Spatial distribution of earthquakes associated with the Pacific plate subduction off northeastern Japan revealed by ocean bottom and land observation
- 31 December 1992
- journal article
- Published by Elsevier BV in Physics of the Earth and Planetary Interiors
- Vol. 75 (1-3), 165-175
- https://doi.org/10.1016/0031-9201(92)90127-h
Abstract
Precise earthquake locations in the vicinity of a trench axis elucidate the characteristics of the shallower part of a subducting plate. We split the Japan Trench into two regions, off-Sanriku in the north and off-Fukushima in the south, on the basis of the seismic properties of the regions and the fine microearthquake structure investigated by ocean bottom seismographic surveys, as well as recent observation of major seismic activity. From ocean bottom seismograph data, the hypocentral distributions along a profile perpendicular to the trench axis, indicate that almost all earthquakes occur along the boundary separating the subducting Pacific plate and the landward plate. A difference of the hypocentral distribution between off-Fukushima and off-Sanriku is found at the shallow plate boundary level. The seismic thrust zone begins at more than 100 km landwards from the trench axis off-Fukushima, whereas it begins at 50 km off-Sanriku and is nearly flat between 50 and 100 km from the trench axis. This reflects regional variations of the interplate coupling. In spite of these variations, a common characteristic in recent observations indicates that in both regions almost all the hypocenters are deeper than 10 km. This suggests the plate boundary to be decoupled at least in the part shallower than 10 km.Keywords
This publication has 12 references indexed in Scilit:
- Earthquake distribution in the subduction zone off eastern Hokkaido, Japan, deduced from ocean-bottom seismographic and land observationsGeophysical Journal International, 1991
- Spatial distribution of earthquakes off Sanriku, northeastern Japan, in 1989 determined by ocean-bottom and land-based observation.Journal of Physics of the Earth, 1990
- Observations of microseismicity in the southern Kuril Trench area by arrays of ocean bottom seismometersGeophysical Journal International, 1989
- The origin of large or great thrust-type earthquakes along subducting plate boundariesTectonophysics, 1985
- A seismicity gap beneath the inner wall of the japan trench as derived by ocean bottom seismograph measurementTectonophysics, 1985
- Spatial distribution of microearthquakes beneath the Japan Trench from ocean bottom seismographic observationsGeophysical Journal International, 1983
- Double-planed deep seismic zone and upper-mantle structure in the Northeastern Japan ArcGeophysical Journal International, 1978
- Double-planed structure of the deep seismic zone in the northeastern Japan arcTectonophysics, 1978
- Structure of micro-earthquake activity around Japan trench, off Sanriku, obtained by ocean-bottom seismographic network observation.Journal of Physics of the Earth, 1976
- Source mechanisms and tectonic significance of historical earthquakes along the nankai trough, JapanTectonophysics, 1975