Item

Abstract

To gain new insight into patterns of earthquake activity in the Pacific Northwest we study regional seismic dynamics in terms of several moving averages. In particular, the variability of the Unified Scaling Law for Earthquakes (USLE) coefficients in 3D have been evaluated at the three separate seismic focal zones – Southern Kamchatka, Northern Kamchatka, and Commander segment of Aleutian arc. USLE states that the logarithm of expected annual number of earthquakes of magnitude M or larger in an area of linear dimension L follows within the magnitude range [M–,M+] the relationship logN(M,L)=A+B×(5−M)+C×logL, where A, B, C are empirical constants. Naturally, USLE compliments to a- and b-values of the Gutenberg-Richter relationship with C, an estimate of fractal dimension of epicentres at a given site. USLE allows for realistic rescaling seismic hazard to the size of exposure at risk and its scaling parameter η controls regional distribution of inter-event times. We considered shallow and intermediate depth earthquakes with magnitude M≥4.0 in 1996–2020 reported in the open access database of the Kamchatka Branch of GS RAS. The results show up distinct statistically significant differences in the southern and the northern segments of the Kamchatka slab as well as in the western segment of the Aleutian arc. The plots of the three USLE coefficients in 3D display their complex correlation patterns of different type in the preselected volumes of seismic genesis. The study is carried on in the framework of the Russian State Task of Scientific Research Works of IEPT RAS (0143-2019-0006).