Modeling tsunami hazards from Manila trench to Taiwan

doi:10.1016/j.jseaes.2008.12.006

Journal of Asian Earth Sciences

Volume 36, Issue 1, 4 September 2009, Pages 21-28

https://doi.org/10.1016/j.jseaes.2008.12.006 Get rights and content

Abstract

The 2006 dual Pingtung earthquake event and the 2004 South Asia tsunami highlighted the potential tsunami hazards from Manila trench. Manila trench is only about 100 km away from Taiwan, therefore one shall punctuate the importance of thorough study on all possible tsunami scenarios for hazard mitigation. Based on the faults parameters issued by USGS and the seismic record from Global CMT, this study creates a hypothetical earthquake tsunami scenario caused by seismic motion at Manila trench. The magnitude of the earthquake is 9.35 (M_w), the total length is 990 km, and the maximum initial free-surface height is 9.3 m. The initial displacement profile is provided in this paper. An open source code, COMCOT, is adopted to perform the simulation of the tsunami propagation, runup, and inundation around Taiwan. Nested grid system and moving boundary technique are adopted to study runup and inundation.

The result shows that the maximum wave height is 11 m in southern Taiwan. Serious flooding is observed in the southwest coast of Taiwan. Tsunami inundation is able to reach 8.5 km inlandward. Due to the refraction effect, 8 m wave height is noted in the northeast coast of Taiwan. The detailed tsunami behavior around Taiwan is described in the context.

Introduction

The southwest (SW) Taiwan has been considered as a region of tectonic escape because of infrequent intense seismic activities (Lacombe et al., 2001). However, the SW Taiwan is not immune to the attacks of large earthquakes. One piece of the evidence is the Pingtung dual earthquakes on 26 December 2006. Two M_w = 7.0 offshore earthquakes with 8 min offset along with the 40 cm tsunami record highlighted the potential tsunami hazard on SW Taiwan coast.

Motivated by the Pingtung dual earthquakes, we wish to understand the potential devastating tsunami event and the hazard to Taiwan. The epicenters of 2006 dual Pingtung earthquakes is located at the north end of Manila (Luzon) trench, where the Eurasian plate is actively subducting eastward underneath the Luzon volcanic arc on the Philippine Sea plate. The east-dipping is initiated in the Miocene (22–25 Ma) and remains active to the present (Yumul et al., 2003, Queano et al., 2007). Recently, USGS has assessed Manila trench as a high risk zone to be a tsunami source. USGS Tsunami Sources Workshop 2006 (Kirby et al., 2006) further indentified six hypothetical fault planes based on the trench azimuth and the fault geometries (Table 1 and Fig. 1A).

To study the potential devastating hazard to SW Taiwan, the historical tsunami might be able to provide useful information. The 2004 Sumatra–Andaman earthquake with Indian Ocean tsunami is one notorious reference (Titove et al., 2005, Choi et al., 2005). With a similar length to the 1500 km Aceh-Andaman Megathrust, the subduction thrust under Manila trench which has accumulated strain over a 440-year period could become another Megathrust.

In this study, we refer to the three largest earthquakes in history, Global CMT seismic database, as well as the fault parameters issued by USGS, to create the worst-case scenario on the Manila trench and to study the hazard to SW Taiwan. A numerical approach is adopted to perform the simulation. The tsunami initial condition, maximum wave height, arrival time, wave period, and tsunami characteristics in Taiwan water area is addressed and discussed.

Section snippets

Fault parameters of Manila Megathrust

To characterize hypothetical fault planes along the Manila trench in the South China Sea (SCS), three largest historical tsunami earthquakes are referred. The earthquake parameters are shown in Table 2. All three earthquakes have similar length varying from 740 to 1300 km, similar width varying from 200 to 300 km, and similar earthquake magnitude ranging from M_w = 9.0 to 9.5. Using all of the information and referring to the fault geometry, a set of hypothetical fault of Manila Megathrust is nailed

