Sustainable Development Goals

Abstract/Objectives

Taiwan’s eastern coast and offshore islands are facing severe tsunami risks, according to the historical accounts and the first reports of tsunami boulders in the country. However, at least three uncertainties remain to be clarified. The historical accounts tend to be vague and thus fraught with ambiguities. The previous hydrodynamic study related the reported event boulders to typhoons, rather than tsunamis. The geological and historical events are associated with the prolonged intervals of thousands of years in length, and provide limited clues to the future events. In order to scrutinize the tsunami history of this region, this study plans to investigate the upper Holocene facies and establish the millennium-scale event stratigraphy of southern Taiwan. The stratigraphic scheme will integrate and take advantage of the results of our previous MOST project in Penghu, Chiayi, and Tainan to promote the efficiency and applicability of the study. The results of this study are anticipated to demonstrate the tsunami recurrence intervals.

Results/Contributions

The characteristics and distributions of the tsunami facies, geochemistry, and geophysics record the processes of erosion, transportation, deposition during the tsunami inundations. Accordingly, the marine invasion, run-up, wave height, and coastal changes in geomorphology and ecology are to be reconstructed. In addition, this study also plans to apply forward and backward numerical simulations to assess the validities of the inferred tsunamis. The best-fit, worse case scenarios of the tsunamis are to demonstrate the probable impacted coast and related damages, on which the future mitigation may be based.

This study plans to spend the three years from 2024 to 2026 on investigating the outcrops and subsurface geology in the coastal area from Taitung to Hualien and Yilan and on the offshore islands of Lutao and Lanyu. The forward and backward stimulations are also included and planned to integrate the results of this study and also those of the Penghu-Chiayi-Tainan area. The ultimate goal is aimed at demonstrating the history, magnitudes, sources, and recurrence intervals of the regional tsunamis. At present, the present is the first 2024—2025 project year with the investigation focused on the Taitung area.

Keywords

Taiwan’s southern coast, offshore islands, tsunami deposit, facies, event stratigraphy, Upper Holocene, numerical simulation

References

1. https://www.sciencedirect.com/science/article/pii/S0277379122000543

1. Yu, N.-T., Yen, J.-Y., Yen, I. C., and Chu, M.-F., 2022, An extended, 2.4-ka long record of western Pacific tsunamis and pumice rafts in northern Taiwan: Tsunami recurrence, pumice sources, and drifting routes: Quaternary Science Reviews, v. 281, p. 107423.

2. https://www.sciencedirect.com/science/article/pii/S0277379120304509

2. Yu, N.-T., Yen, J.-Y., Yen, I. C., Hirakawa, K., and Chuang, C.-M., 2020, Tsunami deposits and recurrence on a typhoon-prone coast of northern Taiwan from the last millennium: Quaternary Science Reviews, v. 245, p. 106488.

3. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JF004831

3. Sugawara, D., Yu, N. T., and Yen, J. Y., 2019, Estimating a Tsunami Source by Sediment Transport Modeling: A Primary Attempt on a Historical/1867 Normal-Faulting Tsunami in Northern Taiwan: Journal of Geophysical Research: Earth Surface, v. 124, no. 7, p. 1675-1700.

4. https://www.sciencedirect.com/science/article/pii/S1367912019301191

4. Lu, C.-H., Yen, J.-Y., Chyi, S.-J., Yu, N.-T., and Chen, J.-H., 2019, Geological records of South China Sea tsunamis on Penghu Islands, Taiwan: Journal of Asian Earth Sciences, v. 177, p. 263-274.

5. https://www.sciencedirect.com/science/article/abs/pii/S0025322715300694

5. Yu, N.-T., Yen, J.-Y., Chen, W.-S., Yen, I. C., and Liu, J.-H., 2016, Geological records of western Pacific tsunamis in northern Taiwan: AD 1867 and earlier event deposits: Marine Geology, v. 372, p. 1-16.

Contact Information

游能悌 Neng-Ti Yu
ntyu@mx.nthu.edu.tw