Fault geometry inversion and slip distribution of the 2010 M_w 7.2 El Mayor‐Cucapah earthquake from geodetic data

Abstract

The 4 April 2010 Mw 7.2 El Mayor‐Cucapah (EMC) earthquake in Baja, California, and Sonora, Mexico, had primarily right‐lateral strike‐slip motion and a minor normal‐slip component. The surface rupture extended about 120 km in a NW‐SE direction, west of the Cerro Prieto fault. Here we use geodetic measurements including near‐ to far‐field GPS, interferometric synthetic aperture radar (InSAR), and subpixel offset measurements of radar and optical images to characterize the fault slip during the EMC event. We use dislocation inversion methods and determine an optimal nine‐segment fault geometry, as well as a subfault slip distribution from the geodetic measurements. With systematic perturbation of the fault dip angles, randomly removing one geodetic data constraint, or different data combinations, we are able to explore the robustness of the inferred slip distribution along fault strike and depth. The model fitting residuals imply contributions of early postseismic deformation to the InSAR measurements as well as lateral heterogeneity in the crustal elastic structure between the Peninsular Ranges and the Salton Trough. We also find that with incorporation of near‐field geodetic data and finer fault patch size, the shallow slip deficit is reduced in the EMC event by reductions in the level of smoothing. These results show that the outcomes of coseismic inversions can vary greatly depending on model parameterization and methodology.

Complex multifault rupture during the 2016 M w 7.8 Kaikōura earthquake, New Zealand

“…We suggest that the earthquake's northward propagation onto numerous faults was the result of static stress changes imposed by the earlier stages of the rupture although dynamic stressing may also have played a role (34). Using only the fault slip from The Humps and Hundalee faults in the south, we calculate positive static stress changes (29) over much of the Upper Kowhai Fault and Jordan Thrust up to ~0.75 MPa (Figure 7).…”

“…This gap coincides with a change from more reverse faulting in the south to predominantly strike slip in the north and is more than double the distance usually assumed as the limit for halting a fault rupture in standard seismic hazard models. The 2010 Mw 7.2 El Mayor-Cucapah in northern Mexico ruptured across a 10 km step-over in the surface faults, but gradients in optical pixel offsets and InSAR data indicated that slip continued at depth (7,34). During the Kaik ura earthquake, slip along the interface could also act as a linking structure at depth.…”

Dynamic Rupture Modeling of the M7.2 2010 El Mayor‐Cucapah Earthquake: Comparison With a Geodetic Model

“…Other works before ours presented estimates of the slip distribution for the El Mayor‐Cucapah event (Fialko et al, ; Gonzalez‐Ortega et al, ; Huang et al, ; S. Wei et al, ). The data sets used to constraint the final slip include teleseismic waveforms, InSAR points, GPS measurements, SPOT images, and/or various combinations of these.…”

“…S. Wei et al () also showed that rupture propagated bilaterally, toward the NW and SE. Models that incorporate geodetic data represent the interface geometry as a concatenation of four to eight faults and with maximum slip between 5 and 6 m (Fialko et al, ; Gonzalez‐Ortega et al, ; Huang et al, ; S. Wei et al, ). They also show that the majority of slip occurred in the northern region of the fault interface.…”

The 2016 M7 Kumamoto, Japan, Earthquake Slip Field Derived From a Joint Inversion of Differential Lidar Topography, Optical Correlation, and InSAR Surface Displacements

“…For the range of regularization values, the lidar-optical-InSAR inversion resolves a greater maximum slip than does the optical-InSAR inversion. Huang et al (2017) observed that the regularization affects the depth profile of slip for the 2010 M7.2 El Mayor-Cucapah earthquake. The moment release migrates from the Hinagu to Futagawa Fault with increasing regularization (Figure 4c).…”