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

Abstract

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.

Response to Referee #3 on Review of “Numerical Simulations of the 2004 Indian Ocean Tsunami Deposits Thicknesses and Emplacements"

“…In the original form of our manuscript we presented the result based on van Rijn 1984 Sediment Transport formulae. Detailed documentation of the sediment transport formulae can be seen in Delft Hydraulics (2009). We also highlight the limitation of our study in the discussion section (Section 5) and in the Conclusion (Section 6) in our revised manuscript.…”

Responses to Detailed Comments from Referee #3

“…RESPONSE 3: The version of DELFT3D that we operate does not allow us to put the offshore multi-fault scenario that could reconstruct the 2004 Indian Ocean tsunami case. The multi-fault scenario for the 2004 Indian Ocean tsunami is more valid than the single fault (Piatanesi and Lorito, 2007;Koshimura et al, 2009 ;Syamsidik et al, 2015;Romano, 2009). All these study have validate the tsunami waves generated using tsunami poles (inland), measured water marks on buildings, and water level measured offshore by Satellite Jason 1.…”

Performance Evaluation of DualSPHysics and COMCOT Programs through Numerical Testing for Simulating Tsunami Propagation and Overtopping on Seawalls

“…For instance, one research study focused on reconstructing the Mentawai tsunami event, aiming to validate tsunami run-up height by comparing the findings of field studies conducted by the GITST Team in 2010 [16]. Additionally, another numerical investigation, pertaining to the 2004 Indian Ocean Tsunami conducted by [17], centered on researching land separation due to hydrodynamic forces and the resulting overtopping phenomenon in the Ujong Seudeun area, induced by the tsunami.…”