Open AccessQuantifying near‐field and off‐fault deformation patterns of the 1992 M w 7.3 L anders earthquake
Author(s) -
Milliner Christopher W. D.,
Dolan James F.,
Hollingsworth James,
Leprince Sebastien,
Ayoub Francois,
Sammis Charles G.
Publication year - 2015
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2014gc005693
Subject(s) - geology , seismology , interferometric synthetic aperture radar , slip (aerodynamics) , deformation (meteorology) , geodesy , geodetic datum , fault (geology) , magnitude (astronomy) , earthquake rupture , displacement (psychology) , synthetic aperture radar , remote sensing , physics , astronomy , thermodynamics , oceanography , psychology , psychotherapist
Coseismic surface deformation in large earthquakes is typically measured using field mapping and with a range of geodetic methods (e.g., InSAR, lidar differencing, and GPS). Current methods, however, either fail to capture patterns of near‐field coseismic surface deformation or lack preevent data. Consequently, the characteristics of off‐fault deformation and the parameters that control it remain poorly understood. We develop a standardized method to fully measure the surface, near‐field, coseismic deformation patterns at high resolution using the COSI‐Corr program by correlating pairs of aerial photographs taken before and after the 1992 M w 7.3 Landers earthquake. COSI‐Corr offers the advantage of measuring displacement across the entire zone of surface deformation and over a wider aperture than that available to field geologists. For the Landers earthquake, our measured displacements are systematically larger than the field measurements, indicating the presence of off‐fault deformation. We show that 46% of the total surface displacement occurred as off‐fault deformation, over a mean deformation width of 154 m. The magnitude and width of off‐fault deformation along the rupture is primarily controlled by the macroscopic structural complexity of the fault system, with a weak correlation with the type of near‐surface materials through which the rupture propagated. Both the magnitude and width of distributed deformation are largest in stepovers, bends, and at the southern termination of the surface rupture. We find that slip along the surface rupture exhibits a consistent degree of variability at all observable length scales and that the slip distribution is self‐affine fractal with dimension of 1.56.