Mid-Continent Section

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The earthquake process in Oklahoma


The use of modern broadband moment tensor inversion has lead to a catalog of over 180 earthquakes, with moment magnitudes > 3.0, of which 140 have been determined since the beginning of 2014. With the exception of a few normal faulting events near Kansas, the vast majority involve strike-slip faulting with compressive stress axes oriented NE-SW to E-W. The alignment of one of the nodal planes with the linear patterns of epicenters determined using multiple event relocations (McNamara et al, 2015) permits the specification of the fault plane for many areas. The other significant feature is that the majority of events are shallow as evidenced by the moment tensor depths and the excitation of short period fundamental mode surface waves. Since the depths depend on the local velocity model used, a region specific crustal model was developed that accounts for surface-wave Love/Rayleigh phase/group velocity dispersion in the 2–100 period range, teleseismic P-wave receiver functions and short-period transverse component recordings at distance to 50 km. Finally the high frequency recordings from about 1000 components and 1400 earthquakes are examined to constrain ground motion prediction models in the 0.25 – 20 Hz band used in seismic hazard analysis.