MIGRATION OF CRUSTAL DEFORMATION

Observations on the migration rates of crustal deformation, as recently discovered in several tectonic areas, such as the south Kanto and central Tohoku districts, Japan and the West Cordillera Mts., Peru, has opened up a new opportunity for the study of crustal dynamics. Briefly, these examples from coastal areas are characterized by migration landwards with a velocity of about 10-100 km/yr. This agrees well with the velocity of mIgration of seismicity as previously known. Dispersion and dissipation of the deformation waveform are also noted as characteristics. Simple extrapolation of the migration path back toward the ocean may locate a possible origin of the event. In the case of the south Kanto district, for example, the deformation front seems to have originated in the early 1950s from the vicinity of the junction of the Japan and Izu-Mariana trenches. The deformation front in the central Tohoku district, on the other hand, is thought to have originated in the northern part of the Japan Trench in the late 1960s. One may suppose that either a repeated irregular aseismic plate motion generates the deformation events, or that it results from a periodic seismic slip at a plate boundary. In the latter case, the 1953 Boso-oki and the 1968 Tokachi-oki earthquakes might be suspected of generating the deformation fronts in the south Kanto and central Tohoku districts respectively. As Scholz speculated, the migration of a deformation front might trigger earthquakes, if it hits areas of high seismic potential. Studies of migration events can contribute significantly to earthquake prediction studies. © 1979.