Tectonic Archaeology as a Foundation for Geoarchaeology

Tectonic Archaeology, 2022

Asian Perspectives, 2017

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

This is a summary by Dr. David Book (c) of my lecture on 15 June 2013 for the Harrow & Hillingdon Geological Society

In Sintubin, M.; Stewart, I.S.; Niemi, T.M.; and Altunel, E., eds. Ancient Earthquakes. Geological Society of America Special Paper 471, p. 81-96, 2010

Earthquake archaeology developed in Japan simultaneously with that in the Mediterranean in the mid-1980s. By 1996, evidence of earthquake occurrence had been documented at 378 sites throughout the archipelago. The main features identified include various results of liquefaction, faults, landslips, and surface cracking. This evidence differs greatly from the standard Mediterranean focus on building damage, and the reasons for the very different natures of archaeoseismology in these world regions are explained herein. This article recounts the development of this new subfield, inspired by the interest of geomorphologist Sangawa Akira and taken to its most recent advances in identifying soft-sediment deformation structures by geoarchaeologist Matsuda Jun-ichirō. The evidence of earthquake activity at archaeological sites can be matched with earthquakes caused by either active fault movement or subduction. The historical record of earthquake occurrence, already documented back to 599 C.E., is extended into the prehistorical record through relative dating of artifacts and features on archaeological sites. Both the identification and the dating of the archaeological evidence of earthquakes can be challenged, though the “territorial approach” gives the data a significance that is not achieved through analysis of single sites.

Pp.21-42 in "Environment and Society in the Japanese Islands", ed. by Philip Brown and Bruce Batten. Corvallis, OR: Oregon State University Press., 2015

The Journal of the Geological Society of Japan, 2014

Great earthquakes of M8 and above and accompanying tsunamis have repeatedly occurred in the Nankai and Sagami Trough regions. These events have caused severe damage to the coastal areas close to the troughs. As part of the response to the 2011 off the Pacific Coast of Tohoku Earthquake (or the Great East Japan Earthquake) and tsunami, the Cabinet office of the central Japanese Government proposed new guidelines for assessing the risk of similar earthquakes and tsunamis affecting the Nankai and Sagami Trough regions. These new guidelines call for the largest possible class of earthquake and tsunami to be taken into account even if the probability of such an event is low. Large earthquakes and tsunamis in this region would affect an area with high concentrations of population and industrial infrastructure. As a result of these changes, the last 2 years have seen a high public awareness of disaster mitigation measures in the region. One of the results has been that some local governments have begun upgrading their existing disaster prevention infrastructure, such as raising the height of existing dikes and reinforcing refuges to help protect the population in the case of future great earthquake and tsunami events. Paleoseismological studies have been carried out in the Nankai and Sagami Trough regions to help establish the recurrence history of great earthquakes and tsunamis. The sources of information are both historical documents and tsunami deposits. However, our present level of knowledge remains insufficient to be able to confidently reconstruct the size and recurrence intervals of past earthquakes and tsunamis. This information is key to developing predictive models for the timing and size of future events as well as formulating disaster prevention measures, and there is a need for more studies. In this excursion, we will visit historical sites that preserve evidence for past natural disasters and geological sites that preserve records of seismic-related uplift and great tsunamis. We will also observe the current state of tsunami disaster mitigation measures, such as the plan for tsunami evacuation, in Shizuoka Prefecture. Through this excursion, we also hope to offer the participants an opportunity to discuss the significance of geological information in paleoseismology, to assess its importance in informing and guiding plans for disaster mitigation and to explore likely future trends in the field of paleoseismology.

