A Typical Foreshock and Aftershock Anomaly: Observations, Interpretation, and Applications

Abstract

Previous publications by this author (Rodkin, 2008a, 2008b, 2012; Rodkin and Tikhonov, 2016; Rodkin and Rundkvist, 2017) proposed and actually used a method for constructing and analyzing the generalized vicinity of large earthquakes (GVLE). The GVLE method provides an enormous increase in the amount of data that is used and, hence, a much more detailed description of the typical features in the foreshock–aftershock process. The GVLE clearly detects the power-law foreshock seismicity increase and the aftershock process obeying the Omori–Utsu law. In addition, many parameters (the slope of the recurrence plot and the average depths of focus, apparent stresses, the duration of the seismic process, and several other quantities) show, when treated in the GVLE framework, similar anomalies whose amplitudes are increasing toward the time of the generalized large earthquake minus the logarithm of the time remaining until the occurrence. Similar anomalies (more frequently with different parameters) are observed both in the foreshock area and in the aftershock area. Because the anomalies are so similar we are entitled to treat them as a seismicity pattern. Precursory anomalies are of special interest. We discuss the question of which of these are primary and which are secondary. The anomaly is interpreted in terms of the multiplicative cascade model. An analogy in the character of this anomaly with Zhurkov’s concept of kinetic failure exists. We discuss the approaches to the use of the anomaly in earthquake prediction.