Relationship between Crustal Structure and Intraplate Seismicity beneath the Southeastern United States

Session: Seismicity and Tectonics of Stable Continental Interiors
Type: Oral
Date: 4/30/2020
Time: 11:00 AM
Room: 240
Description: 

The Southeastern United States (SEUS) lies on a passive margin far away from ongoing tectonic deformation, yet remains capable of hosting damaging earthquakes. Crustal and lithospheric structure within the SEUS preserves a complex history of continental collisions, rifting and volcanism that has shaped it over billions of years leaving behind a chaotic assortment of accreted terranes and faults. Zones of weakness in the lithosphere at structural boundaries inherited from past collisional events are a proposed explanation for the intraplate seismicity; however, the extent and magnitude of intra-lithospheric variations associated with intraplate seismicity has not been fully explored. Therefore, mapping variations in lithospheric structure can both clarify the tectonic history of the region and highlight possible mechanisms that control intraplate seismicity.

Typically, P-to-s converted waves, analyzed through the receiver function technique are used to constrain interfaces in the lithosphere, but their application to the SEUS has proven difficult as large amplitude reverberations from basins and Atlantic coastal plain sediments can overprint signal from deeper crustal and lithospheric structure. Therefore, we use reverberation-corrected P-to-s receiver functions (PRFs) and common conversion point (CCP) stacking to constrain crustal and lithospheric variations across the entire SEUS. We find evidence for deep mid-crustal layering (or a “double-Moho”) deepening westward beneath the Blue Ridge in eastern Tennessee as well as a shallow mid-crustal layer deepening eastward which has been interpreted to mark the location of the suture between Laurentia and Gondwana during the formation of Pangea (e.g. Hopper et al. 2017). While we find no evidence that a more prominent lithosphere-asthenosphere boundary or mid-lithospheric discontinuities are associated with the location of intraplate earthquakes, we do find evidence that laterally abrupt variations in crustal thickness are associated with regions hosting intraplate seismicity.

Presenting Author: Erin Cunningham

Authors