Changes in Earthquake Source Properties across a Shallow Subduction Zone: Kamchatka Peninsula

This paper studies the source properties of earthquakes originating within the shallow subduction zone near Kamchatka Peninsula. We use the regional catalog of 1962–1993 Kamchatkan earthquakes completed by the Institute of Volcanology, Russia. Our previous investigations (ZOBIN, 1990, 1996a) and this study allow us to show a gradual change in source properties of earthquakes from trench to coast. It was demonstrated that the swarm sequences change to the mainshock–aftershock sequences from trench to coast. The source area of aftershock sequences is generally smaller than the swarm areas for the same magnitude Ms of the mainshock or clue event of the swarm. Study of the Ms–Ks relation, where Ks is the energy class for Kamchatka earthquakes, reveals that the events radiate relatively higher frequencies from trench to coast.