Geological records of South China Sea tsunamis on Penghu Islands, Taiwan

Lu, Cheng-Hao; Yen, Jiun-Yee; Chyi, Shyh-Jeng; Yu, Neng-Ti; Chen, Jiahong

doi:10.1016/j.jseaes.2019.02.027

Cited by 12 publications

(23 citation statements)

References 23 publications

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“…A previously reported Suogang/SG outcrop was included for comparison (blue circle 4 in Fig. 1B; Lu et al, 2019). All studied outcrops are in the supratidal zone with top surfaces at an elevation of 2.5-5.3 m a.s.l.…”

Section: Coastal Outcrops and Facies-stratigraphic Analysismentioning

confidence: 99%

“…Accounts of the late 18th century tsunami in SW Taiwan remain controversial in terms of several aspects including age (1781 or 1782), death toll (one or tens of thousand), the extent of inundation (tens of meters or tens of kilometers), and whether the event was coupled with an earthquake (Li et al, 2015;Lau et al, 2010;Liu et al, 2022). Recent geological investigations have identified three event layers from the 4th to the 16th centuries across the South China Sea (Lu et al, 2019;Sun et al, 2013;Ramos et al, 2017;Yang et al, 2019). However, further information is required for an accurate quantitative evaluation of the landward inundation, wave heights, and run-ups.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, the Penghu Islands in the Taiwan Strait in the NE South China Sea were selected for further geological investigation because of their close proximity to several tsunami sources and the previous discovery of three paleotsunami deposits in the area (Fig. 1A; Lu et al, 2019), with a new and younger marine gravel deposit from the 17th century identified at several coastal localities. The cliff-top basalt boulders at one of the coastal exposure sites provide crucial clues for estimating wave heights and periods during sediment transport and deposition, and have been considered in this study for the first time.…”

Section: Introductionmentioning

confidence: 99%

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Boulder transport and wave height of a seventeenth century South China Sea tsunami on Penghu Islands, Taiwan

Yen

et al. 2023

Preprint

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Abstract. The widespread tsunami risks in the South China Sea have diverse origins from trench megathrust to intraplate earthquake or landslide and remain poorly understood due to the scarce historical and geological records. The cliff-top paleotsunami gravels and basalt boulders on Penghu Islands in the Taiwan Strait present facies constraints on sediment transport, wave estimates from incipient motion formulas, and stratigraphic links to the probable sources. The boulders are supported by a pumice-bearing mud matrix that reflects a suspension-rich turbulent flow process and the typical rolling–saltation transport that results from bore-like waves. Calibrating for ancient sea level height and 100 year surge indicates that the storm waves that are likely to form in the shallow interisland bathymetry only enable boulder sliding–rolling and are incapable of the 2.5 m high cliff-top deposition. The estimated minimum height of tsunami waves is also insufficient and needs to add to 3.0 m high for a minimum cliff-top overflow of 0.5 m depth for terminal rolling before deposition. Coeval gravels in two other outcrops also record the time and extent of tsunami deposition, and are characterized by beach-derived bioclasts and stranded pumices, sharp base, matrix support, poor sorting, and elevation reaching above the 100 year surge. The gravels mark the local minimum wave run-ups and reach 2.4–4.0 m above sea level. The 1575–1706 radiocarbon age of the studied boulder suggests a probable tie to the disastrous 1661 earthquake in the SW Taiwan Orogen and the megathrust source in the northern Manila Trench.

