SURFACE WAVE TOMOGRAPHY FROM AMBIENT NOISE IN CENTRAL U.S. AND ITS IMPLICATIONS FOR ILLINOIS BASIN AND NEW MADRID SEISMIC ZONE

To a better understanding of evolution process of midcontinent, surface wave interferometry combined with tele seismic Rayleigh wave tomographic inversion were employed in central continent area to retrieve the velocity structure of the crust and uppermost mantle.

Seismic ambient noise cross-correlation between station pairs over long period of time could effectively retrieve the empirical green’s function (EGF) estimates especially at short period. Based on ambient noise interferometry, the surface wave dispersion curves were inverted and further used to provide a better estimate of the velocity structure of the crust and uppermost mantle.

We applied such interstation interferometry method at short period (T = 10 – 40 s) over midcontinent region among 276 stations from EarthScope Transportable Array (TA) and OIINK (Ozarks–Illinois–Indiana–Kentucky) Flexible Array (XO) to investigate lithospheric structure beneath the central U.S. Combined with long period inversion (T = 40 – 100 s), a new tomography of shear velocity structure was presented for the New Madrid intraplate seismic zone and the Illinois Basin in the midcontinent of America. The proposed velocity structure could shed some lights on process of the terrane accretion, cratonization, continent rifting as well as the intraplate seismicity in central U.S.