Joint Local and Teleseismic Tomography in the Central United States and Implications for the Origin of Intraplate Seismicity

Session: Seismicity and Tectonics of Stable Continental Interiors
Type: Oral
Date: 4/30/2020
Time: 02:00 PM
Room: 240
Description: 

We present 3D crustal and upper mantle P-wave (Vp) and S-wave (Vs) velocity models for the northern Mississippi Embayment (NME) and the Illinois Basin using the USArray transportable network and stations deployed in the Northern Embayment Lithosphere Experiment (NELE) and the Ozark-Illinois-Indiana-Kentucky (OIINK) FlexArrays. Our velocity models contain a narrow low velocity zone (LVZ) below the NME, in agreement with several past studies.  Our results bring new insight into the crust and upper mantle velocity structure associated with the Illinois Basin.  A high-velocity anomaly is present in the crust beneath the central area of the Illinois Basin that coincides with the La Salle deformation belt, thought to represent compressional deformation associated with the distant Appalachian-Ouachita orogeny.  We find a narrow LVZ that extends from the NME to the northwest along the southwest boundary of the Illinois Basin.  This LVZ dips to the northwest and reaches a depth of 250 km. A broader LVZ is present below 300 km, along the dip direction. The presence of the LVZ below the southwest boundary of the Illinois Basin corresponds to the location of the Ste. Genevieve seismic zone.  A low velocity region extending from the base of the crust to a depth of about 100 km is present below the central portion of the Illinois Basin, in agreement with prior studies.  The location of this LVZ roughly corresponds to the Wabash Valley seismic zone.  We discuss possible origins of the imaged LVZs and their relationship to deeper mantle features as well as their possible influence on earthquake generation.  

Presenting Author: Yu Geng

Authors