Surface Rupture on a Secondary Fault Associated with the 8 August 2020 Mw 5.1 Sparta North Carolina Earthquake

On 8 August 2020, northwest North Carolina experienced an Mw 5.1 earthquake that caused damage to buildings and roads in the city of Sparta. A regional centroid moment tensor solution shows that the earthquake was the result of slip on a reverse fault with a minor strike-slip component. Interferometric Synthetic Aperture Radar (InSAR) data, from the Japan Aerospace Exploration Agency’s Advanced Land Observing Satellite #2 (ALOS2) satellite, reveal a deformation field that is more complex than expected from a single reverse fault earthquake. The data also reveal an apparent fault rupture at the Earth’s surface that caused damage to local roads. Modeling of the InSAR deformation field indicates the fault rupture is associated with a very shallow normal faulting event with an equivalent Mw of about 5.1 that overprinted the reverse fault deformation field and possibly occurred aseismically.