RAPID: Sparta Earthquake Surface Deformation Characterization

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This project will combine geoscience methods to characterize the movement of the landscape associated with the magnitude 5.1 earthquake that shook the town of Sparta in North Carolina on August 9, 2020. These methods will include flying across the area undertaking a high-resolution laser imaging detection and ranging system (LiDAR) to obtain a post-earthquake landscape survey with high vertical accuracy. Surface geology and geophysical observations will be integrated with LiDAR, allowing the precise location and measurement of effects caused at or near the surface by the earthquake. The information gained from this project will be crucial for earthquake hazard analysis and may be applied to reduce failure of building infrastructure and lifelines and loss of life in future earthquakes. Outreach activities with the local communities will be undertaken to broaden understanding of geoscience and specifically earthquakes. The Principal investigators and co-investigators will collaborate with the U.S. Geological Survey and the North Carolina Geological Survey to integrate the results of this study with their efforts. The project is led by a female early career scientist, and diverse graduate students (female, Latinx and African-Caribbean) will gain broad knowledge and experience from working on this project. The Mw 5.1 08/09/2020 earthquake, near Sparta, North Carolina was strongly felt in the town of Sparta (Intensity VI) and across the Southeastern, Midwest, and Northeastern USA, with MMI–II recorded as far away as Wilmington (NC), Atlanta (GA), Cincinnati (OH) and Washington DC. This uncommon moderate earthquake caused a displacement (rupture) of the ground surface, being the first time that a surface rupture was recognized in the eastern USA, after European occupation. Moreover, it is extremely rare for M5 earthquakes to rupture the surface. Efforts to document its characteristics were undertaken on August 9 and the weeks following. Preliminary observations suggest that the surface deformation may be associated to re-activation of sub-surface pre-existent discontinuities, whose tectonic activity is poorly understood. The surface fault is expressed by a narrow zone of deformation, traceable for approximately 2.2 kilometers along strike. Along the length of the surface rupture, the deformation is accommodated by reverse displacement and/or folding/flexure generating a scarp with a maximum vertical displacement of approximately 20 centimeters and average of 8–10 centimeters. This project will complete the characterization of the surface rupture on its entire length. The propject will acquire a high-resolution LiDAR data, and will continue the ongoing acquisition of terrestrial LiDAR scan survey data, high resolution aerial imagery, and subsurface geophysical survey data. Additional geologic and geomorphic observations will be collected, namely through geological excavations that will target areas with potential record for paleoseismicity. This cross-correlation of data will help answer fundamental questions on the Sparta earthquake dynamics. This project will make a strong contribution to the knowledge about seismic risk associated to moderate seismicity in the Eastern United States and very likely for similar intraplate settings. This research will provide the opportunity of understanding how deformation in the surface was accommodated, how the surface rupture occurred and what pre-existing structures near the surface are capable to propagate seismicity. For that, the combination of remote data and field observations which will include sub-surface surveys will be essential. Several studies of seismicity Mw≥6.0 correlating geological deformation, sub-surface structures, paleoseismology, seismology and remote sensing have been undertaken in other regions of the world; however not for a Mw 5.1 and as such this helps make this study unique.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.