Tsunami deposits: Present knowledge and future challenges

Abstract

Tsunami deposits are the primary source of information on (past) large tsunami events and thereby are crucial for accurate hazard assessments. Tsunami deposits studies have developed over the last three decades, but this is still a young geoscience discipline. Following the 5th International Tsunami Field Symposium in 2017 an opportunity arose to publish a Special Issue focusing on present knowledge and future research challenges. This paper aims to briefly review current state‐of‐the‐art research, summarizing major findings and gathering relevant works that describe the progress achieved over the last three decades. In this paper the relevance of tsunami deposits, their peculiar sedimentary characteristics and their differentiation from other high energy events are presented. Especially over the last decade an incredibly high number of studies have been published on tsunami deposits, many of which are of a high quality and provide detailed literature reviews. Some of these studies represent the current progress discussed here. Challenges are also introduced, to spur a discussion on future scientific questions that can and should be addressed by tsunami geoscientists. Coupling onshore–offshore records is an area where tsunami geoscience faces some of its major challenges. Moreover, the application of non‐destructive high‐resolution techniques to study the internal structure and composition of tsunami deposits can also provide an opportunity to further examine deposits, and from this derive physical parameters of the forcing mechanism. Another topic is better understanding of the erosional signature of tsunami events and a continuation of the effort to better incorporate age‐estimation methods by developing more accurate dating methodology. Finally, there is also the need for the improvement of empirical, forward and regressive numerical models to better contribute to the characterization of tsunami events.

A tsunamigenic delta collapse and its associated tsunami deposits in and around Lake Sils, Switzerland

“…Compared to the onshore realm, the number of scientific publications describing offshore tsunami deposits is limited (e.g., Dawson and Stewart 2008). Although the combined investigation of on-and offshore tsunami deposits may provide a more robust and accurate reconstruction of past events (Costa and Andrade 2020), only few case studies describe offshore tsunami deposits (e.g., Goodman-Tchernov et al 2009;Paris et al 2010;Smedile et al 2020;Tamura et al 2015). For example, Sakuna et al (2012) describe poorly sorted mud including terrigenous and anthropogenic components, which were transported from backwash currents of the 2004 Indian Ocean tsunami into the shallow marine environment of the Andaman Sea off the coast of Thailand.…”

Discovery of a tsunami deposit from the Bronze Age Santorini eruption at Malia (Crete): impact, chronology, extension

“…Origin of the coarse-grained deposits in core C21. Distinction between storm and tsunami deposits remains difficult and a subject of debate [28][29][30] . Nevertheless, the observations made at Malia offer solid arguments in favour of tsunami deposition.…”

Exploring Offshore Sediment Evidence of the 1755 CE Tsunami (Faro, Portugal): Implications for the Study of Outer Shelf Tsunami Deposits

“…Also, changes in the background sedimentation could be established and linked to paleoenvironmental changes. However, the small terrestrial fingerprint of the tsunami deposits calls for methodologies that reveal sedimentary structures, such as CT on X-ray core images, produced by wave motions and backwash flows of the tsunami [1,116]. Although it is possible to detect tsunami deposits in outer shelf environments, recent works suggest the inner shelf and more protected bays as a more suitable study area [5,15].…”

“…Research related to tsunamis has increased significantly in the last two decades, focusing not only on retrieving return periods, but also on understanding tsunami event dynamics [1]. Defining the coastal hazard of tsunamis by studying their sedimentary records benefits from their extensive chronology compared to instrumental or historic documentation [2][3][4].…”