Vol.2 No.2 2009

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Research paper : A study of paleoearthquakes at archeological sites (A. Sangawa)−93−Synthesiology - English edition Vol.2 No.2 (2009) AuthorAkira SangawaCompleted doctorate course at the Graduate School of Science, Tohoku University in March 1979 (Doctor of Science). Joined the Geological Survey of Japan, Agency of Industrial Science and Technology, Ministry of International Trade and Industry in April 1979. Chief researcher of AIST from April 2001. Visiting researcher of AIST from April 2007. Also served as visiting professor at the Institute of Industrial Sciences, the University of Tokyo from April 2002 to March 2004, and visiting professor at the Disaster Prevention Research Institute, Kyoto University from April 2005 to March 2008. Engages mainly in research on active faults, and has been engaging in interdisciplinary research with archaeology since declaring earthquake archaeology in 1988. Received the Award of the Minister of Agency of Science and Technology in 2000.Discussion with Reviewers1 Activities to diffuse “earthquake archaeology”Question and Comments (Eikichi Tsukuda, Research Coordinator, AIST)The research of Dr. Sangawa is widely known throughout society, has received the attention of the mass media, and I think much contribution was made in reducing earthquake disasters. Earthquake study is rapidly advancing in recent years, but for the results to be returned to society as Full Research, and to actually reduce earthquake damages, increased understanding of the general public about earthquakes is necessary, and it must result in both long-term activities (earthquake resistant residences) and short-term activities (immediately after an occurrence of an earthquake). I think Dr. Sangawa’s research, as a Full Research, is an extremely important contribution in the field of earthquake disaster reduction. Can you please provide comments about the diffusion activity through your experience in collaboration with the mass media?Answer (Akira Sangawa)As you indicated, I think diffusion through the mass media is important. Although lectures and writings by researchers can transmit specialized knowledge to the general public, there is an enormous difference in the capacity to reach many people through newspapers, TV, and radio. In that sense, the mass media plays the role as a bridge between the researchers and the general public, and is important in widely publicizing the research results. When there is coverage, I try to provide sufficient explanation so my intent is communicated accurately, and specialized knowledge is explained where needed to make the contents of coverage as high quality as possible. I think the people of AIST, particularly of the Geological Survey, who are involved in earthquake research, respond very carefully to news interviews.As long as we live in Japan, there is a chance that our lives may be lost due to an earthquake, and it is necessary for all Japanese citizens to have at least some knowledge of earthquakes. However, not too many people seek this knowledge actively. I think it is important to engage in diffusion to people who think earthquakes are too difficult for them to understand. As one method, I talk in terms of subjects that the general public find interesting. It is more effective if earthquakes are coupled with cultural properties such as tombs and famous historical events. 2 Synthetic process of “earthquake archaeology”Question and comment (Akira Ono, Vice President, AIST)I think this is an excellent research where archaeology and seismology were fused to successfully create a new discipline. Can you please explain, using diagrams if possible, how a new fused discipline was created from two different disciplines?Answer (Akira Sangawa)I created Fig. a. Although it is a fusion of archaeology and seismology, seismology mainly utilizes geologic methodology, so I added “geology” in small type under seismology in the figure on the left.In the survey of archaeological sites, excavation is done from the ground surface downward to dig up the remains and artifacts, dates are figured out using archaeological methods, and comparisons made with ancient records and writings. As a result, new findings can be added to the history of the region.In seismology, the fields involved and methodologies are diverse, so I listed the research subjects in Fig. a. The subjects are: places where the earthquake occurs like plate boundaries and active faults; also, events that occur due to an earthquake such as liquefaction and landslides. Advancements of both researches are necessary for earthquake prediction and damage reduction.Earthquake archaeology begins when a trace of an earthquake is found at an archaeological site. The date of the earthquake trace is obtained using the dates of remains and artifacts, and such materials are accumulated to build a history of earthquakes. Recently, the study of the history of active faults has progressed, and we find many earthquake traces that correspond to fault activities. Each earthquake history of plate boundaries and active faults becomes basic material for predicting future occurrences. On the other hand, observation of sand flow and movement brings new findings about liquefaction. The traces of landslide in structures whose original shape are known, as in a tomb, help clarifying the mechanism of landslides.In archaeology, earthquake traces used to be meaningless, mysterious things. Some of the mysteries of archaeology, such as the disappearance or the decline of a village after the date earthquake traces were left, the discovery of remains that show evidences of residences from lake bottoms, and the presence of strangely shaped tombs can now be solved by introducing the concept of earthquakes. In the case where there are abundant earthquake traces and the overall picture of earthquakes can be readily seen, as in the Tsukushi Earthquake of 679 and the Keicho Fushimi Earthquake of 1596, the earthquake traces provide exact dates and help refine archaeological dating.3 Traces of earthquakes other than liquefactionQuestion and comment (Akira Ono)In this paper, liquefaction is mainly described as a trace of great earthquakes on archaeological sites, but are there other kinds of traces?Answer (Akira Sangawa)In archaeological surveys, many traces of liquefaction in particular are found readily. Liquefaction occurs in the soft sand layer with abundant underground water. Our ancestors lived mainly in the plain with abundant water supply, so the traces of [31][32]T. Kamai: Kazumayama kofun no kisojiban to jishin oto kaiseki (Foundation of Kazumayama Tomb and earthquake response analysis), Kazumayama Kofun Hakkutsu Chosa Hokoku-sho (Report of Excavation survey at Kazumayama Tomb), 97-100 (2007) (in Japanese).M. Mimura and T. Ishizaki: Funkyu no doshitsu / jiban chosa (Survey of soil and ground of tomb mound), Takamatsuzuka Kofun No Chosa (Survey of Takamatsuzuka Tomb), Nara National Research Institute for Cultural Properties, 40-43 (2006) (in Japanese).

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