Breaking the oceanic lithosphere of a subducting slab: The 2013 Khash, Iran earthquake

Abstract

[1] Large intermediate-depth, intraslab normal-faulting earthquakes are a common, dangerous, but poorly understood phenomenon in subduction zones owing to a paucity of near-field geophysical observations. Seismological and high-quality geodetic observations of the 2013 M w 7.7 Khash, Iran earthquake reveal that at least half of the oceanic lithosphere, including the mantle and entire crust, ruptured in a single earthquake, confirming with unprecedented resolution that large earthquakes can nucleate in and rupture through the oceanic mantle. A rupture width of at least 55 km is required to explain both Interferometric Synthetic Aperture Radar observations and teleseismic waveforms, with the majority of slip occurring in the oceanic mantle. Combining our well-constrained earthquake slip distributions with the causative fault orientation and geometry of the local subduction zone, we hypothesize that the Khash earthquake likely occurred as the combined result of slab-bending forces and dehydration of hydrous minerals along a preexisting fault formed prior to subduction.

Geodetic Constraints on the 2014 M 6.0 South Napa Earthquake

“…However, most moderate and large earthquakes do not have such observations available, particularly in a time frame necessary for earthquake response, and earthquake response products have to rely on teleseismic source models that may contain substantial uncertainties with respect to event location, complexity, and spatial extent (Hayes, 2011;Barnhart, Hayes, Briggs, et al, 2014;Barnhart, Hayes, Samsonov, et al, 2014). Furthermore, teleseismic source models may not be suitably constrained for damaging events M w < 7.…”

“…Here, we describe our procedure for deriving a source model for the South Napa earthquake, which is followed for other events analyzed by the NEIC (Barnhart, Hayes, Briggs, et al, 2014;Barnhart, Hayes, Samsonov, et al, 2014;Hayes et al, 2014). Although field observations of fault rupture are available to more precisely constrain fault location, we explicitly do not use these to provide a synopsis of NEIC operations for global events where such observations would not be available, rapidly or otherwise.…”

Seismological and geodetic constraints on the 2011Mw5.3 Trinidad, Colorado earthquake and induced deformation in the Raton Basin

“…The single look direction, the blind nature of the event, and the small magnitude of surface displacements compared to noise in the data potentially lead to an unstable inverse problem where fault plane geometry and dimensions may trade off significantly when attempting to invert for distributed slip [e.g., Devlin et al , ; Scott et al , ]. To address these issues, we generate three candidate slip distributions following the general methodology of Barnhart et al [, ], beginning with inverting for fault geometry and location. We have explicitly chosen to focus on the east dipping focal plane, as this is consistent with both the depth distribution of aftershocks [ Rubinstein et al , ] and previous events in this region [ Meremonte et al , ].…”

Viscous Accretionary Prisms: Viscoelastic Relaxation of the Makran Accretionary Prism Following the 2013 Baluchistan, Pakistan Earthquake

“…The location and sense of slip of the 2013 Baluchistan earthquake is shown in red. The surface topography is exaggerated 2× (Amante & Eakins, 2009), and the subducting slab geometry is from Barnhart, Hayes, Samsonov et al (2014). for the ECPT in the Makran. Davis and Lillie (1994) suggested that this crystal plastic flow could explain the wedge geometry of the Sulaiman fold belt, which is similar to the Makran when accounting for the Makran's slab geometry.…”