Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake, Nepal

The bigger they are, the harder they fall The magnitude 7.8 Gorkha earthquake hit Nepal on 25 April 2015. The earthquake killed thousands and caused great damage. Galetzka et al. determined how the fault that caused this earthquake ruptured. The rupture showed a smooth slip pulse 20 km wide that moved eastward along the fault over about 6 s. The nature of the rupture limited damage to regular dwellings but generated shaking that collapsed taller structures. Science, this issue p. 1091 Continuous GPS and InSAR measurements record slip on the fault responsible for the 2015 Mw 7.8 Gorkha earthquake in Nepal. Detailed geodetic imaging of earthquake ruptures enhances our understanding of earthquake physics and associated ground shaking. The 25 April 2015 moment magnitude 7.8 earthquake in Gorkha, Nepal was the first large continental megathrust rupture to have occurred beneath a high-rate (5-hertz) Global Positioning System (GPS) network. We used GPS and interferometric synthetic aperture radar data to model the earthquake rupture as a slip pulse ~20 kilometers in width, ~6 seconds in duration, and with a peak sliding velocity of 1.1 meters per second, which propagated toward the Kathmandu basin at ~3.3 kilometers per second over ~140 kilometers. The smooth slip onset, indicating a large (~5-meter) slip-weakening distance, caused moderate ground shaking at high frequencies (>1 hertz; peak ground acceleration, ~16% of Earth’s gravity) and minimized damage to vernacular dwellings. Whole-basin resonance at a period of 4 to 5 seconds caused the collapse of tall structures, including cultural artifacts.