The Influence of Surface Topography on the Weak Ground Shaking in Kathmandu Valley during the 2015 Gorkha Earthquake, Nepal
Sensors (Basel). 2020 Jan 26;20(3):678. doi: 10.3390/s20030678.
Mark van der Meijde 1 , Md Ashrafuzzaman 1 2 , Norman Kerle 1 , Saad Khan 1 3 , Harald van der Werff 1
1 Department of Earth Systems Analysis, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, 7500 AE Enschede, The Netherlands.
2 Roads and Highways Department, Government of the People's Republic of Bangladesh, Sarak Bhaban, Tejgaon, Dhaka 1208, Bangladesh.
3 Department of Geology, Bacha Khan University Charsadda, Charsadda 24420, Khyber Pakhtunkhwa, Pakistan.
DOI: 10.3390/s20030678
It remains elusive why there was only weak and limited ground shaking in Kathmandu valley during the 25 April 2015 Mw 7.8 Gorkha, Nepal, earthquake. Our spectral element numerical simulations show that, during this earthquake, surface topography restricted the propagation of seismic energy into the valley. The mountains diverted the incoming seismic wave mostly to the eastern and western margins of the valley. As a result, we find de-amplification of peak ground displacement in most of the valley interior. Modeling of alternative earthquake scenarios of the same magnitude occurring at different locations shows that these will affect the Kathmandu valley much more strongly, up to 2-3 times more, than the 2015 Gorkha earthquake did. This indicates that surface topography contributed to the reduced seismic shaking for this specific earthquake and lessened the earthquake impact within the valley.
Keywords: Nepal; amplification; digital elevation model; earthquake; modelling.