Aftershock activity of the 2015 Gorkha, Nepal, earthquake determined using the Kathmandu strong motion seismographic array

Masayoshi Ichiyanagi,Subeg Bijukchhen,Michiko Shigefuji,Tsutomu Sasatani,Megh Raj Dhital,Nobuo Takai,Sudhir Rajaure,Hiroaki Takahashi

doi:10.1186/s40623-016-0402-8

Masayoshi Ichiyanagi, Subeg Bijukchhen + Show 6 more

Open Access

https://doi.org/10.1186/s40623-016-0402-8

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Abstract

The characteristics of aftershock activity of the 2015 Gorkha, Nepal, earthquake (Mw 7.8) were evaluated. The mainshock and aftershocks were recorded continuously by the international Kathmandu strong motion seismographic array operated by Hokkaido University and Tribhuvan University. Full waveform data without saturation for all events enabled us to clarify aftershock locations and decay characteristics. The aftershock distribution was determined using the estimated local velocity structure. The hypocenter distribution in the Kathmandu metropolitan region was well determined and indicated earthquakes located shallower than 12 km depth, suggesting that aftershocks occurred at depths shallower than the Himalayan main thrust fault. Although numerical investigation suggested less resolution for the depth component, the regional aftershock epicentral distribution of the entire focal region clearly indicated earthquakes concentrated in the eastern margin of the major slip region of the mainshock. The calculated modified Omori law’s p value of 1.35 suggests rapid aftershock decay and a possible high temperature structure in the aftershock region.

Highlights

On April 25, 2015, a large shallow earthquake (Mw 7.8) occurred in the Gorkha region of central Nepal
We present the characteristics of the aftershock activity using original data from the local seismographic array
Hypocenter estimation and location error evaluation clarified the characteristics of aftershock activity

Summary

Introduction

On April 25, 2015, a large shallow earthquake (Mw 7.8) occurred in the Gorkha region of central Nepal. This array was designed to collect continuous waveform data in order to evaluate strong motion forecasting of the anticipated destructive earthquakes. We present the characteristics of the aftershock activity using original data from the local seismographic array. Data and analysis The Kathmandu strong motion seismographic array was initiated with four stations along an east–west alignment in the city (Fig. 1a).

Results

Conclusion