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Section: Coastal Outcrops and Facies-stratigraphic Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Boulder transport and wave height of a seventeenth century South China Sea tsunami on Penghu Islands, Taiwan

Yen

et al. 2023

Preprint

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“…A recent study by Lu et al. (2019) has revealed geological records of three possible tsunami events since 400 AD on the islands with a recurrence interval of 400–500 years, highlighting the importance of evaluating the tsunami risks of the region. We present the first case study of tsunami hazard assessment using photogrammetric bathymetry, showing the improvement in hazard assessment.…”

Section: Introductionmentioning

confidence: 99%

“…We select the Penghu Islands (Figure 1), located in the northeastern corner of the South China Sea, as a test area because it is densely populated and threatened by tsunamigenic earthquakes that may occur along the Manila subduction zone. A recent study by Lu et al (2019) has revealed geological records of three possible tsunami events since 400 AD on the islands with a recurrence interval of 400-500 years, highlighting the importance of evaluating the tsunami risks of the region. We present the first case study of tsunami hazard assessment using photogrammetric bathymetry, showing the improvement in hazard assessment.…”

Section: Introductionmentioning

confidence: 99%

A Generic Method to Derive Coastal Bathymetry From Satellite Photogrammetry for Tsunami Hazard Assessment

Zhou

et al. 2021

Geophysical Research Letters

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Tsunami hazard assessment relies heavily on coastal bathymetry (underwater topography) as it ultimately determines tsunami-wave propagation and inundation. However, high-resolution and high-accuracy coastal bathymetric data are scarce worldwide because they are rather difficult and expensive to obtain from traditional methods such as light detection and ranging (LiDAR). Here, we use 0.5-m resolution Pleiades satellite stereo imagery as an alternative to map shallow-water bathymetry specifically for the purpose of assessing tsunami hazard in coastal regions. A key step in this method is refraction correction (when the ray of light passes the water/air interface, it bends), in which the refractive index of the media is vital. We measure for the first time the refractive indices of seawater mixed with a variety of phytoplankton. We find that although the refractive indices of seawater change with heterogeneous distribution of phytoplankton, errors arising from such changes are negligible. This demonstrates that the method is generic and can be applied to the global ocean, without any requirements for in situ data. Using the newly derived photogrammetric bathymetry, we simulate a tsunami scenario to show the improvement in our ability of assessing tsunami hazard.

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Groundwater potential mapping based on long time series remote sensing data in Penghu Islands, China

Cheng

Cui

Wang

et al. 2022

Geoscience Data Journal

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Islands are special bodies of land surrounded by seawater. Many islands are facing water shortages as the demand for groundwater increases, thus, highlighting the importance and urgency of the assessment, planning, and management of island groundwater resources. To facilitate the same, the groundwater potential of the Penghu Islands in China was assessed for the first time using remote sensing (RS), geographic information system (GIS), and the analytic hierarchy process (AHP). Long‐term series remote sensing studies were also conducted to monitor the dynamic change in groundwater potential and to identify groundwater potential areas. In this study, the geological environment factors were normalized, and their weight was allocated based on the AHP of RS and GIS. The groundwater potential assessment (GPA) index, established using the weighted comprehensive algorithm, was used to analyse groundwater potential and demarcate groundwater potential zones. Finally, the trend in the spatio‐temporal variation of groundwater potential was analysed using long‐term series remote sensing data. The results from 2015 to 2021 showed that the Penghu Islands can be divided into five groundwater potential zones of different grades, such as 6.3%–8.1% of grade I, 22.2%–24.2% of grade II, 23%–24.4% of grade III, 19.6%–21% of grade IV, and 25.1%–25.5% of grade V. The results of the GPA were verified by comparing them with the abundance of water‐content rock formation in hydrogeologic maps, which yielded correlation coefficients of 78.3%–88.9%. Overall, the groundwater potential zones of different grades in the study area tended to be stable all year‐round, including the zones of grades I and II. The results of this study highlighted the reliability of predicting groundwater potential based on long‐term series remote sensing data and its usability to local personnel in appropriate groundwater resource planning and management.

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Geological records of South China Sea tsunamis on Penghu Islands, Taiwan

Cited by 12 publications

References 23 publications

Boulder transport and wave height of a seventeenth century South China Sea tsunami on Penghu Islands, Taiwan

Boulder transport and wave height of a seventeenth century South China Sea tsunami on Penghu Islands, Taiwan

A Generic Method to Derive Coastal Bathymetry From Satellite Photogrammetry for Tsunami Hazard Assessment

Groundwater potential mapping based on long time series remote sensing data in Penghu Islands, China

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