The Large (<i>M</i> ≥ 6.0) Earthquakes Seismic Precursors in the Junction Zone of the Kuril-Kamchatka and Aleutian Island Arcs

Abstract

The article describes the behavior of the series of seismic precursors before the activation of 2016‒2019 in an area with a tectonically complex geodynamic environment at the boundaries of the Pacific, North American, and Eurasian lithospheric plates. In order to clarify the location of possible focal areas of future strong earthquakes, a comprehensive approach to the application of allocated precursors was considered: quiescence by parameters RTL and Z-function, variations of the slope of the recurrence graph γ and areas of seismic ruptures dS. For the first time, in relation to Kamchatka, for anomalies to parameter dS, interpreted as seismic activations, the presence of a predictive component before the onset of foreshock activation is shown by the example of an increase in its values before the events that are the strongest for the areas where their focal areas are located: the Near islands Aleutian earthquake with Mw = 7.8 on July 17, 2017 and the Uglovoye Podnyatiye earthquake on December 20, 2018, Мw = 7.3, is demonstrated. The total length of the anomalous region, currently existing and including successive stages of quiescences and foreshock activations is ~900 km, which allows for the possibility of a new strong earthquake with a magnitude exceeding all previously recorded in this area in the junction zone of three lithospheric plates.