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Horizontally-polarized (SH) shear displacement wavefield recorded at a subset of GSN stations (54 - 72 degrees epicentral distance), plotted along zimuths from the epicenter. Note the approximately 2 times larger amplitudes towards the NNW (e.g., ARU) relative to the SSE (CASY). This radiative directionality is indicative of a NNW rupture propagation direction. Each 10-degree azimuthal increment corresponds to a displacement of 5 mm.
Credit: Richard Aster, New Mexico Institute of Mining and Technology