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

Abstract

Abstract The 2013 Sea of Okhotsk deep earthquake ( M w 8.3), which was recorded by many global seismic stations with adequate coverage of azimuth and distance, provided an opportunity to understand the global characteristics of ground shaking. Peak ground accelerations (PGAs) from the Sea of Okhotsk earthquake decreased with distance up to 120° and peaked at a distance of 140°–150°. The variation as a function of distance is similar to that of the 1994 Bolivia earthquake. PGA values at distances between 40° and 85° are associated with vertical components of direct P waves, and the values are in a range from 10 −4 to 10 −2 m/s. The average decay with distance agrees with that of the P ‐wave amplitude predicted by the ray theory using lower‐mantle attenuation in a range of previously obtained models. Frequencies characterizing the PGA decay are between 0.8 and 1.8 Hz. In agreement with observations from other deep earthquakes, the P ‐wave radiation pattern can affect the decay curves of PGA with distance by changing the amplitude of P waves in the frequency range. Spatial variations in PGA can depend on the tectonic setting; large values of PGA are observed in stable continents and old seas, whereas small values are observed in tectonically active regions. Considering observations from the Sea of Okhotsk deep earthquakes, it is likely that PGA values have a positive correlation with shear‐velocity variations at depths of around 100–150 km below the stations.