Outcrop-scale characteristics of terrestrial tsunami deposits are non-uniform, because of their diversified grain-sizes, thickness and sedimentary structures. Grain-sizes of tsunami deposits are influenced a great deal by that of source area. Therefore some tsunami deposits may be composed mainly of mud and others gravel, and may be accompanied by boulders (Figs. 1-4). Grain-sizes of tsunami deposits also vary according to some factors such as the distance from the source area, even if they were made by the same tsunami in the same area (Figs. 1, 2, 4). Their thickness varies from a few millimeters to a meter or more. Some tsunami deposits are massive but others show a variety of sedimentary structures. These include parallel lamina, grading structure, inverse grading structure (Figs. 1, 2, 3), rip-up clasts (Fig. 2) and multiple graded units that reflect several wave inundation (Nanayama and Shigeno, 2006).Some sedimentary processes other than tsunami can form many of these characteristics. Therefore, it is required to exhibit as many criteria as possible along with fossil content and geochemical proxies when we identify paleo-tsunami deposits in strata.

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Tsunami geology has been attracted attention after the 2011 Tohoku-oki tsunami and it is now directly linked to the national and local disaster mitigation plans. This paper reviews the response of the sedimentologists after the 2011 Tohoku-oki tsunami and the new findings observed through the emergency response surveys, and then discuss the future perspective of the tsunami geology research. Unfortunately, the sedimentological surveys were not well organized because of the confusing situation soon after the earthquake and tsunami disasters. Nevertheless, there are many important findings in terms of the relationship between the tsunami inundation distance and the maximum extent of the sediments, sediment sources, and geochemical estimation of the tsunami inundation distance. In order to understand the paleo-tsunami deposits, understanding of the tsunami deposits that were formed by the recent tsunami is very important and hence we must continue to correct the data through the emergency response surveys soon after the forthcoming tsunami events. For future emergency response surveys, sharing the survey information and organization of the survey teams by the related societies are required for the efficient correction of the field data. Tsunami geology needs to be improved with collaboration of the engineers and disaster scientists in the future. In addition, geoscience is required to be included in the disaster prevention education because the low-frequency large tsunami is occurred well beyond the human life span and hence it is very difficult to imagine for the public people for such events without the proper education.

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The papers which include recognitions of sandy tsunami deposits are compiled to review the criteria used by authors to distinguish tsunami deposits. They are classified as follows; (1) wider distribution of sand layers, (2) agreement with historical tsunami events, (3) sedimentary structures, (4) coincidence to tectonic uplift/subsidence, (5) grain components peculiar to tsunami. It is important to describe modern tsunami deposits for appropriate recognition of paleotsunami deposits, but we need to consider the preservational possibility and the different coastal conditions between modern and past. For the present there is no single almighty criteria so combinations of several criteria is necessary depending on sedimentary conditions.

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After the 11 March 2011 Tohoku-oki tsunami, tsunami geology has been attracted attention from the public in the World. Tsunami boulders are also an important marker of the low-frequency large tsunami and hence they are useful for the tsunami risk assessment. This paper focuses on the current progress and future perspective of the tsunami boulder research based on the recent studies. After 2009, reports of the tsunami or storm wave boulders have increased and the understanding of their natures are well improved. Moreover, number of theoretical and numerical analyses for the identification and transport process of boulders have been performed. However, there have been yet no universal criteria to identify the tsunami boulders sedimentologically and theoretically. The reports of the Japanese tsunami boulders are still very limited except for the studies at the Ryukyu Islands, probably because the field survey intended to find the coastal boulder deposits has not been performed along the coast in other area. Tsunami boulders are useful evidence of the historical and prehistoric tsunamis at the places where rocky platform or coral reefs exist at the shore. Further researches to establish the identification criteria of tsunami boulders and the methodology for the risk assessment are indeed required for future risk assessment around the coast of Japan.

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Huge damages occurred along the Pacific coast of Tohoku by the 2011 off the Pacific coast of Tohoku earthquake. The preliminary results on submarine investigations after the earthquake indicate the wide distribution of the event deposits by the earthquake and/or its related tsunami. Characterization of the event deposits and consideration of their depositional processes is very important to understand what happen at sea floor by the particular earthquake, and to recognize the past earthquake- and/or tsunami-induced offshore deposits. Therefore, sedimentological and geological investigations at the offshore of Sanriku-Sendai coast from coastal shallow water to the Japan Trench should be conducted to clarify the depositional processes and temporal changes of the event deposits. Integration of results of the investigations with the simulation and experimental studies is also important.

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Sediment transport due to tsunamis causes various damages, e.g., salt damage, destruction of coastal protection facility, shoaling navigation channel in port, blocking water intake in power plant. These damages are extended over a long period and hamper rescue and restoration. On the other hand, tsunami deposits include valid information on historical and prehistoric tsunamis, and so they are useful for tsunami risk assessment. For the tsunami disaster mitigation purpose, the numerical model on tsunami sediment transport becomes essential recently. In this paper, the numerical model is reviewed and its problems are discussed.

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