Assessing the rate of post-depositional change within the 2004 Indian Ocean tsunami deposit: implications for long-term records of paleotsunamis

2021 ◽  
Author(s):  
Lillian Pearson ◽  
Jessica Pilarczyk ◽  
Andrea Hawkes ◽  
Chris Gouramanis ◽  
Jędrzej Majewski ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Relative Abundance ◽  
Soil Layer ◽  
Indian Ocean Tsunami ◽  
Time Interval ◽  
Tsunami Deposit ◽  
Foraminiferal Assemblage ◽  
Worst Case ◽  
2004 Indian Ocean Tsunami ◽  
Depositional Processes

<p>Foraminifera are commonly used to examine patterns of tsunami inundation occurring over centennial to millennial timescales. However, the impacts of post-depositional change on geologic reconstructions is unknown. In tropical environments, the taphonomic character (i.e. test surface condition) of a foraminifer can deteriorate, rendering them unidentifiable, and in the worst case, dissolve them entirely. Here, we investigate the rates and extent of post-depositional change associated with the foraminiferal assemblages found within the 2004 Indian Ocean Tsunami (IOT) deposit over a 15-year time interval in Aceh, Indonesia from 2007 to 2019. </p><p>The IOT deposit consisted of a 13-18cm thick, medium-fine sand unit that sharply overlays a muddy sand contact. During the 15-year time series analysis, the IOT deposit remained a consistent thickness and maintained easily recognizable stratigraphical contacts between the overlying soil layer and the underlying mud layer. The overlying soil layer increased in thickness from 2cm in 2007 to 6cm in 2019 and resulted in roots bioturbating the IOT deposit. Calcareous taxa dominated the IOT deposit assemblage, where hyaline taxa accounted for 62% of the assemblage, porcelaneous taxa for 34% of the assemblage and agglutinated taxa for 4% of the assemblage. The concentration of calcareous foraminifera within the tsunami deposit decreased by 5% from 2007 to 2019. This trend is attributable to the high abundance of delicate porcelaneous tests, which are more susceptible to post-depositional processes than the more robust hyaline tests. The taphonomic character of the foraminiferal assemblage became more corraded (dissolved, abraded and/or pitted) over the 15-year period. The relative abundance of corraded individuals within the foraminiferal assemblage increased by 4% in the IOT deposit, to reach a relative abundance of 50% by 2019 compared to 46% in 2007. Our results indicate that there is minimal change occurring within the deposit and presents good evidence that microfossils can be used as reliable indictors of tsunami origin and to identify characteristics of a tsunami deposit. While it is minimal, we recommend that post-depositional change should still be considered, especially with regards to the more delicate porcelaneous tests and over longer taphonomic timescales.</p>

scholarly journals Numerical Simulations of the 2004 Indian Ocean Tsunami Deposits Thicknesses and Emplacements

2018 ◽  
Author(s):  
◽  
Musa Al'ala ◽  
Hermann M. Fritz ◽  
Mirza Fahmi ◽  
Teuku Mudi Hafli
Keyword(s):  
Sediment Transport ◽  
Indian Ocean ◽  
Numerical Simulations ◽  
Field Data ◽  
Numerical Models ◽  
Indian Ocean Tsunami ◽  
Tsunami Deposit ◽  
Field Observations ◽  
Tsunami Deposits ◽  
2004 Indian Ocean Tsunami

Abstract. After more than a decade of recurring tsunamis, identification of tsunami deposits, a part of hazard characterization, still remains a challenging task not fully understood. The lack of sufficient monitoring equipment and rare tsunami frequency are among the primary obstacles that limit our fundamental understanding of sediment transport mechanisms during a tsunami. The use of numerical simulations to study tsunami-induced sediment transport was rare in Indonesia until the 2004 Indian Ocean tsunami. This study aims to couple two hydrodynamic numerical models in order to reproduce tsunami-induced sediment deposits, i.e., their locations and thicknesses. Numerical simulations were performed using the Cornell Multi-Grid Coupled Tsunami Model (COMCOT) and Delft3D. This study reconstructed tsunami wave propagation from its source using COMCOT, which was later combined with Delft3D to map the location of the tsunami deposits and calculate their thicknesses. Two Dimensional-Horizontal (2DH) models were used as part of both simulation packages. Lhoong, in the Aceh Besar District, located approximately 60 km southwest of Banda Aceh, was selected as the study area. Field data collected in 2015 and 2016 validated the forward modeling techniques adopted in this study. However, agreements between numerical simulations and field observations were more robust using data collected in 2005, i.e., just months after the tsunami (Jaffe et al., 2006). We conducted pit (trench) tests at select locations to obtain tsunami deposit thickness and grain size distributions. The resulting numerical simulations are useful when estimating the locations and the thicknesses of the tsunami deposits. The agreement between the field data and the numerical simulations is reasonable despite a trend that overestimates the field observations.

