Imaging the Lithosphere under Southern Illinois Basin based on Ozark-Illinois-INdiana-Kentucky (OIINK) Flexible Array Experiment
Abstract
The OIINK Flexible Array experiment was designed to improve our understanding of the deep structure and tectonic processes of the continental interior of North America. This experiment will ultimately utilize 140 FA stations spanning across the southern Illinois Basin and its adjacent structural units being merged with USArray Transportable Array and broadband data from the New Madrid seismic network. We analyzed local seismicity within the transitional region between Ozark Dome and Illinois Basin. The higher density of stations yields approximately twice the number of events located by the New Madrid seismic network for this region. Earthquakes inside this transitional region are distributed diffusely around the St. Genevieve Fault Zone with predominantly strike-slip focal mechanisms. Teleseismic P-wave travel-time residuals showed a variation of about +1.0 s from west to east across the array. This is approximately consistent with the sediment thickness pattern from existing models for Illinois Basin. However, the delay times derived from those models are not sufficient to account for the full difference. This might be indication of the deep velocity contrast across the boundary between Ozark dome and Illinois Basin. The relative P-wave travel-time data were used in teleseismic travel-time tomography processing. The preliminary result shows a velocity structure of the deep crust and upper mantle that correlates with major structural units. Finally, the receiver function stacks determined from OIINK broadband data indicates that the crust is greater than 40 km thick in much of this region. The crust thickens significantly at the transition between the Illinois Basin and Ozark dome to approach 50 km in eastern Missouri. Furthermore, the pulses used to mark the Moho interface have different widths and amplitudes in Illinois Basin from those in the surrounding areas. Corrections for basin sediments are needed to better define the Moho geometry. Additional work using other wavefield processing methods and the most recent data is in progress.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.T23B2583Y
- Keywords:
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- 7218 SEISMOLOGY Lithosphere;
- 8103 TECTONOPHYSICS Continental cratons;
- 7230 SEISMOLOGY Seismicity and tectonics;
- 7270 SEISMOLOGY Tomography