Seismic Attenuation Characteristics along the Hi-CLIMB Profile in Tibet from Lg Q Inversion

We investigate the Q of crustal Lg waves along the Himalayan-Tibetan Continental Lithosphere during Mountain Building (Hi-CLIMB) profile in Tibet using a reliable two-station method. Four earthquakes of M >= 5.5 recorded along a 800-km-long densely-spaced seismic profile are used to extract Lg-wave spectra. One hundred seven high quality interstation paths that allow us to use the standard two-station method for Lg Q measurement are selected from 2369 possible pairs. By using those 107 interstation Q(0) (1 Hz Lg Q) values as input, lateral variations in attenuation characteristics are derived through inversion. The region has Q(0) estimates ranging from 88 +/- 5 to 165 +/- 15, with the lowest value in the Qiangtang terrane and the highest across some part of the lower Himalaya. The lowest value is attributed to the high Poisson's ratio, higher temperatures, as well as partial melts in the crust. The results do not contain any detectable variation in Q(0) either across the Himalaya-Tibet collision zone (i.e., the Indus-Tsangpo suture zone) or along the major Bangong-Nujiang suture zone (BNSZ). Consistent low Q(0) values along the Hi-CLIMB profile manifest the presence of omnipresent partial melting of the crust throughout the plateau.