Teleseismic Peak Ground Accelerations from the 24 May 2013 Sea of Okhotsk Deep Earthquake

Abstract:

The 2013 Sea of Okhotsk deep earthquake (Mw8.3) generated felt reports worldwide including ones from Moscow (~58 degrees) and Dubai (~76 degrees) (NEIC, 2013). The earthquake was recorded by many global seismic stations with a good coverage of azimuth and distance, which provides an opportunity to understand the global characteristics of ground shaking. Peak ground accelerations (PGA) from the Sea of Okhotsk deep earthquake decrease with distance up to 120 degrees, and have a peak at a distance of 140-150 degrees. The variation as a function of distance is similar to the one shown by Anderson et al. (1995) for the 1994 Bolivia earthquake. PGA at distances between 40 and 85 degrees are associated with vertical components of direct P waves, and the values are mostly in a range from 0.1 to 1 gal. The decay with distance is in agreement with that of P wave amplitude predicted by the ray theory with t* in the range between the lower-mantle attenuation models of Hwang and Ritsema (2011) and PREM. Frequencies characterizing the PGA decay are in a range between 0.8 and 1.8 Hz. As also suggested by observations from other large deep earthquakes, the radiation pattern of P waves can change the decay curves of PGA with distance, by affecting the amplitude of P waves in the frequency range. Spatial variations of PGA are likely to be characterized by the tectonic setting; large values of PGA appear in stable continents and old seas, whereas small values are observed in tectonically active regions. Positive correlation is observed between PGA values and velocity perturbations of the 3-D global shear velocity model at depths shallower than 100 km.