Australia: The Land Where Time Began

A biography of the Australian continent 

Gorkha Earthquake, Nepal – Slip Pulse and Resonance of the Kathmandu Basin during the 2015 event

Understanding of the physics of earthquakes and associated ground shaking is enhanced by detailed geodetic imaging of ruptures during earthquakes. This M_w 7.8 earthquake that occurred on 25 April 2015 is the first large continental megathrust rupture that has occurred beneath a high-rate (5 Hertz) Global Positioning System (GPS) network. Galetzka et al. used the GPS and interferometric synthetic aperture radar to model the earthquake rupture as a slip pulse of about 20 km wide, of a duration of about 6 seconds, which attained a peak sliding velocity of 1.1 m/s, which propagated at about 3.3 km/s over 140 km toward the Kathmandu Basin. A large slip-weakening distance, about 5 m, was indicated by the smooth onset of slip, which caused moderate shaking at frequencies greater than 1 hertz; peak ground acceleration, about 16 % of the gravity of the Earth, and minimised damaged to vernacular residences (traditional houses). The collapse of tall structures, including cultural artefacts, was caused by whole-basin resonance at a period of 4-5 seconds.

Sources & Further reading

1. Galetzka, J., D. Melgar, J. F. Genrich, J. Geng, S. Owen, E. O. Lindsey, X. Xu, Y. Bock, J.-P. Avouac, L. B. Adhikari, B. N. Upreti, B. Pratt-Sitaula, T. N. Bhattarai, B. P. Sitaula, A. Moore, K. W. Hudnut, W. Szeliga, J. Normandeau, M. Fend, M. Flouzat, L. Bollinger, P. Shrestha, B. Koirala, U. Gautam, M. Bhatterai, R. Gupta, T. Kandel, C. Timsina, S. N. Sapkota, S. Rajaure and N. Maharjan (2015). "Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake, Nepal." Science 349(6252): 1091-1095.