New Fault Slip Distribution for the 2010 M_w 7.2 El Mayor Cucapah Earthquake Based on Realistic 3D Finite Element Inversions of Coseismic Displacements Using Space Geodetic Data

Abstract

The April 4, 2010 El Mayor Cucapah (EMC) earthquake struck northeastern Baja California, near the border between California and Mexico. This area is characterized by several transform faults which accommodate the relative motion between the Pacific and North American plates, with the former moving NW at a rate of ∼48-52 mm/yr (Argus et al., 2010; DeMets et al., 2010) with respect to the latter. As pointed out by Fletcher et al. (2014), multifault ruptures in the area are the result of different mechanisms including restraining bend tectonics, gravitational potential energy gradients, three-dimensional strain of the transtensional and transpressional shear regimes. The EMC epicenter was located at Long. = −115.27° and Lat. = 32.30°, according to the Southern California Seismic Network (SCSN) catalog. With M w = 7.2 (https://www.globalcmt.org), this is one of the larger seismic events (M w > 6) that has occurred in the area since 1987 (Gonzalez-Ortega et al., 2018; Spinler et al., 2015). Its occurrence caused damage to roads, buildings, and power lines in the city of Mexicali, with extensive damage also reported throughout agricultural areas (Stenner et al., 2010). A comprehensive report has been released by Meneses et al. (2010) (EERI Report No. 2010-02). The EMC earthquake is peculiar for two main reasons: (1) it was characterized by a bidirectional rupture extending more than 120 km along strike and oriented NW-SE; (2) radar interferometry, seismicity, field measurements, and creepmeters (Fletcher et al., 2014; Gonzalez-Ortega et al., 2014; Hauksson et al., 2011) reveal that this event activated more fault segments than any other

3‐D Magnetic Unstructured Inversion

“…Generally, two classes of sophisticated numerical modeling methods can be used with an unstructured tetrahedral model: the FVM (Eymard et al., 2000) and the finite element method (FEM) (Coggon, 1971). The structured FVM scheme has already been used in magnetic field techniques (Lelièvre & Oldenburg, 2006) and other geophysical methods, such as EM (Gündoğdu & Candansayar, 2018; Ishizu et al., 2019; Samrock et al., 2018) and seismic methods (Pulvirenti et al., 2020; Yoshida et al., 2012; Zhong et al., 2014). For problems involving geophysical potential fields, Farquharson and Mosher (2009) developed a gravity data numerical forward modeling method based on the FVM with a structured orthogonal grid, whereas Jahandari and Farquharson (2013) solved the gravity field forward modeling problem by using the FVM and FEM with an unstructured tetrahedral grid.…”