scholarly journals Numerical simulations of the 2004 Indian Ocean tsunami deposits' thicknesses and emplacements

2019 ◽  
Vol 19 (6) ◽  
pp. 1265-1280 ◽  
Author(s):  
◽  
Musa Al'ala ◽  
Hermann M. Fritz ◽  
Mirza Fahmi ◽  
Teuku Mudi Hafli
Keyword(s):  
Sediment Transport ◽  
Indian Ocean ◽  
Numerical Simulations ◽  
Field Data ◽  
Numerical Models ◽  
Indian Ocean Tsunami ◽  
Tsunami Deposit ◽  
Field Observations ◽  
Tsunami Deposits ◽  
2004 Indian Ocean Tsunami

Abstract. After more than a decade of recurring tsunamis, identification of tsunami deposits, a part of hazard characterization, still remains a challenging task that is not fully understood. The lack of sufficient monitoring equipment and rare tsunami frequency are among the primary obstacles that limit our fundamental understanding of sediment transport mechanisms during a tsunami. The use of numerical simulations to study tsunami-induced sediment transport was rare in Indonesia until the 2004 Indian Ocean tsunami. This study aims to couple two hydrodynamic numerical models in order to reproduce tsunami-induced sediment deposits, i.e., their locations and thicknesses. Numerical simulations were performed using the Cornell Multi-grid Coupled Tsunami (COMCOT) model and Delft3D. This study reconstructed tsunami wave propagation from its source using COMCOT, which was later combined with Delft3D to map the location of the tsunami deposits and calculate their thicknesses. Two-dimensional horizontal (2-DH) models were used as part of both simulation packages. Four sediment transport formulae were used in the simulations, namely van Rijn 1993, Engelund–Hansen 1967, Meyer-Peter–Mueller (MPM) 1948, and Soulsby 1997. Lhoong, in the Aceh Besar District, located approximately 60 km southwest of Banda Aceh, was selected as the study area. Field data collected in 2015 and 2016 validated the forward modeling techniques adopted in this study. However, agreements between numerical simulations and field observations were more robust using data collected in 2005, i.e., just months after the tsunami (Jaffe et al., 2006). We conducted pit (trench) tests at select locations to obtain tsunami deposit thickness and grain size distributions. The resulting numerical simulations are useful when estimating the locations and the thicknesses of the tsunami deposits. The agreement between the field data and the numerical simulations is reasonable despite a trend that overestimates the field observations.

Medieval forewarning of the 2004 Indian Ocean tsunami in Thailand

Nature ◽  
2008 ◽  
Vol 455 (7217) ◽  
pp. 1228-1231 ◽  
Author(s):  
Kruawun Jankaew ◽  
Brian F. Atwater ◽  
Yuki Sawai ◽  
Montri Choowong ◽  
Thasinee Charoentitirat ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Tsunami ◽  
2004 Indian Ocean Tsunami

A snapshot of the 2004 Indian Ocean tsunami: societal impacts and consequences

2006 ◽  
Vol 15 (1) ◽  
pp. 163-177 ◽  
Author(s):  
Havidan Rodriguez ◽  
Tricia Wachtendorf ◽  
James Kendra ◽  
Joseph Trainor
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Tsunami ◽  
2004 Indian Ocean Tsunami ◽  
Societal Impacts

scholarly journals Developing tsunami fragility curves based on the satellite remote sensing and the numerical modeling of the 2004 Indian Ocean tsunami in Thailand

2011 ◽  
Vol 11 (1) ◽  
pp. 173-189 ◽  
Author(s):  
A. Suppasri ◽  
S. Koshimura ◽  
F. Imamura
Keyword(s):  
Indian Ocean ◽  
Building Materials ◽  
Fragility Curves ◽  
Distribution Functions ◽  
Least Square ◽  
Indian Ocean Tsunami ◽  
2004 Indian Ocean Tsunami ◽  
Inundation Depth ◽  
High Resolution Satellite Images ◽  
Tsunami Fragility

Abstract. The 2004 Indian Ocean tsunami damaged and destroyed numerous buildings and houses in Thailand. Estimation of tsunami impact to buildings from this event and evaluation of the potential risks are important but still in progress. The tsunami fragility curve is a function used to estimate the structural fragility against tsunami hazards. This study was undertaken to develop fragility curves using visual inspection of high-resolution satellite images (IKONOS) taken before and after tsunami events to classify whether the buildings were destroyed or not based on the remaining roof. Then, a tsunami inundation model is created to reconstruct the tsunami features such as inundation depth, current velocity, and hydrodynamic force of the event. It is assumed that the fragility curves are expressed as normal or lognormal distribution functions and the estimation of the median and log-standard deviation is performed using least square fitting. From the results, the developed fragility curves for different types of building materials (mixed type, reinforced concrete and wood) show consistent performance in damage probability and when compared to the existing curves for other locations.

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