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Exploring the Relationship Between Subsurface Structure and Seismicity for the Eastern United States

Description: 

The Eastern United States hosts several seismically active regions such as the New Madrid, the Wabash Valley, the South Carolina, the Central Virginia, and the West Quebec seismic zones. It is not clear what factors control the occurrence of these intraplate earthquakes. Previous geodynamic studies have suggested that some intraplate earthquakes may be due to localized stress concentrations. Since subsurface structure heterogeneity can cause stress concentration, we examine the three-dimensional subsurface structure of the Eastern United States to investigate potential relationships between subsurface structure and seismicity. To constrain the subsurface structure, we simultaneously inverted smoothed P-wave receiver functions, Rayleigh-wave phase- and group-velocity measurements, and Bouguer gravity observations. Our velocity model agrees relatively well with previously published seismic models. Comparing the earthquake locations and subsurface structure variations, we found that earthquakes in the Eastern United States often, but not always, locate near regions with seismic velocity variations. However, not all regions of significant subsurface wave velocity changes host detectable seismicity. We also observed a weak correlation between upper mantle shear velocity and earthquake focal mechanism in the Eastern United States. Thrust faulting earthquakes are often located in regions with relatively slow upper mantle velocities within the study area.

Session: Tectonics and Seismicity of Stable Continental Interiors

Type: Oral

Date: 4/19/2023

Presentation Time: 02:00 PM (local time)

Presenting Author: Chengping Chai

Student Presenter: No

Invited Presentation: Yes

Authors