Active structures of the Himalayan-Tibetan orogen and their relationships to earthquake distribution, contemporary strain field, and Cenozoic volcanism

Abstract

We have compiled the distribution of active faults and folds in the Himalayan-Tibetan orogen and its immediate surrounding regions into a web-based digital map. The main product of this study is a compilation of active structures that came from those documented in the literature and from our own interpretations based on satellite images and digital topographic data. Our digital tectonic map allows a comparison between the distribution and kinematics of active faults with the distribution and focal mechanisms of earthquakes. The active tectonic map is also compared with the contemporary velocity field, obtained by global positioning system studies, that allows a better assessment of partitioning of decadal strain-rate fields across individual active structures that may have taken tens of thousands of years to a million years to develop. The active tectonic map provides a basis to evaluate whether the syncollisional late Cenozoic volcanism in Tibet was spatially related to the distribution and development of the active faults in the same area. These comparisons lead to the following findings: (1) Tibetan earthquakes >M5 correlate well with mappable surface faults; (2) the short-term strain-rate field correlates well with the known kinematics of the active faults and their geologic slip rates; and (3) Tibetan Neogene–Quaternary volcanism is controlled by major strike-slip faults along the plateau margins but has no clear relationship with active faults in the plateau interior. Although not explored in this study, our digital tectonic map and the distribution of Cenozoic volcanism in Tibet can also be used to correlate surface geology with geophysical properties such as seismic velocity variations and shear wave-splitting data across the Himalaya and Tibet.