APPARENT STRESS OF EARTHQUAKES WITHIN THE SHALLOW SUBDUCTION ZONE NEAR KAMCHATKA PENINSULA

Abstract

Apparent stresses of 105 moderate-sized (magnitude m9 from 4.5 to 6.0) shallow earthquakes from the subduction zone near Kamchatka Peninsula (NW Pa-cific) were analyzed. Our results allowed us to formulate the following properties of the earthquake apparent stress for the seismic moment range 1015 to 1018 N-m and the focal depth range from 0 to 60 km: (1) Apparent stresses depend on the fault nature of earthquakes; they are greater for thrusts and smaller for normal faults, a difference of a factor of 3. (2) Average apparent stresses were greater in the coastal zone near Kamchatka, where subducting oceanic and overriding continental plates interact (2.5 MPa) and just under the trench axis (2.9 MPa), but lower in near-trench zones on the western slope of the trench (0.4 MPa); this difference is a factor of 6.