Chemical and environmental impact related to geohazards in subduction zones
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Date
2012-08-05
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Australian Geosciences Council
Abstract
Major tsunamis generated in subduction zones are nothing new. However, it is only recently that the chemical and environmental impact of these devastating events on land has been investigated. Chemical data gathered during post-tsunami surveys following the 2009 South Pacific (Samoa), 2010 Maule (Chile) and 2011 Tohoku-oki (Japan) tsunamis are presented and compared. These studies show that tsunami inundation has resulted in saltwater contamination of soils, sediments and surface waters. While rainfall has led to some dilution over time, the marine chemical signature was still recorded six months after the events, both in the sediments/soils and water bodies. This reflects a long-term impact of tsunami inundation, particularly in farmland areas, where the re-establishment of farming (e.g. rice) was hindered due to saltwater contamination. Fine sediments (mud) and soils retained the marine signature, but this was less evident in sandy deposits. Of particular note however,
geochemical markers were found beyond the recognisable limit of sand deposition, even six months after the tsunamis, indicating that in absence of reliable sedimentological evidence they can be used to identify the true limit of tsunami inundation. This study highlights not only the long-term environmental impact of tsunami inundation, but also the usefulness of geochemical markers to identify palaeotsunami deposits and the extent of tsunami inundation beyond the limit of sand deposition. The latter findings have important implications for modelling, and tsunami risk assessment and mitigation.
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Keywords
Environmental effects, Hazards, Tsunamis, Japan, Data, Pacific Ocean, Sediments, Soils, Risk assessment
Citation
Chague-Goff, C. (2012). Chemical and environmental impact related to geohazards in subduction zones. Paper presented to the 34th International Geological Congress 2012, "Unearthing our Past and Future - Resourcing Tomorrow", Brisbane, Australia, 5-10 August 2012. (pp. 1937).