Lg attenuation tomographic models of Himalaya and southern Tibet

- A tomographic image of Lg Q is developed for Himalaya and southern Tibet.
- Distinct variations in the crustal attenuation are observed from north to south across the whole region.
- The spatial variations in Q are consistent with the tectonic features and the physical state of the crust.
- The results are found to be comparable with the other parts of Himalaya and Tibet.

We investigate the Lg attenuation structure of the crust beneath the tectonically complex Himalaya and southern Tibet regions adopting a tomographic regionalization method. A total of 1671 earthquake waveforms registered at 38 seismic stations operated in the region are selected for the initial LgQ measurements using the standard two-station method. Q0 (1 Hz LgQ) values of 76 high quality interstation paths are finally considered as input for the tomographic inversion. The estimates of Q0 exhibit distinct variations in the crustal attenuation from north to south across the whole region. The zones of lowest Q0 values (< 50) are observed along the Main Central Thrust (MCT) in Sikkim, Lesser Himalaya and some parts of the Greater Himalaya. Southern Tibet is characterized by low Q0 (<  100) values. These observations are consistent with the results of body wave attenuation and velocity structure reported for the region. We interpret the variations in the attenuation characteristics in terms of both the intrinsic and scattering contributions caused by thermal effects, presence of aqueous fluids as well as heterogeneities present below these seismically active regions. Our results are found to be comparable with the other parts of Himalaya and Tibet.