Nowcasting earthquakes

Abstract

Nowcasting is a term originating from economics and finance. It refers to the process of determining the uncertain state of the economy or markets at the current time by indirect means. We apply this idea to seismically active regions, where the goal is to determine the current state of the fault system and its current level of progress through the earthquake cycle. In our implementation of this idea, we use the global catalog of earthquakes, using "small" earthquakes to determine the level of hazard from "large" earthquakes in the region. Our method does not involve any model other than the idea of an earthquake cycle. Rather, we define a specific region and a specific large earthquake magnitude of interest, ensuring that we have enough data to span at least~20 or more large earthquake cycles in the region. We then compute the earthquake potential score (EPS) which is defined as the cumulative probability distribution P(n < n(t)) for the current count n(t) for the small earthquakes in the region. From the count of small earthquakes since the last large earthquake, we determine the value of EPS = P(n < n(t)). EPS is therefore the current level of hazard and assigns a number between 0% and 100% to every region so defined, thus providing a unique measure. Physically, the EPS corresponds to an estimate of the level of progress through the earthquake cycle in the defined region at the current time.

Global Seismic Nowcasting With Shannon Information Entropy

“…We replace the counts of small earthquakes with the sum of the self‐information in magnitude space using equations and (see Rundle et al, ). Further, we assume that the coarse‐grained magnitude element is given by the typical magnitude resolution of Δ m ≈ 0.1.…”

Identifying the occurrence time of an impending major earthquake: a review

“…Seismicity is a typical example of complex time series, and earthquakes exhibit complex correlations in time, space and magnitude (M) which have been studied by several authors (for example see Huang 2008Huang , 2011Lennartz et al 2008Lennartz et al , 2011Rundle et al 2012Rundle et al , 2016. The observed earthquake scaling laws (e.g., Turcotte 1997) indicate the existence of phenomena closely associated with the proximity of the system to a critical point (e.g., Holliday et al 2006;Varotsos et al 2011c).…”

Earthquake Forecasting Using Artificial Neural Networks

“…Nowcasting is a surrogate method to find the current progression of occurrence of large earthquakes using the count of small events that occur between two large earthquakes. The definition of large magnitude earthquakes changes throughout the study (Rundle et al, 2016). We use different threshold magnitude in different experiments to define large earthquake events.…”