Hierarchical interlocked orthogonal faulting in the 2019 Ridgecrest earthquake sequence
A nearly 20-year hiatus in major seismic activity in southern California ended on 4 July 2019 with a sequence of intersecting earthquakes near the city of Ridgecrest, California. This sequence included a foreshock with a moment magnitude (M_w) of 6.4 followed by a M_w 7.1 mainshock nearly 34 hours later. Geodetic, seismic, and seismicity data provided an integrative view of this sequence, which ruptured an unmapped multiscale network of interlaced orthogonal faults. This complex fault geometry persists over the entire seismogenic depth range. The rupture of the mainshock terminated only a few kilometers from the major regional Garlock fault, triggering shallow creep and a substantial earthquake swarm. The repeated occurrence of multifault ruptures, as revealed by modern instrumentation and analysis techniques, poses a formidable challenge in quantifying regional seismic hazards.
Additional Information© 2019 American Association for the Advancement of Science. This is an article distributed under the terms of the Science Journals Default License. Received 5 August 2019; accepted 23 September 2019. The ALOS-2 original data are copyrighted by JAXA and provided under JAXA RA6 PI projects P3278 and P3360. The Copernicus Sentinel-1 data were provided by the European Space Agency (ESA) and contain modified Copernicus data 2019, processed by ESA, Caltech, and NASA/JPL. E.H. received support from USGS/NEHRP grant G19AP00035 and NSF awards EAR-1550704 and EAR-1818582; Z.Z. and Z.J. received support from USGS grant G19AP00030. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794. Author contributions: Z.E.R. performed the template matching and seismicity relocation. E.H. calculated three-dimensional earthquake locations. M.S. and B.I. performed the slip inversion. Z.J., X.W., and Z.Z. performed the subevent modeling. E.J.F. and O.L.S. performed the InSAR data processing. M.Z. determined offset fields for the InSAR data. S.-H.Y. and J.J. produced the DPMs. Z.L. and A.W.M. processed the GPS data. O.L.S. performed the Garlock fault creep analysis and smoothed seismicity plots. All authors contributed to writing the manuscript. Competing interests: A.W.M. is a member of the UNAVCO Geodetic Data Services Advisory Committee. Data and materials availability: All seismic data used are publicly available from the Southern California Earthquake Data Center and the IRIS DMC. GPS data are available from Network of the Americas (NOTA) and UNAVCO. The seismicity catalog produced in this study is publicly available from the Southern California Earthquake Data Center.
Supplemental Material - aaz0109_Ross_SM.pdf