Problems of Engineering Seismology: article

Аnnotation: We have been studying characteristics of short-period S wave attenuation field in the South-West Alaska lithosphere (in the Alaska subduction zone). Recordings of seismic station KDAK, obtained for shallow earthquakes within the distance range of ~250–750 km, were processed. We used a method based on an analysis of a ratio of maximum amplitudes in Sn and Pn waves (parameter Sn/Pn). Correlation dependence of this parameter on distance for wave lines, crossing rupture zones of three large and great earthquakes: Great Alaska one of 28/03/1964 (MW = 9.2), Simeonof one of 22/07/2020 (MW = 7.8) and Chignik one of 29/07/2021 (MW = 8.2) is constructed. It was established that this dependence goes a little higher of the analogous dependences, obtained earlier for the regions of southwest Japan and central Chile, and much higher than for the region of northeast Japan. The reasons for essential differences of these dependences in various regions are discussed. We consider heterogeneities of the attenuation field in the rupture zones of the Simeonof earthquake, its largest aftershock (MW=7.6), and also of the Chignik earthquake.