Tsunami propagation model

The numerical approach is applied to this study. The well validated open source code, COMCOT (Cornell Multi-grid Coupled Tsunami Model), is chosen to perform the simulation. The COMCOT model has been used to investigate tsunami events, such as the 1992 Flores Islands (Indonesia) tsunami (Liu et al., 1994, Liu et al., 1995), the 2003 Algeria tsunami (Wang and Liu, 2005), and more recently the 2004 Indian Ocean tsunami (Wang and Liu, 2006). The COMCOT model is capable of solving both linear and

Bathymetry and grid setup

To simulate both far-field and near-field tsunami propagation, four grid layers are adopted and referred as Grids 1, 2, 3A, and 3B (Fig. 3). The grid information as well as the governing equations are shown on Table 5. Finer grid layers, Grids 3A and 3B, are placed in the SW Taiwan to study the tsunami inundation and runup in depth.

Results and discussion

To study the characteristics of the tsunamis in Taiwan, several virtual wave gauges are installed. Fig. 4 shows the virtual gauge location and the time-history free-surface elevation. Time zero denotes the instant when rupture occurs. The gauge record shows that it takes only 20 min for the first tsunami wave to arrive Kenting, a famous tour spot in Taiwan. The wave period is about 25 min at wg_3A_2 and wg_3A_3, and about 20 min at wg_3A_1. The waves merge when they propagate from the deep-water

Conclusion

From the hazard mitigation point of view, we shall clearly understand the potential devastating tsunami hazards. In this study, we create a worst-case scenario of tsunami earthquake excited by Manila Megathrust. The fault parameters are referred to the data issued by USGS, historical tsunamis, and Global CMT. The earthquake magnitude, M_w, is assumed to be 9.35. The total length of the Manila Megathrust is 990 km.

The initial tsunami profile is provided. The maximum initial wave height is 9.3 m (

Acknowledgements

The authors are grateful to Professor Philip L.-F. Liu of Cornell University for providing the latest version of COMCOT and Dr. Xiaoming Wang of Cornell University for providing technical support on using COMCOT.

This work is founded by the National Science Council, Taiwan. Project No: 95-2116-M-008-006-MY3.

References (12)

O. Lacombe et al.
Structural geodetic and seismological evidence for tectonic escape in SW Taiwan
Tectonophysics
(2001)
B.H. Choi et al.
Post runup survey of the December 26, 2004 earthquake tsunami of the Indian Ocean
Kirby, S., Geist, E., Lee, W.H.K., Scholl, D., Blakely, R., 2006. Tsunami source characterization for Western Pacific...
P.L.-F. Liu et al.
Runup of solitary waves on a circular Island
Journal of Fluid Mechanics
(1995)
Liu, P.L.-F., Cho, Y.-S., Yoon, S.-B., Seo, S.-N., 1994. Numerical simulations of the 1960 Chilean tsunami propagation...
L. Manshinha et al.
The displacement fields of inclined faults
Bulletin of the Seismological Society of America
(1971)

There are more references available in the full text version of this article.

Cited by (68)

