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Toward a unified near-field intensity map of the 2015 Mw 7.8 Gorkha, Nepal, Earthquake

December 1, 2017

We develop a unified near-field shaking intensity map for the 25 April 2015 Mw 7.8 Gorkha, Nepal, earthquake by synthesizing intensities derived from macroseismic effects that were determined by independent groups using a variety of approaches. Independent assessments by different groups are generally consistent, with minor differences that are likely due in large part to differences in spatial sampling. Throughout most of the near-field region, European Macroseismic Scale (EMS-98) intensities were generally close to 7 EMS. In the Kathmandu Valley, intensities were somewhat higher (6.5–7.5) along the periphery of the valley and in the adjacent foothills than in the central valley, where they were ≈6. The results are consistent with instrumental intensity values estimated from available data using a published relationship between peak ground acceleration (PGA) and intensity. Using this relationship to convert intensities to PGA, we estimate strong-motion PGA de-amplification factors of ≈0.7 in the central Kathmandu Valley, with amplification of ≈1.6 in adjacent foothills. The results support the conclusion that the Kathmandu Valley experienced a pervasively nonlinear response during the Gorkha main shock.

Publication Year 2017
Title Toward a unified near-field intensity map of the 2015 Mw 7.8 Gorkha, Nepal, Earthquake
DOI 10.1193/120716EQS226M
Authors Sujan Raj Adhikari, Gopi Baysal, Amod Dixit, Stacey Martin, Mattieu Landes, Remy Bossu, Susan E. Hough
Publication Type Article
Publication Subtype Journal Article
Series Title Earthquake Spectra
Index ID 70198117
Record Source USGS Publications Warehouse
USGS Organization Earthquake Science Center