The travel time delay correction of seismic wave at CEORKA strong ground motion observation stations in the Osaka Basin

Arrival times of seismic waves at sites located over sedimentary basins show travel time delays due to the difference in seismic wave velocity between basement rocks and overlying sediments. This time delay leads to an error of the hypocenter determination. We determined the corrected values for the travel time delay at the 13 CEORKA sites distributed in the Osaka Basin. Using the heuristic search and empirical criteria, we could achieve an effective estimation for the travel time delay correction caused by the sedimentary cover. For earthquakes in and around the Osaka Basin, this correction method may improve the accuracy of the hypocenter determination using only seismograms acquired on sites over sediments.