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

Apparent stresses of 105 moderate-sized (magnitude mb from 4.5 to 6.0) shallow earthquakes from the subduction zone near Kamchatka Peninsula (NW Pacific) were analyzed. Our results allowed us to formulate the f ollowing properties of the earthquake apparent stress for the seismic moment range 10(15) to 10(18) 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 differ ence of a factor of 3. (2) Average apparent stresses were greater in t he coastal zone near Kamchatka, where subducting oceanic and overridin g 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.