The Search for Tsunami Evidence in the Geological and Archaeological Records, With a Focus on Japan
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The Search for Tsunami Evidence in the Geological and Archaeological Records, With a Focus on Japan
abstract

Tsunami damage to archaeological sites in Japan has been recognized since the 1980s, but the Great Tōhoku-oki Earthquake and tsunami of 11 March 2011 stimulated geologists and archaeologists to find evidence of previous tsunami in Japan, investigate the responses of earlier inhabitants to tsunami, and assess the probability of future occurrences. Excavated sites on the Sendai Plain, partially inundated in this recent tsunami, have been crucial in this endeavor, with recovered data at times contradicting historical sources. Great progress has been made in the science of identifying tsunami deposits and understanding their nature and distribution, aiding in their recognition at archaeological sites. This article provides an introduction to the nature of tsunami waves and their causes, resources available for studying past tsunami worldwide, and difficulties in identifying tsunami sediments. Seventeen case studies of sites where tsunami deposits have been investigated throughout the Japanese and Ryukyu archipelagos are presented. Tsunami can be included within my conception of ‘tectonic archaeology,’ archaeology that must methodologically deal with the influence of plate tectonics on the islands. Earthquakes, volcanoes, and most tsunami relate to the subduction zone setting of Japan; thus, to fully understand the site remains of previous tectonically derived disasters demands knowledge of plate tectonics, seismology, volcanology, sedimentology, and wave physics among others. Integrating these spheres of knowledge into archaeological research opens new avenues of interpretation, including understanding why many Middle Yayoi settlements on the Sendai Plain were abandoned, not to be reoccupied for 400 years.

Keywords

tsunami, Japan, tsunami archaeology, Japanese archaeology, disaster archaeology, tectonic archaeology

from tectonic archaeology to disaster archaeology

Given the placement of the Japanese islands across four tectonic plates separated by two plate subduction zones, it is hardly surprising that tectonic forces have acted on past as well as present inhabitants (Barnes 2015a). Earthquakes, volcanic eruptions, and most tsunami have tectonic origins. The first two of these have given [End Page 132] rise to specialist archaeological subdisciplines in Japan: jishin kōkogaku 地震考古学 or Earthquake Archaeology was named by geomorphologist Sangawa Akira (Sangawa 1988) and kazanbai kōkogaku 火山灰考古学 or TephroArchaeology was coined by two volcanologists Arai Fusao and Machida Hiroshi (Arai 1993). A third may well be developing: tsunami kōkogaku 津波考古学, or Tsunami Archaeology, in parallel with the new field of Tsunami Geology (Goto et al. 2014). After the earthquake and tsunami event of 11 March 2011 in Japan, the Tōhoku Tsunami Joint Survey Group was formed, involving more than 300 Japanese and international geologists and engineers (Sato 2015). Although their purposes differ, geologists and archaeologists often work on the same sites or in collaboration to identify past tsunami (e.g., Ogura 2016). Geologists usually assess risk for damage mitigation, while archaeologists investigate past human responses to tsunami.1

There is now a movement in Japan to combine these interrelated subdisciplines into a more encompassing Disaster Archaeology that goes beyond tectonic causes to include all sorts of natural disasters (Okamura 2015; Okamura et al. 2013; Saino 2012b). A Disaster Archaeology database compiling information from published site reports is currently being developed at the Nara Research Institute for Cultural Properties (Nara Bunkazai Kenkyūjo, abbreviated as Nabunken) (Okamura 2015:251). These efforts at database construction by Nabunken close the circle on Shimoyama’s attempts in the late 1990s and early 2000s to promote the field of Disaster Archaeology and present on the archaeology of natural disasters at World Archaeology Congresses (WAC4 in 1999,WAC5 in 2003) (Shimoyama 1997, 2002a, 2002b; Torrence and Grattan 2002). These newly developing subdisciplines contrast with Gould’s (2007) proposal to deal with current disasters and recover data from them by aligning with forensic anthropology. Meanwhile, Schlanger, Nespoulous, and Demoule (2016) distinguish “disaster-led archaeology” from “developer-led archaeology.” Although both these approaches fall into the realm of “rescue” (a.k.a. “preventive”) archaeology, the former refers to the dramatic increase in archaeological excavations necessitated by recovery and re-building efforts. Archaeologists also bear the burden of preserving the memory of natural disasters for future generations in the form of disaster museums.

Shimoyama (2002a...


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