Correlation of the slope of the initial part of P-wave envelope, hypocenter depth and plate boundary

Abstract We investigated correlation of the slope of the initial part of P-wave envelope, hypocenter depth and plate boundaries by B -Δ method, which is used to determine epicentral distances in the Japan Meteorological Agency and Japan Railway Company earthquake early warning (EEW) systems. The Tohoku region was chosen as the study region. 19,899 strong motion data for 265 events with magnitudes in the range from 5.0 to 7.6 from KiK-net (Kiban Kyoshin network) had been collected. The coefficient c to investigate is obtained from the linear relation between log B and logΔ. Compared to the hypocenter depth, the coefficients c of events is more likely to decide by the spatial correlation of the plate boundaries. The differences are likely to be due to earthquake characteristics, since deeper events in the subducting slabs the structural effects are likely to be larger than or comparable to those for shallow crust events.