Geophysical survey of Hirui-Otsuka Mounded Tomb in Ogaki, Japan

Abstract

The Hirui-Otsuka mounded tomb located in the city of Ogaki, Gifu Prefecture, Japan, is one of the largest keyhole-shaped mounded tombs in the Tokai region. Archaeological investigations of this tomb have been carried out continuously since 1994. Some of the geophysical methods were adopted in this investigation on the basis of a remarkable concept of ‘sensor fusion’. In this paper, the results of the geophysical surveys are presented. Ground-penetrating radar (GPR) survey and resistivity survey were applied in order to find the missing moat and to determine the boundary of this tomb. The GPR time-slices have shown clearly the outline of the missing moat and this was consistent with the excavation results. However, the apparent resistivity map has shown a different result. Radar and magnetic surveys were carried out on top of the mound in order to acquire information about the tomb's central burial. In this investigation, a newly developed frequency modulated continuous wave (FMCW) radar was used as well as a conventional pulse radar system. The magnetic survey was undertaken using a three-component fluxgate gradiometer. The GPR survey on top of the circular part of the mound revealed a 10 m by 10 m rectangular burial pit in the middle of which was a pit-style stone chamber about 6 m long by 2 m wide. The geomagnetic survey produced no archaeological information owing to the presence of numerous strongly magnetized obstacles near the surface of the area surveyed. Copyright © 2000 John Wiley & Sons, Ltd.