Geochemical approaches in tsunami research: current knowledge and challenges

Abstract

Over the past decade or so, geochemical techniques have been applied to the study of modern and past tsunamis. Seawater incursions and the introduction of marine organic matter can be detected through geochemical analysis, providing strong evidence that an event deposit was formed by saltwater inundation. Furthermore, the marine geochemical signature of an event may reveal the full extent of tsunami inundation far more precisely than can be obtained from sediment alone. Based mainly on literature published during the last 4 years, this paper summarizes the latest advances in and some problems with tsunami geochemical research, and specifically addresses organic and inorganic proxies with high preservation potential, geochemical characteristics of invisible tsunami deposits, handling of data from core scanners, and offshore environmental impacts. Recent studies have proposed that some organic and inorganic geochemical proxies have high preservation potential, and sometimes such evidence can be recognized from invisible tsunami deposits. Quantitative assessments of biomarkers are also effective for detecting allochthonous materials. Organic and inorganic proxies can be applied both to identify tsunami deposits and to accurately reconstruct tsunami inundation areas; however, there are as yet no universal criteria for accurate reconstruction of tsunami inundation areas by detecting invisible tsunami deposits using geochemical approaches. For deeper understanding of the behavior of geochemical characteristics derived from tsunami events, additional knowledge of the geochemical substances associated with modern and paleo-tsunami events is required. Specifically, further work is required on assessment of the environmental selectivity of geochemical proxies and refinement of core-scanner analysis for both organic and inorganic substances.

Giant mid-Holocene landslide-generated tsunamis recorded in lake sediments from Saqqaq, West Greenland

“…The MS has a step size of 4 mm, and the optical scan has a resolution of 0.047 mm. The ITRAX core scanner provides counts of c. 40 elements, and it has been used to identify tsunami deposits onshore and in lake cores (e.g., Chagué-Goff et al, 2017;Shinozaki, 2021). In this study, we use the element Titanium (Ti) as a proxy for minerogenic input to the lake (e.g., tsunami and glaciofluvial deposits) and the element ratio Ca/Fe as a proxy for marine influence in the sediment i.e., in tsunami deposits.…”

Identifying tsunami traces beyond sandy tsunami deposits using terrigenous biomarkers: a case study of the 2011 Tohoku-oki tsunami in a coastal pine forest, northern Japan

“…Biomarkers were measured in samples A1, A4, A6, A7, and the reference sample, as well as in the pine materials taken from the ground surface. Because large plant fragments constitute a large portion of the organic matter present in these sediments (Shinozaki 2021), terrestrial plants were mostly removed from each subsample using a 250-µm sieve, and fraction ner than 250-µm in each subsample was then dried and homogenized. Lipids were extracted from the homogenized subsamples with dichloromethane and methanol using an accelerated solvent extractor (ASE350, Dionex, Sunnyvale, USA).…”

Non-seismic and Complex Source Tsunami: Unseen Hazard

“…Despite Japan's advanced tsunami warning system and strict building codes, the magnitude of the event far exceeded expectations, leading to widespread devastation. It underscored the fact that, while we have made significant advancements in our understanding of tsunamis and their seismic triggers, there is still much work to be done [26]. In conclusion, while undersea earthquakes are the primary trigger of tsunamis, the conditions leading to their generation are multifaceted, involving the interplay of earthquake magnitude, depth, and type of seismic activity.…”