Quantifying the current state of earthquake hazards in Nepal

Abstract

Quantitative estimates of present-day earthquake hazard in major cities are essential for effective policymaking, community development, and seismic risk reduction. In this study, we develop a statistical analysis of natural times in Nepal to compute earthquake potential score (EPS) that describes the current level of seismic progression of a city through irregular repetitive cycle of regional earthquakes. The method, known as earthquake nowcasting (Rundle et al., 2016), uses a discrete time domain of natural times, cumulative counts of small interevent earthquakes, to characterize the present state of fault system by way of considering all earthquake events, including dependent, induced, or triggered seismicity. Data analysis and statistical inference of natural times corresponding to M ​≥ ​6 events assign EPS values between 59% and 99% to 24 major cities of Nepal, with the scores of metropolitan areas Kathmandu (95%), Pokhara (93%), Lalitpur (95%), Bharatpur (93%), Biratnagar (92%), and Birganj (93%). Physically, these nowcast scores, viewed as a way of tectonic stress accumulation since the last event, provide a realistic estimate on how far along is a city in its earthquake cycle of large sized events at current time. The proposed analysis and emanated results produce valuable information to the academia, industry, and public on the current dynamical state of seismic hazard in the highly earthquake prone Nepal region.