FZTWs to document the deep structure of the CF compliant zone in the upper crust.
II. We imaged the subsurface damage zone of the 2014 M6 South Napa earthquake, California by observations and simulations of FZTWs recorded at the USGS’s dense seismic arrays rapidly deployed across the rupture zone after the mainshock.
The method and experience obtained from I and II are helpful for us to identify FZTWs in the seismograms recorded at other major tectonic faults in California, such as in “The Salton Seismic Imaging Project” (SSIP) in Imperial-Coachella Valleys, and use them to document the subsurface fault-rock damage structure and physical properties.
We received the broadband data recorded at part of stations along SSIP Lines 2, 4 and 5 from IRIS/DMC, which were released by Project PI in mid of January of 2016. We are doing waveform analysis on these data, and still trying to get the complete data recorded at on- and near-fault stations of these SSIP lines from DMC for our systematic examination of FZTWs to imaging the subsurface damage structure of the SAF and major faults in Imperial‐Coachella Valley.
Intellectual Merit Although FZTWs generated by explosions and local earthquakes have been used for characterization of the fault damage structure at shallow depth, it is the first time to identify the FZTWs recorded at the seismic array atop the fault for teleseismic earthquakes and use them to document the deep structure of the fault compliance zone. Because this type of FZTWs arise from seismic waves sub-vertically incident at the fault bottom at deep level, they are more likely to provide unprecedented constraints on the depth extension of fault-zone damage structure where the waves from explosions and local earthquakes can’t approach. This project relates to the SCEC scientific objectives: to develop innovative methods to search for unusual signals using combined seismic, GPS and strong motion data; to investigate near-fault crustal properties and to address how deep the fault LVZ can penetrate into the earth crust. A better knowledge of subsurface fault zone geometry and low-velocity structure will help us to further understand the earthquake physics and quantitatively evaluate the effect of fault-zone waveguide effect on large amplitudes and long duration of ground shaking along the major active faults and related seismic hazard in California.
Broader Impacts Our project is to develop constraints on crustal structure and state of stress for characterization of fault-zone geology, material properties, and their relationship to earthquake rupture processes and triggering. Our results will provide additional information for assessing and mitigating the future earthquake hazards in California: the amplification and localization of strong shaking due to the waveguide trapping efficiency of the low-velocity fault-zones. Our research will be helpful for preparing post-earthquake response strategies for rapid determination of source parameters, maps, dynamic rupture process and other characteristics of the source and ground motion patterns in a major earthquake. The project is parallel to the on-going research at the SAF carried by other SCEC and USGS researchers. We shall provide our interpretation and modeling results from FZTWs for their dynamic rupture modeling during a pending big earthquake in California.
Exemplary Figure none submitted
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