T‐waves excited by S‐waves and oscillated within the ocean above the Southeastern Taiwan Forearc

The generation processes of T‐waves were investigated from seismograms produced by a local intermediate‐depth earthquake and recorded at one short‐period station in Taiwan. The first group of T‐phases arrived 44 seconds after the S‐phases, while the following 2 groups consistently had the same travel‐time difference of about 88 seconds each. Analyses of the ray paths and travel‐times of these phases show that the T‐waves were converted from the S‐waves and oscillated within the ocean above the forearc in the southeastern Taiwan area. Further comparisons of these results with those of previous studies suggest that the generation of T‐waves is probably dependent on the incidence angles of the seismic waves. The T‐waves were converted from S‐waves when the incidence angles of the seismic waves were near vertical, whereas they were generated from P‐waves when those angles were near horizontal.