Handbook of East and Southeast Asian Archaeology, 2017

Japanese Archaeology Today: New Developments, Structural Undermining, and Prospects for Disaster Archaeology

The earthquake that struck Japan on 11 March 2011, named the Great East Japan Earthquake by the Japanese government, was one of the largest seismic events the world has seen for generations. Akira Matsui reported his experience of visiting the areas devastated by the earthquake and tsunami soon afterwards, outlining the initial assessment of damage caused to museums and cultural heritage assets, and the plans for their rescue (Kaner et al. 2011; Matsui 2011a). The present contribution reports how far the implementation of these plans has been successful, the prospects for the future, and situates all of this in a broader context of archaeological response to earthquakes. This is not the first time that Japan has been obliged to address these matters. Within recent memory, the Great Hanshin Awaji Earthquake, which struck the city of Kobe and the surrounding region in 1995, resulted in the loss of more than 5000 lives and caused immense damage to cultural heritage. A systematic rescue of cultural heritage assets, including archaeological sites, was then organised. The fact that Japan has experienced two major earthquakes within just 16 years compels us to start thinking seriously as to what we as archaeologists can do to prepare for future disasters of equal magnitude. In this globalised world, we also feel strongly that our experience, and what we have learnt, should be shared with colleagues the world over.

The AD 1498 Meio earthquake (M8.2∼8.4) that occurred along the eastern Nankai trough, and the tsunami generated by the earthquake, induced major geomorphological and social changes along the Pacific coast of central Japan. Geological coring along the palaeochannel of the Hamana River, southern Shizuoka Prefecture, revealed that its river mouth was abruptly closed followed by a rapid change from river to marsh environment at the end of the 15th century. It is suggested that mass transport of sediments by the Meio tsunami forced the closure of the river mouth. The latter environmental change happened synchronously with the sudden decline of a famous port town, Hashimoto, formerly flourishing along the middle reach of Hamana River. Closure of the water route connecting Hashimoto with the Pacific Ocean potentially led to the decline and abandonment of the port town.

Earth-Science Reviews, 2016

The Nankai-Suruga Trough, the subduction zone that lies immediately south of Japan's densely populated southern coastline, generates devastating great earthquakes (magnitude > 8) characterised by intense shaking, crustal deformation and tsunami generation. Forecasting the hazards associated with future earthquakes along this >700 km long fault requires a comprehensive understanding of past fault behaviour. While the region benefits from a long and detailed historical record, palaeoseismology has the potential to provide a longer-term perspective and additional crucial insights. In this paper, we summarise the current state of knowledge regarding geological evidence for past earthquakes and tsunamis along the Nankai-Suruga Trough. Incorporating literature originally published in both Japanese and English and enhancing available results with new age modelling approaches, we summarise and critically evaluate evidence from a wide variety of sources. Palaeoseismic evidence includes uplifted marine terraces and biota, marine and lacustrine turbidites, liquefaction features, subsided marshes and tsunami deposits in coastal lakes and lowlands. While 75 publications describe proposed evidence from more than 70 sites, only a limited number provide compelling, well-dated evidence. The best available records enable us to map the most likely rupture zones of twelve earthquakes that occurred during the historical period. This spatiotemporal compilation suggests that the AD 1707 earthquake ruptured almost the full length of the subduction zone and that earthquakes in AD 1361 and 684 may have been predecessors of similar magnitude. Intervening earthquakes were of lesser magnitude, highlighting the variability in rupture mode that characterises the Nankai-Suruga Trough. Intervals between ruptures of the same seismic segment range from less than 100 to more than 450 years during the historical period. Over longer timescales, palaeoseismic evidence suggests intervals between earthquakes ranging from 100 to 700 years, however these figures reflect a range of thresholds controlling the creation and preservation of evidence at any given site as well as the genuine intervals between earthquakes. At present, there is no geological data that suggest the occurrence of a larger magnitude earthquake than that experienced in AD 1707, however few studies have sought to establish the relative magnitudes of different earthquake and tsunami events along the Nankai-Suruga Trough. Alongside the lack of research designed to quantify the maximum magnitude of past earthquakes, we emphasise issues over alternative hypotheses for proposed palaeoseismic evidence, the paucity of robust chronological frameworks and insufficient appreciation of changing thresholds of evidence creation and preservation over time as key issues that must be addressed by future research.