Spatial distribution of seismic cycle progression in northeast India and Bangladesh regions inferred from natural time analysis

Abstract

The ability to determine the current state of seismic cycle of large sized earthquakes is of profound importance in societal policymaking and disaster preparation. In this article, we present a probabilistic formulation of event-based natural time counts to develop earthquake potential score (EPS) at 36 cities from northeast India, Bangladesh, and adjoining areas. The time-dependent natural time analysis provides an attractive regional seismic hazard evaluation method, because it (1) exhibits spatiotemporal and clustering invariability, ensuring model consistency, (2) considers "seismic cycles" for a network of faults in a defined area, and (3) enables some physical interpretations aligned with earthquake generation process characterized by stress accumulation and moment release. The modeling results for M ≥ 6 events reveal that EPS values lie between 41 and 94%, with the scores of Agartala (91%), Aizawl (84%), Dimapur (80%), Guwahati (41%), Imphal (90%), Malda (70%), Shillong (52%), Siliguri (73%), Barisal (59%), Chittagong (94%), Comilla (88%), Dhaka (78%), Mymensingh (81%), Narayanganj (77%), Rangpur (55%), and Sylhet (60%). These values essentially serve as a yardstick to statistically assess the current state of regional seismic cycle progression in the study region, bringing out some key information to the decision-makers, engineers, scientists, and citizens to improve earthquake preparedness and mitigation strategies.