Shallow Fault Slip of the 2020 M 5.1 Sparta, North Carolina, Earthquake

Abstract

Abstract The 2020 M 5.1 Sparta, North Carolina, earthquake is the largest in the eastern United States since the 2011 M 5.8 Mineral, Virginia, earthquake and produced a ∼2.5-km-long surface rupture, unusual for an event of this magnitude. A geological field study conducted soon after the event indicates oblique slip along a east-southeast-trending fault with a consistently observed thrust component. My analysis of regional seismic waveforms, Interferometric Synthetic Aperture Radar, and Global Positioning System survey data yields a compact shallow rupture extending from Earth’s surface down-dip to the southwest over a ∼3 km fault length. The inferred kinematic rupture is primarily toward the up-dip and eastward along-strike directions and has predominantly thrust motion in the west, transitioning to roughly equal thrust and left-lateral strike-slip motion in the east. No normal faulting component, as proposed in an earlier geophysical study, is necessary to explain the data. The prevalence of only dip-slip motions observed at Earth’s surface may demand slip partitioning between dip slip and lateral motions at depth.