Ground penetrating radar examination of thin tsunami beds — A case study from Phra Thong Island, Thailand

Gouramanis, Chris; Switzer, Adam D.; Polivka, P.; Bristow, Charles S.; Jankaew, Kruawun; Dat, Pham Tien; Pile, Jeremy; Rubin, Charles M.; Lee, Yingsin; Ildefonso, S.; Jol, Harry M.

doi:10.1016/j.sedgeo.2015.09.011

Cited by 29 publications

(24 citation statements)

References 57 publications

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“…1 m after palaeo-tsunami inundation4445. This was observed at locations where quartz OSL samples were collected between 0.4 and 0.6 m depth36.…”

Section: Discussionmentioning

confidence: 92%

“…Sandsheets B to D were likely formed during tsunami inundation following great earthquakes from the Sunda Trench subduction zone, of which Sandsheet A is a modern analogue21. However, the discovery of a sand sheet immediately between the Sandsheets A and B 30 (Sandsheet X) and additional sand sheets found between Sandsheet D and the base of Swale Y in Auger cores 8, 9 and 1044 (Fig. 3), imply a more complex overwash history than has thus far been presented.…”

Section: Discussionmentioning

confidence: 93%

“…Sandsheets B and D are also found in Swale Y but have a patchy distribution (Fig. 3)4445. Direct dating of the sand sheets using quartz OSL30323639, and bounding ages of the sandsheets using 14 C dating of bulk sediments29, plant and leaf fragments and buried shells21 have helped constrain the recurrence interval of sand sheet deposition on Phra Thong Island.…”

Section: Discussionmentioning

confidence: 99%

“…1), where high-frequency ground-penetrating radar44 identified a complex stratigraphy with more sand sheets than had been previously recognised from this swale. The new sand sheets may confound the consensus model presented above for palaeotsunami deposition on Phra Thong Island and have implications for Sunda Trench 2004 IOT-type tsunami recurrence213036.…”

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confidence: 91%

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High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

Gouramanis

Switzer

Jankaew

et al. 2017

Sci Rep

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The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.

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“…1 m after palaeo-tsunami inundation4445. This was observed at locations where quartz OSL samples were collected between 0.4 and 0.6 m depth36.…”

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 91%

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High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

Gouramanis

Switzer

Jankaew

et al. 2017

Sci Rep

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“…These events have renewed efforts to understand the impacts and frequency of past tsunamis on coastlines. New studies have improved our ability to identify their deposits in the sedimentary record (Gelfenbaum and Jaffe, 2003;Switzer et al, 2006;Morton et al, 2007;Gouramanis et al, 2015) and determine the inland extents and frequencies of past tsunamis across the globe (Kelsey et al, 2002;Schlichting and Peterson, 2006;MacInnes et al, 2016). However, despite these advances, identifying past tsunami deposits in areas marked by sandy shorelines without muddy or peaty backbarrier deposits remains difficult.…”

Section: Introductionmentioning

confidence: 99%

Coastal erosion and recovery from a Cascadia subduction zone earthquake and tsunami

et al. 2017

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Tsunamis generated by great earthquakes threaten coastal infrastructure, development, and human life. Earlier work has documented the inland extent and frequency of past tsunamis, but litle is known about the magnitude of material eroded during prehistoric tsunamis and how erosion and coastal recovery are recorded in coastal stratigraphy. In this study we use high-resolution ground-penetrating radar (GPR) to image and quantify coastal erosion experienced during a late Holocene (~900 cal BP) Cascadia subduction zone earthquake and tsunami along the northern California coast. The GPR profiles illustrate three stratigraphic signatures created during co-seismic subsidence and tsunami erosion and coastal recovery. The first is erosional truncation of the underlying seaward-dipping reflections created

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Could tsunami risk be underestimated using core‐based reconstructions? Lessons from ground penetrating radar

Takeda

Goto

Goff

et al. 2017

Earth Surf Processes Landf

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Where should we take cores for palaeotsunami research? It is generally considered that local depressions with low energy environments such as wetlands are one of the best places. However, it is also recognized that the presence or absence of palaeotsunami deposits (and their relative thickness) is highly dependent upon subsoil microtopography. In the beach ridge system of Ishinomaki Plain, Japan, several palaeotsunami deposits linked to past Japan Trench earthquakes have been reported. However, the number of palaeotsunami deposits reported at individual sites varies considerably. This study used ground penetrating radar (GPR) combined with geological evidence to better understand the relationship between palaeotopography and palaeotsunami deposit characteristics. The subsurface topography of the ~3000–4000 bp beach ridge was reconstructed using GPR data coupled with core surveys of the underlying sediments. We noted that the number (and thickness) of the palaeotsunami deposits inferred from the cores was controlled by the palaeotopography. Namely, a larger number of events and thicker palaeotsunami deposits were observed in depressions in the subsurface microtopography. We noted a total of three palaeotsunami deposits dated to between 1700 and 3000 cal bp, but they were only observed together in 11% of the core sites. This result is important for tsunami risk assessments that use the sedimentary evidence of past events because we may well be underestimating the number of tsunamis that have occurred. We suggest that GPR is an efficient and invaluable tool to help researchers identify the most appropriate places to carry out geological fieldwork in order to provide a more comprehensive understanding of past tsunami activity. Copyright © 2017 John Wiley & Sons, Ltd.

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Ground penetrating radar examination of thin tsunami beds — A case study from Phra Thong Island, Thailand

Cited by 29 publications

References 57 publications

High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

Coastal erosion and recovery from a Cascadia subduction zone earthquake and tsunami

Could tsunami risk be underestimated using core‐based reconstructions? Lessons from ground penetrating radar

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