Geodetic Observation and Modeling of the Coseismic and Postseismic Deformations Associated With the 2020 Mw 6.5 Monte Cristo Earthquake

Abstract

The 2020 Mw 6.5 Monte Cristo earthquake occurred in the northeastern Mina deflection of the central Walker Lane Belt (WLB) in Nevada, USA. The Mina deflection represents a typical stepover zone that transfers the dextral slip in the northern Eastern California Shear Zone onto the dextral faults in the central WLB. The Monte Cristo earthquake provides a rare opportunity to investigate the strain accumulation and stress transition mechanisms in the WLB. In this study, ascending and descending Sentinel‐1 images were utilized to generate coseismic and early postseismic deformations associated with this earthquake. Combined with global positioning system measurements, these images were inverted for the coseismic slip and afterslip of the Monte Cristo earthquake. The preferred coseismic slip model suggests that the causative fault is characterized by two fault segments with southward dips of 64° and 79°. The coseismic rupture was dominated by sinistral slip with obvious normal slip components in the western segment of the source fault. The coseismic slip was mainly concentrated in the 3–12 km depth range and decreased at shallower depths, suggesting a moderate amount of shallow coseismic slip deficit. Rapid afterslip was mainly confined to the 0–3 km depth range, largely compensating for the shallow slip deficit caused by the mainshock. The widely distributed normal slips in the northeastern Mina deflection revealed by the Monte Cristo earthquake suggest the transtensional model is more applicable due to its ability to account for the slip transition kinematics in the Mina deflection.

Afterslip From the 2020 M 6.5 Monte Cristo Range, Nevada Earthquake

“…These results indicate that maximum coseismic slip at depth was much higher than surface slip. Our results and those of S. Li et al (2021) show that afterslip does not make up for this shallow slip deficit.…”

“…The afterslip model provides a good fit to the data suggesting that viscoelastic relaxation and poroelastic effects are likely secondary processes that can be ignored to first order (e.g., S. Li et al., 2021).…”

“…Hammond et al (2021) used GPS data to suggest ∼1 m of left-lateral slip on the main fault. Zheng et al (2020) combined InSAR and broadband seismic data to suggest that maximum slip was ∼0.8 m. S. Li et al (2021) suggested ∼1.6 m coseismic and ∼0.3 m afterslip using InSAR and GPS data. In contrast to these results, surface offsets associated with the mainshock reached a maximum left-lateral displacement of ∼20 cm, with up to 10 cm of vertical displacement (Koehler et al, 2021).…”

“…Hence, it probably did not stimulate major stress changes in the lower crust or upper mantle. S. Li et al (2021) modeled poroelastic rebound and viscoelastic relax- ation for this event and showed that both were insignificant. In the models presented below, we thus assume that afterslip on the main fault planes is the only contributor to postseismic motion.…”

Interplay Between Seismic and Aseismic Deformation on the Central Range Fault During the 2013 Mw 6.3 Ruisui Earthquake (Taiwan)

“…Poroelastic rebound is generated by changes in pore pressure in the near-source region due to a dislocation (Peltzer et al, 1996). We calculate the poroelastic deformation following Li et al (2021) protocol for an undrained Poisson's ratio of 0.3. Predicted surface displacements (≤1 mm) are one order of magnitude smaller than near-field transient deformation, therefore poroelastic rebound shows no appreciable contribution to postseismic deformation.…”