资源环境科技发展态势分析平台

The crustal structure of Western Nepal is studied for the first time by performing receiver function analysis on teleseismic waveforms recorded at 16 seismic stations. The Moho geometry is imaged as it deepens from similar to 40-km depth beneath the foothills and the Lesser Himalaya to similar to 58-km depth beneath the Higher Himalayan range. A midcrustal low-velocity zone is detected at similar to 15-km depth along similar to 55-km horizontal distance and is interpreted as the signature of fluids expelled from rocks descending in the footwall of the Main Himalayan Thrust. Our new image allows structural comparison of the Moho and of the Main Himalayan Thrust geometry along-strike of the Himalayas and documents long-wavelength lateral variations. The general crustal architecture observed on our images resembles that of Central Nepal; therefore, Western Nepal is also expected to be able to host large (M-W>8) megathrust earthquakes, as the 1505 CE event.

Plain Language Summary We investigate the Earth's crust in Western Nepal. We use 16 stations to detect waves from far-away earthquakes, and using these we make an image of the structure of the crust. We find that the crust is getting thicker beneath the Himalaya and that fluids are locally present in the upper part of the crust. As this image is similar to the one we know in Central Nepal, where major earthquakes happened, it is possible that major earthquakes will also happen in Western Nepal in the future (without knowing when).