Frequency Dependent Damage Pattern in Kathmandu Valley Due to Mw 7.8 Gorkha Earthquake

Abstract

The Mw 7.8 Gorkha Earthquake (25th April 2015) is powerful earthquake ripped through Central Nepal occurs about 77 Km northwest of Kathmandu Valley. Several studies reveal the fact that comparatively larger earthquake damage in the Kathmandu valley are associated with the valley ground structure. Study focus on reason behind clustering of damages due to mainshock (7.8 Mw) inside Kathmandu valley in certain pattern and its dependency with frequency content of the shattered waves. Data used to meet objective of present research are ground motion data and damage data, for ground motion data seismic stations inside the valley are use. The damage data are collected by both primary and secondary sources. Frequency domain spectral analysis is incorporated in research and found that the maximum power and amplitude, associated, and attributed for particular narrow frequency band. Spatial component of frequency is wavelength which may indicate periodic repetition of maximum power with crest and trough. To estimate spatial distribution of maximum amplitude simplified wave relation is used. Study reveals that the lateral extension of the peak destruction zone as fourth of wavelength and the successive distance between peak destruction zones is half of wavelength. Peak destruction zone, the zone where the damage is maximum and lies either on crest or trough of the propagated wave. Study reveals that propagation of waves is S45oE form the epicenter of Gorkha Earthquake. Heterogeneity in damage on peak destruction zone can be contributed by the variation in geology of Kathmandu Valley.