Seismic Intensities of the 1944 Tonankai Earthquake (M 7.9) (2) : Characteristics of Damage and Phenomena from Supplementary

Abstract

Earthquake Research Institute (ERI), The University of Tokyo conducted a questionnaire survey immediately after the 1944 Tonankai earthquake. By examining the 290 original questionnaire sheets, Harada et al. (2017) assessed 288 seismic intensity values on the Kawasumi intensity scale (KI-scale). In addition to questions to assess seismic intensity values, the questionnaire survey also requested respondents to make notes in the margins of sheets. In response, 81 questionnaire sheets provided supplementary descriptions, which are valuable because they were recorded by people who experienced the earthquake and suffered from it, and are important for revealing the behavior of seismic waves and the source mechanism of the 1944 Tonankai earthquake. All the supplementary descriptions are reprinted and descriptions of damage, water disturbances, ground deformations, and tsunamis are examined. As a result, the following characteristics are revealed: (1) Damage and ground deformations at high-seismic-intensity observation points are described on the questionnaire sheets. At several points, damage in supplementary descriptions is more severe than in questionnaire responses. Supplementary descriptions show damage was most serious in and around the Suwa Basin, probably due to local amplification of seismic waves in the basin. (2) Sloshing tank water in the Tokyo metropolis and Aichi prefecture was excited by 2-4 sec. period seismic waves. (3) Large-scale ground deformations occurred in the deltas around the river mouths of Kiso, Nagara, and Ibi Rivers in Aichi and Mie prefectures. Boiling soil and cracks due to liquefaction in Kumoi village caused by the 1944 Tonankai earthquake are the only records of liquefaction in Shiga Prefecture. (4) Although 1944 tsunami damage was serious, supplementary descriptions about the tsunami are limited probably because the ERI also conducted a tsunami questionnaire survey on the 1944 Tonankai earthquake