[S04-P] Poster

[S04-P-03] What age distributions of stone lanterns tell about historical earthquakes?: case studies at three sites in Japan

^○Mamoru Kato, Jun Hioka (Kyoto University, Kyoto, Japan)

Strong ground motion often topples stone lanterns, small stone objects standing in precincts of Japanese temples and shrines, which are observed in recent large earthquakes in Japan. Topple of stone lanterns occurs when the ground shaking is equal to or larger than JMA Intensity 5, which is roughly equivalent to MM Intensity 7. Descriptions of similar damage are found in historical documents, and have been used to estimate seismic intensities of historic ground motion. Design and size of old stone lanterns are similar to those of modern ones, which makes them practical sensors of ground motion at least for last 500 years. It is a customary practice to engrave the date of dedication in the stone lantern and we can identify stone lanterns which have experienced major historical earthquakes. This means stone lanterns as a group are records of historical earthquakes and in this study we explore what we can learn from such non-textual materials. Increase/decrease of stone lanterns frequently occur by anthropogenic or religious reasons, and quality of data is essential in identifying effects of earthquakes. We surveyed stone lanterns at three sites: Kitano-Tanmangu Shrine, Kyoto, Iwashimizu-Hachimangu Shrine, Yawata, and Zenkoji Temple, Nagano. These three sites are known for historical large earthquakes and a large numbers of stone lanterns in their small precincts. We are able to identify that historical earthquakes has weak effects on age distributions of stone lanterns. Among our findings are that very large earthquakes apparently wiped out stone lanterns in early years, and that dedication of stone lanterns apparently increases a few years after the earthquake, an indication of recovery from the disaster. It is difficult to estimate severity of historical ground shaking from stone lanterns.