Crust and uppermost mantle structure beneath central Japan inferred from receiver function analysis

Toshihiro Igarashi,Tomotake Ueno,Takashi Iidaka,Takaya Iwasaki,Takuo Shibutani

doi:10.1186/bf03352974

Toshihiro Igarashi, Tomotake Ueno + Show 3 more

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https://doi.org/10.1186/bf03352974

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Abstract

Abstract We apply the receiver function method to estimate the structure of the crust and the uppermost mantle at an area that traverses central Japan including the Niigata-Kobe Tectonic Zone (NKTZ). The resultant receiver function images show clear seismic discontinuities, such as the subducting Philippine Sea plate, the Moho in the overriding plate, and other discontinuities inside the crust around the NKTZ. We also address station corrections for shallow structures using a synthetic receiver function. Crustal discontinuities seem to be complicated at the south side from the northern limit of the NKTZ. The dip of the discontinuities changes around the Atotsugawa active fault located in the NKTZ. The Moho discontinuity in the overriding plate is continuous and gradually dips to the south. The depths of the Moho discontinuity in the receiver function image exceed 40 km at the southern part of the profile line, and are 5–10 km deeper than that indicated by an explosion analysis of the same profile line. It seems that the differences between the estimated depths obtained by the two methods indicate complicated structures around the Moho discontinuity.

Highlights

Inland earthquakes occurring at active faults near urban areas threaten our safety, even if their magnitudes are middle-sized
The Niigata-Kobe Tectonic Zone (NKTZ) is a high strain rate zone extending from Niigata to Kobe, which was recently identified from analyses using a spatially dense GPS network (e.g., Sagiya et al, 2000) (Fig. 1)
We estimated the seismic discontinuities of the crust and the uppermost mantle in central Japan using the receiver function method with altitude and low-velocity sediment layer correction

Summary

Introduction

Inland earthquakes occurring at active faults near urban areas threaten our safety, even if their magnitudes are middle-sized. Many models have been proposed to explain the causes of the high strain rate at the NKTZ (e.g., Shimazaki and Zhao, 2000; Iio et al, 2002; Hyodo and Hirahara, 2003; Yamasaki and Seno, 2005) This zone is interpreted to be the inland plate boundary of the Japanese Islands (e.g., Heki and Miyazaki, 2001; Miyazaki and Heki, 2001) or an internal deformation zone forming the Japanese Islands (Mazzotti et al, 2000; Iio et al, 2002; Yamasaki and Seno, 2005). In spite of such differences of interpretation, most researchers think viscosity

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