EVIDENCE FROM EARTHQUAKE DATA FOR A PARTIALLY MOLTEN CRUSTAL LAYER INSOUTHERN TIBET

Earthquake data collected by the INDEPTH-II Passive-Source Experiment show that there is a substantial south to north variation in the veloc ity structure of the crustal beneath southern Tibet. North of the Zang bo suture, beneath the southern Lhasa block, a mid-crustal low-velocit y zone is revealed by inversion of receiver functions, Rayleigh-wave p hase velocities, and modeling of the radial component of teleseismic P -waveforms, Conversely, to the south beneath the Tethyan Himalaya, no low-velocity zone was; observed, The presence of the midcrustal low-ve locity zone in the north implies that a partially molten layer is in t he middle crust beneath the northern Yadong-Gulu rift and possibly muc h of southern Tibet.