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Stressing of the New Madrid seismic zone by a lower crust detachment fault

Journal of Geophysical Research B: Solid Earth

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Abstract

A new mechanical model for the cause of the New Madrid seismic zone in the central United States is analyzed. The model contains a subhorizontal detachment fault which is assumed to be near the domed top surface of locally thickened anomalous lower crust ("rift pillow"). Regional horizontal compression induces slip on the fault, and the slip creates a stress concentration in the upper crust above the rift pillow dome. In the coseismic stage of the model earthquake cycle, where the three largest magnitude 7-8 earthquakes in 1811-1812 are represented by a single model mainshock on a vertical northeast trending fault, the model mainshock has a moment equivalent to a magnitude 8 event. During the interseismic stage, corresponding to the present time, slip on the detachment fault exerts a right-lateral shear stress on the locked vertical fault whose failure produces the model mainshock. The sense of shear is generally consistent with the overall sense of slip of 1811-1812 and later earthquakes. Predicted rates of horizontal strain at the ground surface are about 10-7 year-1 and are comparable to some observed rates. The model implies that rift pillow geometry is a significant influence on the maximum possible earthquake magnitude.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Stressing of the New Madrid seismic zone by a lower crust detachment fault
Series title:
Journal of Geophysical Research B: Solid Earth
Volume
102
Issue:
12
Year Published:
1997
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research B: Solid Earth
First page:
27623
Last page:
27633
Number of Pages:
11