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Rupture zone characteristics of the 2010 El Mayor-Cucapah (Mexico) earthquake revealed with differential lidar

Lia J. Lajoie, & Ed Nissen

Published August 24, 2016, SCEC Contribution #6918, 2016 SCEC Annual Meeting Poster #115

Recent geodetic studies of surface deformation in large earthquakes have started to make connections between rupture characteristics and the mechanics, geometry, and material properties of the host faulting. Here, we investigate these relationships for the El Mayor Cucapah earthquake by integrating a rich set of field measurements (Fletcher et al.,2014; Teran et al., 2015) with a unique set of three-dimensional surface displacements derived from pre- and post-event airborne lidar topography (Glennie et al., 2014). First, in ground-rupturing earthquakes, slip estimated at depths of 100s of meters to a few kilometers typically exceeds the magnitude of offsets surveyed along the primary fault trace (the “shallow slip deficit”). We seek to clarify how fault zone structural maturity, width, geometry, variations in near-surface material properties, or combinations of these factors might affect this deficit. To establish the slip deficit on each of an array of rupture segments, we compare offsets surveyed at the principal fault scarp with lidar-derived surface displacements measured short distances (100s of meters) from the scarp, and outside of the damage zone observed in the field, which are a proxy for slip at depth. Our second goal is to resolve a discrepancy between field observations in the northern rupture zone which implicate slip on low-angle, NE-dipping detachment faults, and models based upon space geodetic and seismological data which support only sub-vertical structures. Along most of the fault trace, we find that the vertical throw accommodated across the rupture zone far exceeds the extensional heave, indicating that coseismic faulting at depth is steeply-dipping. However, these relations are reversed along a ~5 km section of the Paso Superior fault, where we our data support earlier field-based inferences of low-angle slip. A third goal is to answer outstanding questions about whether the rupture direction of an earthquake is imprinted upon the pattern of surface deformation it produces. Some theories suggest that faults may have a preferred rupture direction that would preferentially concentrate deformation on the same side of the fault for each earthquake. We address this by projecting the mapped surface trace onto surface offset profiles to assess damage zone asymmetry.

Key Words
earthquake, lidar, surface rupture, shallow slip deficit

Lajoie, L. J., & Nissen, E. (2016, 08). Rupture zone characteristics of the 2010 El Mayor-Cucapah (Mexico) earthquake revealed with differential lidar. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology