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Refining the shallow slip deficit

Xu, Xiaohua and Tong, Xiaopeng and Sandwell, David T. and Milliner, Christopher W. D. and Dolan, James F. and Hollingsworth, James and Leprince, Sébastien and Ayoub, François (2016) Refining the shallow slip deficit. Geophysical Journal International, 204 (3). pp. 1843-1862. ISSN 0956-540X.

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Geodetic slip inversions for three major (M_w > 7) strike-slip earthquakes (1992 Landers, 1999 Hector Mine and 2010 El Mayor–Cucapah) show a 15–60 per cent reduction in slip near the surface (depth < 2 km) relative to the slip at deeper depths (4–6 km). This significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit (SSD). The large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes. One potential explanation for the SSD is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated. In this study, we improve the static coseismic slip inversion for these three earthquakes, especially at shallow depths, by: (1) including data capturing the near-fault deformation from optical imagery and SAR azimuth offsets; (2) refining the interferometric synthetic aperture radar processing with non-boxcar phase filtering, model-dependent range corrections, more complete phase unwrapping by SNAPHU (Statistical Non-linear Approach for Phase Unwrapping) assuming a maximum discontinuity and an on-fault correlation mask; (3) using more detailed, geologically constrained fault geometries and (4) incorporating additional campaign global positioning system (GPS) data. The refined slip models result in much smaller SSDs of 3–19 per cent. We suspect that the remaining minor SSD for these earthquakes likely reflects a combination of our elastic model's inability to fully account for near-surface deformation, which will render our estimates of shallow slip minima, and potentially small amounts of interseismic fault creep or triggered slip, which could ‘make up’ a small percentages of the coseismic SSD during the interseismic period. Our results indicate that it is imperative that slip inversions include accurate measurements of near-fault surface deformation to reliably constrain spatial patterns of slip during major strike-slip earthquakes.

Item Type:Article
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URLURL TypeDescription Information
Hollingsworth, James0000-0003-0122-296X
Leprince, Sébastien0000-0003-4555-8975
Ayoub, François0000-0002-7389-8400
Additional Information:© 2016 The Authors. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2015 December 31. Received 2015 December 30; in original form 2015 June 23. We thank the two reviewers for their valuable suggestions. This study was funded by the U.S. National Science Foundation (EAR-1147435 [DS] and EAR-1147436 [JD]) and the Southern California Earthquake Center (SCEC). SCEC is funded by the NSF Cooperative Agreement EAR-1033462 and USGS Cooperative Agreement G12AC20038. Optical data and fault trace maps were provided by the USGS and CICESE. ERS and ENVISAT data were provided by ESA and were obtained from the WInSAR archive. ALOS data were provided by JAXA and were acquired from ASF archive. GPS data were provided by UNAVCO and CICESE. We thank all of these facilities for their help on this study. The SCEC contribution number for this paper is 2076.
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Subject Keywords:Satellite geodesy; Seismic cycle; Radar interferometry
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Other Numbering System NameOther Numbering System ID
Southern California Earthquake Center (SCEC)2076
Issue or Number:3
Record Number:CaltechAUTHORS:20160509-144838056
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66783
Deposited By: Tony Diaz
Deposited On:09 May 2016 22:36
Last Modified:13 Dec 2019 02:38

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