Fatality rates of the M w ~8.2, 1934, Bihar–Nepal earthquake and comparison with the April 2015 Gorkha earthquake

Abstract

Large Himalayan earthquakes expose rapidly growing populations of millions of people to high levels of seismic hazards, in particular in northeast India and Nepal. Calibrating vulnerability models specific to this region of the world is therefore crucial to the development of reliable mitigation measures. Here, we reevaluate the >15,700 casualties (8500 in Nepal and 7200 in India) from the M w ~8.2, 1934, Bihar-Nepal earthquake and calculate the fatality rates for this earthquake using an estimation of the population derived from two census held in 1921 and 1942. Values reach 0.7-1 % in the epicentral region, located in eastern Nepal, and 2-5 % in the urban areas of the Kathmandu valley. Assuming a constant vulnerability, we obtain, if the same earthquake would have repeated in 2011, fatalities of 33,000 in Nepal and 50,000 in India. Fast-growing population in India indeed must unavoidably lead to increased levels of casualty compared with Nepal, where the population growth is smaller. Aside from that probably robust fact, extrapolations have to be taken with great caution. Among other effects, building and life vulnerability could depend on population concentration and evolution of construction methods. Indeed, fatalities of the April 25, 2015, M w 7.8 Gorkha earthquake indicated on average a reduction in building vulnerability in urban areas, while rural areas remained highly vulnerable. While effective scaling laws, function of the building stock, seem to describe these differences adequately, vulnerability in the case of an M w >8.2 earthquake remains largely unknown. Further research should be carried out urgently so that better prevention strategies can be implemented and building codes reevaluated on, adequately combining detailed ancient and modern data.

Post Earthquake Aggradation Processes to Hide Surface Ruptures in Thrust Systems: The M8.3, 1934, Bihar‐Nepal Earthquake Ruptures at Charnath Khola (Eastern Nepal)

“…This earthquake devastated a large area of central and eastern Nepal. The mesoseismal area with intensities ≥VIII, covered more than 10,000 km 2 (Ambraseys & Douglas, 2004;Sapkota et al, 2013Sapkota et al, , 2016. The (Adhikari et al, 2015).…”

Constraining Frictional Properties on Fault by Dynamic Rupture Simulations and Near‐Field Observations

“…On 25 April 2015, an M w 7.8 earthquake has struck central Nepal, 80 km northwest of Kathmandu, and produced strong shaking that caused extensive damage and killed more than 8500 people (Sapkota et al, ). The rupture starts at a hypocentral depth of ~15 km and propagates eastwards along the lower edge of the locked portion of the Main Himalayan Thrust (Avouac et al, ), where the Indian and the Eurasian plates collide at a rate of ~18 mm/yr (Lavé & Avouac, ).…”

Widespread ground motion distribution caused by rupture directivity during the 2015 Gorkha, Nepal earthquake

“…7, we found districts between 86 and 87°E to have fatality rates of 0.01 to 0.1%, which correspond to an intensity of 7 (ref. 20). In these far eastern districts, included is the district of Mount Everest, where avalanches induced by seismic ground motions killed 20 people and injured 120 people21.…”