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Magnetotelluric (MT) Upper Mantle Resistivity Structure of the Mississippi Embayment and Alabama-Oklahoma Lineament

Description: 

We investigate the upper mantle resistivity structure of the Mississippi Embayment (ME) and the Alabama-Oklahoma Lineament (AOL) using USMTArray and USGS long-period MT data. The ME is a deep sedimentary structure that includes the New Madrid seismic zone (NMSZ) and the AOL is a Precambrian to Paleozoic relic of plate tectonic events. Our investigation uses 2D profiles and the Occam2D inversion method. Due to the low resistivity sedimentary cover and mantle resistivity values, the long period MT data only provides good depth resolution up to about 100 km. The station spacing of 70 km also limits the horizontal spatial resolution of resistivity features. The upper ME upper mantle structure shows resistivity values around 1000 Ohm-m and with few distinct features. There is a NW-SE trending feature with lower resistivity (100 Ohm-m or less) west of ME in Arkansas corresponding to a low velocity zone at 80-120 km. A second more E-W low resistivity feature between 35N and 36N appears associated with a low velocity structure at 100-150 km. The AOL appears as a NW-SE trending feature with low resistivity (100 Ohm-m or less) that cuts off the ME trends to the north from the Gulf Coast (GC) features. The region corresponding to Bahamas Fracture seismic zone shows a higher resistivity of greater than 1000 Ohm-m from the depth of 50 km to 120 km in SW-NE profiles. The gulf coast low resistivity features appear associated with higher heat flow, possibly due to gulf coast crustal thinning, suggesting the dominance of temperature on mantle resistivity to the south. High heat flow with low resitivity may indicate a potential zone of weakness. Heat flow near and north of AOL is relatively low. Gravity data suggests lower densities are associated with the ME low resistivity features north of and including the AOL hence the possible influence of mantle fluids. Further measurements and research are needed to better define these mantle resistivity features.

Session: Earthquakes, Lithospheric Structure, and Dynamics in Stable Continental Region [Poster]

Type: Poster

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Kaushik

Student Presenter: Yes

Invited Presentation: 

Poster Number: 70

Authors