Muography as a new tool to study the historic earthquakes recorded in ancient urial mounds

Abstract. Bidirectional muographic measurements were
conducted at the Imashirozuka burial mound, Japan. The
mound was built in the beginning of the 6th century as a
megalithic tomb and later collapsed after a landslide caused by
the 1596 Fushimi earthquake, one of the largest earthquakes
that has occurred in Japan over the last few centuries. The
measurements were conducted in order to find evidence of
this past disaster recorded in this historical heritage site. As a
result, the vertical low-density regions were found at the top
of the mound. These regions were interpreted as large-scale
vertical cracks that caused the translational collapse process
behind the rotational landslide that was already found in prior
trench-survey-based works. These results indicate that there
was an intrinsic problem with the stability of the basic
foundation of the Imashirozuka mound before the 1596 Fushimi
earthquake.

Hiroyuki K. M. Tanaka1,2, Kenji Sumiya3, and László Oláh1,2
1Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan
2 International Muography Research Organization (MUOGRAPHIX), The University of Tokyo, 1-1-1 Yayoi,
Bunkyo, Tokyo 113-0032, Japan
3 Graduate School of Informatics, Kansai University, 2-1-1 Ryozenji-cho, Takatsuki-shi, Osaka 569-1095, Japan
Correspondence: Hiroyuki K. M. Tanaka (ht@eri.u-tokyo.ac.jp)
Received: 30 April 2020 – Discussion started: 2 June 2020
Revised: 13 July 2020 – Accepted: 22 July 2020 – Published: 4 September 2020