The detection of hidden iron items in a natural sand beach based on magnetic survey: an example at Yayorigahama Beach in Okayama Prefecture, Japan

川村紀子, 畠山唯達, 北原優

In order to detect buried iron items in a natural sand beach, we conducted a magnetic
survey with an Overhauser magnetometer. First, a three-meter—long survey line was laid at
Yayorigahama Beach in Okayama Prefecture. A steel can, a stainless steel knife, and a
plug-in multi-tap were buried at 10 cm. Magnetic field intensity (MFI) and the magnetic
susceptibility (MS) were measured on the beach surface. The MS values indicate a rela-
tively higher value at the site where the steel can was buried 10 cm in burial depths, while
such an increase was found at the depths of 20 cm, 30 cm, 40 cm and 50 cm. The peak of
MFI could be recognized at the depths of 10 cm to 40 cm. This implies that the MFI test
with an Overhauser magnetometer is more effective than the MS measurement. Magnetic
anomalies of MFI were recognized on another survey line in Yayorigahama Beach where
reinforcing iron bars were found at a depth of 90 cm. Our results indicate that the hidden
iron items could be detected using an Overhauser magnetometer in the sand beach

日本法科学技術学会誌

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https://doi.org/10.3408/jafst.846