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Widely Distributed Rupture Along an Array of Left-Lateral, Normal and Right-Lateral Faults in the 15 May 2020 M6.5 Monte Cristo Range, NV Earthquake

Session: Intermountain West Earthquakes in the Spring of 2020 II

Type: Oral

Date: 4/20/2021

Presentation Time: 05:45 PM Pacific

Description: 

On May 15, 2020 a M6.5 earthquake ruptured a collection of shallow faults in the Monte Cristo Range and Candelaria Hills of western Nevada. To identify how this event ruptured through a disorganized fault system, we conducted detailed field mapping at up to centimeter resolution and satellite InSAR analysis at ~15 m resolution of the coseismic surface ruptures, revealing a network of wide, pervasively fractured fault zones with highly varied orientations and kinematics that discontinuously spans the entire 30 km east-west alignment of aftershocks. The coseismic faulting accommodated east-west left-lateral shear where the plate-boundary parallel dextral shear zone of the Walker Lane steps rightward in the Mina Deflection. While seismological and far-field geodetic evidence indicate that the main slip at depth was along an east-striking left-lateral fault plane—a projection of the previously mapped Candelaria fault—our results reveal that shallow slip occurred along a set of north-south oblique right-extensional faults, and along a previously unmapped pair of left-extensional faults that splay 7 – 9 km at 060° strike from the main left-lateral fault on which the mainshock initiated. In addition to resolving the shallow structures involved in this earthquake, our comparison of field mapping and displacement maps derived from InSAR shows the km-wide distribution of surface strain that leads to surface rupture both on and off of the projected main faults. Our results suggest that both field mapping and satellite strain-mapping are required to fully interpret the other; in particular the distinction of primary versus secondary ruptures as in probabilistic fault displacement hazard analyses requires full imaging of the displacement field for these low-offset ruptures; and that this rupture in the Mina Deflection accommodated left-lateral shear in part via coherent right-lateral slip along high-angle conjugate faults in the upper few kilometers of the crust.

Presenting Author: Austin J. Elliott

Student Presenter: No

Authors