ISC locations for earthquakes beneath Tibet indicate a random distribution of events down to a depth of about 50 km. This distribution would be expected from a relatively cool crust which would allow the seismo-genic zone to extend to such depths. A detailed investigation of the Tibetan earthquakes, with magnitude greater than 5.5 from 1964 to 1986, yields a distinctly different picture. Waveform modeling of depth phases indicates that only a few events from this population is actually deeper than 25 km. These few events occurred near the edges of the Plateau where active subduction is occurring as suggested by the thrust-like nature of their mechanisms. The events, averaging the entire population, occurred earlier than indicated by the ISC by about 3 seconds which leads to about a 1.5% and 0.5% over estimation of Pn and Sn velocities respectively applying ISC tables and standard flat-layered models. A more serious error occurs if the Pn and Sn velocities are determined by correcting for source depth but assuming the ISC origin times.