HR: 0830h
AN: S31F-0822 [PDF]
TI: Estimation of the average rate for subducting Pacific plate near Kamchatka related to earthquake
deformation
AU: * Gordeev, E
EM: gord@emsd.iks.ru
AF: Kamchatkian Department, Geophysical Service, Russian Academy of Sciences, av. Pijp, 9,
Petropavlovsk-Kamcha, 683006
Russian Federation
AU: Pavlov, V
EM: pvm@emsd.iks.ru
AF: Kamchatkian Department, Geophysical Service, Russian Academy of Sciences, av. Pijp, 9,
Petropavlovsk-Kamcha, 683006
Russian Federation
AB:
The Pacific plate moves toward the Euroasia plate at an average velocity of about 8 cm/year. This movement consists of the
deformation connected with subduction zone earthquakes and with slow deformation that can be the result of both creep on the
plate border and of viscous relaxation in the upper mantle. In order to know the role of slow deformation, it is need
necessary to estimate the deformation caused by earthquakes.
The average rate of the Pacific plate toward Euroasia related to earthquake deformation can be estimated from Harvard CMT
(Centroid Moment Tensor) catalog which has information for earthquakes with MwA4.5 for the East Coast of Kamchatka from 1976
to the present. From these earthquakes, we chose the initial time, hypocenter position, scalar moment M0 and strike, dip and
slip values. For the north, central and south parts of the Kamchatka subduction zone, we estimated the average strike and
dip value for all earthquakes. The values of the strike and dip for the south and central parts respectively ranged from
204"-237" and 11"-52". For the north part, related to the junction between the Kamchatkan and Aleutian arcs, the strike
and dip ranges are very large, which can be the result of a complicated fault system. For the south and central part, we
found average strike and dip values of 217" and 25" respectively. For this plane we calculated the average motion per year
for each area as follows:
B=M0i/ST0, where M0i = scalar seismic moment for ith earthquake, S = square of averaging, = shear module, T0 = time
of averaging. The shear module was estimated as: = C2/3, where C= 7km/c (velocity of P-wave), = 3 g/cm3, T0 = 20
years.
The B-value (rate of subduction related to earthquakes) was calculated as 0.9 cm/year for the south part of subduction zone
and 1.4 cm/year for the central part. For the north part, we are unable to make an estimation, because it was not found the
common plane (dip value) for all earthquakes.
These rate estimates don_t reflect the real ratio between slow or creep deformation and deformation released by earthquakes,
because of the limited time of observation. In the case of the central part of the subduction zone, however, we believe that
the rate in 1.4 cm/year is realistic, because an earthquakes of Mw = 7.9 occurred in this area on December 5, 1997.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 7209 Earthquake dynamics and mechanics
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting