Influence of source directivity and site effects of 2003 Tokachi-oki earthquake on the generation of high PGA in the near-fault zonesстатья
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Дата последнего поиска статьи во внешних источниках: 26 июня 2024 г.
Аннотация:We study source directivity and site efects of 2003 Tokachi-oki earthquake (Japan, Mw ~ 8.3) andtheir infuence on the distribution of peak ground accelerations (PGA) in the near-fault zones arestudied. Based on records of KiK-net vertical arrays, models of soil behavior are constructed, i.e. vertical distributions of stresses and strains induced in soil layers by strong motion. We use the method of Pavlenko and Irikura (2003), previously applied for studying soil behavior during 1995 Kobe, 2000 Tottori, and 2011 Tohoku earthquakes. During the Tokachi-oki earthquake, we did not find a widespread nonlinearity of soft soil behavior. Manifestations of soil nonlinearity were observed at sites closest to the source; at remote sites where high PGA were recorded, soil behavior was virtually linear, and shear moduli in soils increased till the moments of the highest intensity of motion, then decreased. The shapes of acceleration time histories at remote sites indicate directivity efects: seismicwaves radiated by the crack tip during its propagation along a section of the fault plane came to the stations simultaneously. Soil hardening occurred at these sites that increased amplifcation and PGA on the surface. Similar efects were observed during 2011 Tohoku earthquake; evidently, they can occur during future strong earthquakes.