Abstract:

We carried out a highresolution Pwave velocity tomography of the Tibetan Plateau, Ashikule volcano clusters and surrounding areas by using arrivaltime data obtained from the nationwide seismic network, International Seismological Centre (ISC) as well as temporary seismic arrays deployed on the Tibetan Plateau. Our highresolution tomography shows that the Indian plate is revealed as a highvelocity anomaly and it is subducted beneath the Tibetan Plateau. The northern limit of the highvelocity anomaly has reached to the northern boundary of western Tibet, to the BangongNujiang suture under central Tibet and around the Jinsha River suture under eastern Tibet, suggesting the different northsouth distance that the Indian plate subducted northward. Our tomographic results suggest that the Indian plate has subducted to western Kunlun, around the Ashi volcano. To the north, the Tarim block shows a prominent high velocity anomaly. We found obvious low velocity anomalies and magma upwelling path beneath the Ashi volcano. In the mantle transition zone, there is a low velocity zone beneath the Ashi volcano. The Ashikule volcano clusters could be formed by the decompression melting of asthenospheric materials and magma upwelling.

Key words: Tibetan Plateau, Ashi volcano, Tarim block, seismic tomography