Rapid Geodetic Analysis of Subduction Zone Earthquakes Leveraging a 3‐D Elastic Green's Function Library

Abstract

The 2018 M7.2 Pinotepa earthquake ruptured a shallow slab section along the Middle America subduction zone. We demonstrate how a geodetic Green's function (GF) library and efficient modeling algorithm can rapidly resolve earthquake slip and contribute to early warning systems. The source is characterized with InSAR data and a finite‐element model mimicking realistic slab geometry (Slab1.0) and velocity structures (CRUST2.0) that are not considered in the conventional homogeneous (HOM)‐ or layered(1‐D)‐crust solutions. The rupture is imaged 18 min after geodetic data are downloaded to a 16‐CPU‐thread workstation. Nearby Mw8.6‐megathrust scenarios are also studied with synthetic GPS data in the Guerrero/Oaxaca area. Our results show that earthquake slip solutions are sensitive to the materials of elastic‐modeling domains. Attaining smaller misfits or sums of squared errors, models by 3‐D GFs significantly better recover coseismic displacements than those estimated with 1‐D GFs or HOM GFs at 95% confidence.

Structural Controls Over the 2019 Ridgecrest Earthquake Sequence Investigated by High‐Fidelity Elastic Models of 3D Velocity Structures

“…For instance, the over‐simplification of the 3D elastic domain as a homogeneous or layered half‐space, a conventional practice in coseismic slip inversion exercises, could result in over‐/under‐prediction of slip‐induced displacement when the approximated crust substantially differs from the actual environment. Thus, the resolved fault‐slip distribution and fit to the geodetic observations could be improved by incorporating more realistic lithological configurations into forward models linking fault dislocations to observed surface deformation (Hearn & Bürgmann, 2005; Kyriakopoulos et al., 2013; Tung, Fielding, et al., 2019; Tung, Katzenstein, et al., 2019; Tung & Masterlark, 2016, 2018b; 2018c; Tung, Masterlark, & Lo, 2018; Williams & Wallace, 2015). In addition to modeling the fault kinematics, the near‐fault elastic variabilities should also be considered for accurately calculating the geodetic slip moment (and moment magnitude) and Coulomb stress changes (Das et al., 2019; King et al., 1994; Langenbruch & Shapiro, 2014; Tung, Fielding, et al., 2019; Tung, Katzenstein, et al., 2019).…”

“…Thus, the resolved fault‐slip distribution and fit to the geodetic observations could be improved by incorporating more realistic lithological configurations into forward models linking fault dislocations to observed surface deformation (Hearn & Bürgmann, 2005; Kyriakopoulos et al., 2013; Tung, Fielding, et al., 2019; Tung, Katzenstein, et al., 2019; Tung & Masterlark, 2016, 2018b; 2018c; Tung, Masterlark, & Lo, 2018; Williams & Wallace, 2015). In addition to modeling the fault kinematics, the near‐fault elastic variabilities should also be considered for accurately calculating the geodetic slip moment (and moment magnitude) and Coulomb stress changes (Das et al., 2019; King et al., 1994; Langenbruch & Shapiro, 2014; Tung, Fielding, et al., 2019; Tung, Katzenstein, et al., 2019). Here, we investigate whether more realistic model configurations of rock heterogeneity could improve the earthquake source solutions and their fit to the observed coseismic displacements associated with the Ridgecrest earthquake sequence (Figure 2).…”

“…The left-bottom inlet shows the location of the proximal major faults, namely, the San Andreas Fault and Garlock Fault as well as the Eastern California shear zone and nearby significant events over the past decades. Tung, Fielding, et al, 2019;Tung, Katzenstein, et al, 2019;, 2018b2018c;Tung, Masterlark, & Lo, 2018;Williams & Wallace, 2015). In addition to modeling the fault kinematics, the nearfault elastic variabilities should also be considered for accurately calculating the geodetic slip moment (and moment magnitude) and Coulomb stress changes (Das et al, 2019;King et al, 1994;Langenbruch & Shapiro, 2014;Tung, Fielding, et al, 2019;Tung, Katzenstein, et al, 2019).…”