Two-dimensional numerical modeling suggests preferred geometry of intersecting seismogenic faults
Published:January 01, 2007
Abhijit Gangopadhyay, Pradeep Talwani, 2007. "Two-dimensional numerical modeling suggests preferred geometry of intersecting seismogenic faults", Continental Intraplate Earthquakes: Science, Hazard, and Policy Issues, Seth Stein, Stéphane Mazzotti
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We undertook a parametric study, using a two-dimensional distinct element method, to investigate if there is a preferred geometry of intersecting faults that may favor the occurrence of intraplate earthquakes. This model subjects two and three vertical, intersecting faults within a block to a horizontal force across them, representing the maximum horizontal compression (SHmax). The main fault is oriented at an angle α with respect to SHmax, and β is the interior angle between the main fault and the intersecting fault. The third fault is oriented parallel to the main fault and is half its length. The distribution of shear stresses is examined along the faults for different values of α and β, and varying lengths of the main and intersecting faults. In all cases, maximum shear stresses are generated at the fault intersections. The modeling results reveal that the magnitudes of the shear stresses depend on the values of α and β, with an optimum range for α between 30° and 60°. In the case where the sign of the shear stress on the intersecting fault is opposite that on the main fault, the largest stresses at the fault intersections are obtained when β is between 65° and 125°. When the stresses on these two faults are of the same sign, the largest stress values at the intersections are obtained when 145° ≤ β ≤ 170°. The results of the modeling are consistent with the observed geometry of faults in the New Madrid and Middleton Place Summerville seismic zones.