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Abstract:
We continue analysing earthquake sequences in terms of their variability and scaling properties, including the behaviour of the control parameter η of the unified scaling law for earthquakes (USLE), along with a detailed analysis of the surface wave records for reconstruction of the source in approximation of the second moments of the stress glut tensor to obtain integral estimation of its length, orientation, and seismic process development over time. In particular, we present the analysis of the cases of the three recent earthquakes in Southern Alaska – 22 July 2020, Mw7.8 at 105 km SSE of Perryville, 19 October 2020, Mw7.6 at 97 km SSE of Sand Point, and 29 July 2021, Mw8.2 at 99 km SE of Perryville – that have occurred right at the western edge of the rupture zone of the 1964 Great Alaska, M9.3 mega-earthquake and contribute to apparent activation of the region started with the three major earthquakes (24 January 2016, Mw7.1, 23January 2018, Mw7.9, and 30 November 2018, Mw7.1) at its north-western and southern borders.
Due to yet rather small number of case studies, it seems premature to discuss if the observed quantitative characteristics of seismic variability and their scaling properties disclose clear patterns useful in operational earthquake forecasting of seismic catastrophes including the extreme mega-earthquakes. However, our studies give a new insight into better understanding of seismic dynamics in the Pacific Northeast.
The study is carried on in the framework of the Russian State Task of Scientific Research Works of IEPT RAS (0143-2019-0006, 0143-2019-0007).
