Nowcasting earthquakes in Iran: A quantitative analysis of earthquake hazards through natural times

Abstract

Despite the extremely complex earthquake generation mechanism in a driven nonlinear threshold system, simple empirical scaling laws apply to the collective behavior of earthquakes in a network of geological faults. The physical interpretation of these properties and associated relations exhibit a wealth of information to study earthquake processes and consequent earthquake hazards in a defined area. In this article, an area-source-based earthquake nowcasting method is implemented to statistically determine the current state of earthquake hazards at several cities of Iran through the formulation of a discrete time-series of cumulative interevent counts, known as natural times. Use of natural times to mark the evolution of the seismic process, rather than the passage of clock time, essentially provides spatiotemporal and clustering invariable properties. Statistical inference of natural time counts corresponding to M ≥ 6.0 events results in an earthquake potential score (%) as Ahvaz (94), Hamadan (50), Isfahan (98), Karaj (76), Kerman (78), Kermanshah (73), Mashhad (40), Qom (92), Rasht (21), Shiraz (98), Tabriz (45), Tehran (78), Urmia (51), and Zahedan (53). These nowcast values provide a snapshot of the current progression of a city in its earthquake cycle of large-sized events and thus facilitate better decision-making, city-planning, and earthquake awareness, leading to an efficient seismic risk reduction strategy in the densely populated study region.