Kathmandu Basin as a local modulator of seismic waves: 2-D modelling of non-linear site response under obliquely incident waves

SUMMARY The 2015 Mw 7.8 Gorkha, Nepal earthquake is the largest event to have struck capital city of Kathmandu in recent times. One its surprising features was frequency content recorded ground motion, exhibiting a notable amplification at low frequencies (<2 Hz) and contrasting depletion higher frequencies. latter has been partially attributed damper behaviour basin. While such weak high-frequency motion helped avoiding severe damage city, catastrophic outcomes earlier earthquakes region attest role basin as broad-band amplifier, addition possible source effects. Given possibility future strong events region, our main objective elucidate seismic by focusing on site We numerically model 2-D P–SV wave propagation broad band (up 10 Hz), incorporating most data for geometry, soil stratigraphy geotechnical properties, accounting non-linear effect multidimensional plasticity propagation. find that: (1) generally amplifies Hz); (2) waves with large incidence angles relative vertical can dramatically amplify high respect bedrock despite damping non-linearity (3) spatial distribution peak amplitudes along highly sensitive (angle direction), favouring larger values near edges located closer source, observed during event. Our modelling approach findings support ongoing resilience practices guide hazard assessment studies other sites that feature similar complexities dynamic behaviour.