Diffusion of crustal deformation from disturbances arising at plate boundaries—a case of the detachment beneath the Izu Peninsula, central Honshu, Japan—

Kana Takahashi,Tetsuzo Seno

doi:10.1186/bf03351873

Kana Takahashi, Tetsuzo Seno

Open Access

https://doi.org/10.1186/bf03351873

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Abstract

Abstract We carry out numerical simulation of disturbance propagation within a plate floating over a viscous layer based on the 2-dimensional equations of Lehner et al. (1981). We apply the results to the anomalous crustal movements in central Honshu that followed the dike intrusion event between Miyakejima and Kozushima in the mid of 2000. We assume that the anomalous crustal movements represent diffusive transfer of a slip on the detachment beneath the Izu Peninsula, that occurred at the time of the dike intrusion event, over thin viscous layers such as the fault gouge of nearby great interplate earthquakes (Seno, 2005). From the arrival times of the disturbance in the Tokai district, the diffusion coefficient is determined to be 50–150 m2/s, and the viscosity of the fault gouge to be 1013–1015 Pa s. This value of viscosity is significantly smaller than that of the asthenosphere, and would probably be caused by the elevation of pore fluid pressure close to the lithostatic in the rupture zones of nearby great earthquakes. The serpentinized wedge mantle landward of the rupture zones may also constitute part of the thin viscous layers.

Highlights

Migration of crustal deformation has been discovered in subduction zones by tilt- and strainmeters. Yamada (1973), for example, compared tilts at two adjacent stations in the S
We ignore the 3-dimensional complexities of the plate and plate interface structures such as the 20 km depth of the detachment beneath the Izu Peninsula. We admit that this might be oversimplification for such a place where transition from collision to subduction occurs, the purpose of this study is to show a possibility of diffusive transfer of crustal deformation for the anomalous displacements in central Honshu shown in Fig. 3, and not to mimic exactly the observed displacement field
If the value of viscosity is 1019 Pa s, diffusion over a distance of 10 km will take 103–104 years and the anomalous crustal deformation will not be seen in central Honshu

Summary

Introduction

Migration of crustal deformation has been discovered in subduction zones by tilt- and strainmeters. Yamada (1973), for example, compared tilts at two adjacent stations in the S. Migration of crustal deformation has been discovered in subduction zones by tilt- and strainmeters. Ishii et al (1980), using a strainmeter array in northern Honshu, Japan, suggested a migration of the strain to the northwest with a velocity of ∼40 km/yr. Turkey, a series of major earthquakes migrated at a velocity of 60–70 km/yr (Mogi, 1968; Toksoz et al, 1979). Another example was recognized in the NW Pacific subduction zones where seismicity migrated with a velocity of 150–270 km/yr (Mogi, 1968)

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