Forward numerical investigation of potential tsunami deposits in the South China sea: A case study of Nan'ao Island
2024, Marine and Petroleum Geology
The South China Sea (SCS) coastlines are particularly vulnerable to tsunamis due to rapid urbanization and dense infrastructures. However, whether the SCS has experienced ocean-wide tsunamis is still under debate. Some geological records from the offshore islands inside the SCS imply a regional tsunami event may have occurred approximately 1000-yr-ago. We address these questions for the first time using forward numerical simulations in the SCS: what source could be responsible for such deposits, how the deposits were formed and at what conditions do the deposits could be preserved? Here, we assume the validity of the tsunami deposit hypothesis and use the forward model COMCOT-SED to investigate if these tsunami deposits can be linked to potential seismogenic tsunami sources inside the SCS, including megathrust earthquakes (Mw8.8–9.2) from the Manila subduction zone (MSZ) and the 1918 Mw7.5 Nan'ao earthquake from the Littoral Fault Zone (LFZ) in the northern continental shelf of the SCS. We also utilize a reported tsunami deposit from Qing'ao Embayment, Nan'ao Island, China, to exemplify the deposit formation process in a typical barrier-low coastal plain system. Quantitative analysis suggests large earthquakes from the MSZ may account for the reported geological deposits. The full-rupture earthquake scenario could best explain the depositions if such extreme case is geophysically and geologically plausible. If not, earthquakes (∼ Mw 9.0) covering the northern (16–23.5°N) or southern portion (14–19°N) of the MSZ could also be suitable candidates. Such great earthquakes can generate large tsunami waves (>7 m) that inundate the Qing'ao Embayment, transporting sediments and leaving tsunami deposits in low-lying areas. Conversely, tsunamis triggered by nearshore earthquakes in the LFZ cannot cause deposition in Qing'ao Embayment. The barrier-low coastal plain system is well-suited for preserving tsunami deposits, which remain unaltered by subsequent tsunami waves. Our findings offer a quantitative reference for paleo-tsunami research in the SCS and enhance global understanding of the tsunami deposition process in barrier-low coastal plain systems.
Optimal deployment of seafloor observation network for tsunami data assimilation in the South China Sea
2022, Ocean Engineering
We propose an optimal deployment scheme of the Seafloor Observation Network (SON) in the South China Sea (SCS), aiming at early warning of potential tsunami hazards based on the data assimilation approach. The SON is composed of offshore bottom pressure gauges (OBPGs). We design the initial location of OBPGs along the isobaths of 500, 1000, and 2000 m. The energy distribution of the tsunami wavefield based on Empirical Orthogonal Function (EOF) analysis is used as a reference. Then, synthetic tsunamis generated by stochastic slip sources along the Manila Trench are adopted to evaluate the performance of the SON. The OBPGs at a depth of 1000 m can make an accurate early warning based on tsunami data assimilation at a reasonable engineering cost. Finally, based on the quantitative evaluation, the optimal deployment scheme of the SON is suggested. Our results indicate that at least three stations are required to cover the coast along southern China to forecast the tsunami in the SCS successfully. We note that our method could also be applied to other regions to design the SON against potential tsunami hazards.
Effect of tsunami load induced by earthquake at Manila Trench on transmission tower
2021, Ain Shams Engineering Journal
The Manila Trench subduction zone is an active convergent plate margin between the South China Sea and northern Philippines. This strongly indicates a high probability for larger earthquakes that could potentially trigger a tsunami in the future and anticipated to affect neighboring countries such as Malaysia which has power plants near the coastal areas. The potential disastrous impact of tsunami waves on a power plant causes loss of lives, damage to assets, and loss of electricity for the coastal communities similar to year 2011 Tohoku tsunami in Japan. Therefore, application of shallow water equation (SWE) in tsunami modelling namely generation and propagation phase and nonlinear shallow water equation (NSWE) for run-up and inundation phase of a tsunami event are pertinent in simulating various scenarios of tsunami. Results from tsunami simulation is used as tsunami lateral load. Linear Static Analysis is then utilized to analyze stability of 275-kV transmission tower.
Impacts of extreme events on hydrodynamic characteristics of a submerged floating tunnel
2020, Ocean Engineering
