Tsunami hazard and early warning system in South China Sea

doi:10.1016/j.jseaes.2008.12.010

Journal of Asian Earth Sciences

Volume 36, Issue 1, 4 September 2009, Pages 2-12

https://doi.org/10.1016/j.jseaes.2008.12.010 Get rights and content

Abstract

In this paper, we discuss the potential tsunami hazard in the South China Sea region. We focus our discussions on the characteristics of tsunamis generated from earthquakes along the Manila subduction zone. A procedure is presented for establishing a tsunami early warning system in the region. A scenario case is used to demonstrate the feasibility of the early warning system.

Introduction

Tsunami is one of the most devastating natural coastal disasters. Most of large tsunamis are generated by submarine earthquakes occurring in subduction zones. Tsunamis can also be triggered by volcano eruptions and large landslides. Although the skill for predicting earthquake is still in its infancy, a tsunami warning system is still possible for a distant tsunami if the tsunami can be detected in the open-ocean. Information on the arrival time and the height of leading tsunami wave in areas far away from the source region can be predicted with some confidence (e.g., Wei et al., 2003).

Such a tsunami warning system is now operational in the Pacific Ocean and has proven its effectiveness and validity for several recent tsunami events. If a similar early warning system had been available in the Indian Ocean, the 2004 Indian Ocean tsunami would have caused much less damage in property and loss in human lives in Sri Lanka, India, Maldives and other coastal regions.

In the South China Sea (SCS) region, the Manila subduction zone has been identified as a high hazardous tsunamigenic earthquake source region. No earthquake larger than M_w = 7.6 has been recorded in the past 100 years in this region, suggesting a high probability for larger earthquakes in the future. And most alarmingly, there is no operational tsunami warning system in place in this region. If a tsunamigenic earthquake were to occur in this region in the near future, a tragedy with the magnitude similar to the 2004 Indian Ocean tsunami could repeat itself.

In this paper, potential tsunami hazard in SCS region is studied and a procedure for establishing a tsunami early warning system is presented (Satake, 1987, Titov et al., 2001). This system will be capable of releasing early warning information, including both tsunami arrival times and wave heights, to the surrounding countries for earthquakes along the Manila subduction zone. Using this information as input, inundation forecasts will also be possible by applying tsunami runup models in coastal regions of interest.

Section snippets

Hazardous tsunamigenic zones in South China Sea

In the 2006 USGS tsunami source workshop (Kirby et al., 2006), three subduction zones, the Manila subduction zone, Ryukyu subduction zone and N. Sulawesi subduction zone, were identified as having high potentials to generate hazardous tsunamis (Fig. 1).

Preliminary numerical studies have indicated that tsunamis generated from the Ryukyu subduction zone and N. Sulawesi subduction zone will not directly affect countries surrounding the South China Sea. Tsunamis generated from the Ryukyu subduction

Simulation of tsunamis generated along Manila Trench

In this section, we analyze the tsunami arrival time and amplitude distribution using the hypothetical earthquake of magnitude M_w = 8.0 with the fault plane parameters as listed in Table 3. The simulated results will help to identify the correlation between most affected coastal areas with the fractured fault plane segment. The arrival time analysis will also provide important information in selecting the locations of tsunami deep-ocean sensors.

In simulating tsunami propagations, we first assume

General procedures

The establishment of a tsunami early warning and forecasting system involves the following stages:

•
Deployment of tsunami sensors.

The locations of tsunami sensors in deep-ocean need to be determined based on the understanding on source region characteristics, tsunami arrival times and the coastal areas to be protected.

•
Construction of unit sources.

The entire subduction zone needs to be divided into small segments; each segment is treated as “unit” source for tsunami generation.

•
Pre-tsunami

Concluding remarks

In this paper, we have demonstrated that potential for a strong future earthquake along the Manila subduction zone is real. Using a numerical model, we have also shown that most of surrounding countries in the South China Sea will be affected by the tsunamis generated by the future earthquake. The simulated results show that the leading tsunami waves will reach most of coastal communities in China, Vietnam, Malaysia, and Taiwan within 1–2 h. We have proposed a procedure to establish a tsunami

Acknowledgement

The research presented in this paper has been supported by National Science Foundation through grants to Cornell University.

References (11)

C.-H. Lin
Thermal modeling of continental subduction and exhumation constrained by heat flow and seismicity in Taiwan
Tectonophysics
(2000)
Kirby, S. et al., 2006. In: USGS Tsunami Sources Workshop (2006): Great Earthquake Tsunami Sources: Empiricism and...
Lee, W., 2006. Personal...
P.L.-F. Liu et al.
Numerical simulations of the 1960 Chilean tsunami propagation and inundation at Hilo, Hawaii
P.L.-F. Liu et al.
Run-up of solitary waves on a circular island
J. Fluid Mech.
(1995)

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

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Tsunami hazard and early warning system in South China Sea

Abstract

Introduction

Section snippets

Hazardous tsunamigenic zones in South China Sea

Simulation of tsunamis generated along Manila Trench

General procedures

Concluding remarks

Acknowledgement

Tectonophysics

Numerical simulations of the 1960 Chilean tsunami propagation and inundation at Hilo, Hawaii

Run-up of solitary waves on a circular island

J. Fluid Mech.