A submerged floating tunnel (SFT) is a promising alternative to conventional bridges and tunnels, and can be potentially built in the Qiongzhou Strait in China. However, this area is under the threat of disasters including mega tsunamis and severe storm surges. To evaluate the hydrodynamic loads of the SFT in this hazardous zone subject to severe tsunami and typhoon impacts, the Delft3D-FLOW hydrodynamic model and SWAN wave model are coupled, and a Computational Fluid Dynamics (CFD) method is adopted. The maximum probable tsunami and typhoon Rammasun (July 2014) are selected as hazard assessment conditions in the Qiongzhou Strait. Whether the tsunami and hindcast storm surge cause extreme forcing and bring challenges to the SFT engineering design, operation, and maintenance in the Qiongzhou Strait are discussed in this study. We reveal that the typhoon impacts are more devastating than tsunami for an SFT in the Qiongzhou Strait. In order to determine the optimal SFT cross-section under extreme events, we use a parametric Bezier curve profile compared with two simpler shapes including circular and elliptical cross sections. In-line force and lift are respectively applied to evaluate the SFT's hydrodynamic behaviour. Our results reveal that the gross horizontal force on the parametric Bezier curve shape is more sensitive to flow acceleration, while the circular cross-section is dominated by current speed. The parametric Bezier curve cross-section shape has the preferable property of reducing the in-line force and postponing serious vortex shedding compared with the two simpler shapes.
Tsunami deposits and recurrence on a typhoon-prone coast of northern Taiwan from the last millennium
2020, Quaternary Science Reviews
Widely known for its hazardous history, Taiwan holds valuable records of NW Pacific tsunamis and typhoons. Despite the similarity between tsunami and typhoon deposits, historical accounts enabled the identification of the 1867 tsunami deposit on the northern coast through matching with the record-setting inundation. However, the identification of prehistoric tsunami deposits has been hindered by severe sediment reworking and post-depositional changes produced by the typhoon-prone, tropical, and humid climate. In this study, we investigated the upper Holocene facies and their sediment sources and radiocarbon ages on distal floodplains and rocky backshores of the northern coast, where sediment reworking is less intense. Four decimetre-thick gravelly layers were identified, intercalated with fluvial mud and colluvium. The gravelly layers are composed of beach-derived quartz-rich sand and rounded gravels of the sedimentary basement rocks, longshore-drift andesite and stranded pumice. The remarkable layer thickness, gravel size, and quartz richness were determined to have endured post-depositional changes. The event layers are sharp-based, matrix-supported, and poorly sorted and have recorded scouring, sediment entrainment and rapid fallout of suspension-rich turbulent flows that probably originated with tsunamis. The event layers occur 0.5–0.8 km inland and 3–11.5 m above sea level, matching the 1867 tsunami inundation and wave height, respectively. Radiocarbon dating tied the event layers to the 1867 tsunami and three prehistoric events that occurred in the periods: 1545 to 1810, 1293 to 1414 and 1090 to 1235, representing a recurrence interval of 83–436 years over the last millennium.
Field observations of sediment transport across the rocky coast of east Taiwan: Impacts of extreme waves on the coastal morphology by Typhoon Soudelor
2020, Marine Geology
Citation Excerpt :
After the catastrophic 2011 Tohoku earthquake in Japan, the threat of tsunami has greatly drawn public's attention, especially for the countries situated around the Pacific Ring of Fire. In Taiwan, researches have suggested the possible scenarios of paleo-tsunamis (Lallemand et al., 2016; Liu et al., 2007; Nobuhisa et al., 2013; Wu and Huang, 2009). The records of the tsunamis were reported mostly in the north tip of the island (Yu et al., 2016), the southwest part of Taiwan (Lau et al., 2010; Lu et al., 2019), and also the regime of the east coast (Lau et al., 2010).
After the 2015 Typhoon Soudelor, large boulders and mixed sediments deposited extensively across the beach along the east coast of Taiwan. Field measurements of these storm-related sediments provide the first-hand evidence to document the impacts of extreme waves induced by Typhoon Soudelor. Although the maximum inundation distance is only 170 m due to the lack of beach buffer zone, the weight of the largest boulder was estimated over 1 t and the maximum run-up was estimated up to 11.9 m. The clast distribution of the washover and the beach face sediments exhibited reverse directions of coarsening, reflecting different stages of wave propagation. Our field records show that a super typhoon like Soudelor can potentially leave footprints of extreme values in the geologic records. Therefore, a comprehensive understanding on the occurrence of the sediments and the depositional environment should be carefully considered to pin down the origin of the archived extreme events. In addition, the formation of the higher extreme wave berm and the destruction of the lower swell berm at the Yen-liao Beach displayed the power of the storm surges, suggesting the important role of the run-up on the evolution of the berm.

View all citing articles on Scopus

View full text

Modeling tsunami hazards from Manila trench to Taiwan

Abstract

Introduction

Section snippets

Fault parameters of Manila Megathrust

Tsunami propagation model

Bathymetry and grid setup

Results and discussion

Conclusion

Acknowledgements

Tectonophysics

Post runup survey of the December 26, 2004 earthquake tsunami of the Indian Ocean

Runup of solitary waves on a circular Island

Journal of Fluid Mechanics

The displacement fields of inclined faults

Bulletin of the Seismological Society of America