Investigation of possible tsunami events on the eastern coast of Taiwan: case studies of Lu-Ye, Changping, and Tulan

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1 Investigation of possible tsunami events on the eastern coast of Taiwan: case studies of Lu-Ye, Changping, and Tulan Speaker : FX. Anjar Tri Laksono Adviser : Louis Loung-Yie Tsai Date : October 19,

2 Outline Study area and geological background The location of sampling sites Aims of this study Literature review The result of previous studies. Geological, topographic, and bathymetric maps. Data description Earthquake records Primary data Methodology Preliminary result Conclusion 2

3 Study area and geological background N Fig.1. Location of the study area on the map (Google Earth, 2017) 3

4 Aims of this study Three aims of investigation of possible tsunami events on the eastern coast of Taiwan: To understand the history of tsunami on the eastern coast of Taiwan (age, frequency, and period). To determine the distribution pattern of tsunami sediment layers. To describe inundation distance, run-up, and flow height. 4

5 Literature Review The results of research A big sea wave struck Chenggong in 1850 AD. There were no tsunami deposit on marine terraces of Chenggong. There were tsunami deposits on marine terraces of Chenggong. Chenggong tsunami occurred in It was related to the 1771 tsunami south of Ishigaki Island. Three coral boulders were found resting on the Holocene coral terrace on the Jiupeng coast. Paleotsunamis occurred several times since the mid- Holocene high stand of sea level. References Abe, 1938, as cited in Ando et al., 2013 Hsieh and Rau, 2009, as cited in Lallemand et al., 2016 Ota et al., 2011 Ando et al., 2013 Matta, 2013 Ota et al.,

6 The comparison of tsunami research on eastern coast of Taiwan between previous studies and this study Previous studies Recent study Simulation approach (Ando et al., 2013) Observation and experiment approaches Boulder analysis study (Matta, 2013; Ota et al., 2015). Marine terrace deposits Study area in offshore (Lallemand et al., 2016) Study area in onshore 6

7 N (A) (B) Fig.2. (A) Geological map of the Coastal Range (Chen and Wang, 1997). (B) Topographic and bathymetric maps (Lallemand et al., 1997) 7

8 Data Description Data Primary data Advanced data Outcrops observation Sedimentary rocks Regional geology Topography and bathymetry maps Earthquake records 8

9 Earthquake Records Table 1. Earthquake and tsunami records in Taiwan since 1677-present (USGS, 2017). 9

10 Primary Data Marine sand deposit (A) (B) Fig. 3. (A) Outcrop and (B) a sample of sedimentary rock at sampling site 20 (Tulan area). 10

11 Methodology Marine sand Beach sand (Fig. 11 D) Beach gravel Fluvial gravel and transported material (A) Fig. 4.(A) Observation at site 14 (Lu-Ye area). (B) Sand composition counting experiment (B) 11

12 Fig. 5. Fiji and ProSim free softwares for petrography analysis 12

13 (A) Loose sediments (B) Shaker machine (C) Solid microscope (E) Planktonic foraminifera (E) Planktonic foraminifera in the glass Fig. 6. Fossil analysis processes 13

14 Preliminary Results North North Beach gravel Marine sand (target) Fluvial gravel Marine sand (target) Beach gravel Fluvial gravel Alluvial fan Alluvial fan (A) Modern nearshore sand (Fig. 11 B) (B) Fig. 7. Marine terraces at sampling site 1 (A) and 13 (B) Lu-Ye. 14

15 North E D C B A A Fig.8. The intercalation between marine sand, fluvial gravel, and beach gravel at sampling site 24 (Changping). (A). Medium sand, (B) very coarse sand, (C) coarse sand, (D) beach gravel, (E) fluvial gravel. 15

16 Beach sand (Fig. 11 C) Fig. 9. Marine terrace at sampling site 25 (Changping Harbour area). 16

17 Beach gravel Mud Debris-flow gravel Beach gravel (Fig. 11 A) Tsunami sediment candidate (B) Debris-flow gravel (A) (C) Fig. 10. Marine terrace at sampling site 26 (A), 29 (B), and coral boulder at sampling site 15 (C), Changping.

18 Pelecypod shell Fig. 10. Mollusca shells at marine terrace of Tulan (sampling site 19). 18

19 Qp Ls Qp PX Qm Qp Qp (A) (B) Qp Lm Qp Qp Qp Qp (C) Lm Fig. 11. Thin sections of sedimentary rock from sampling sites 29 (A), 13 (B), 25 (C), and 14 (D). Qp: polycrystalline quartz, Qm: monocrystalline quartz, : volcanic rock fragment, PX: Pyroxene, and Lm: metamorphic rock fragment. (D) Qp 19

20 Fig. 12. Sand composition counting from Lu-Ye (sampling sites 1 and 13) and Changping (sampling sites 3, 8, 9, and 12). 20

21 Chamber Chamber (A) Suture (B) (C) Suture Suture Suture Suture Chamber Chamber Chamber (D) Fig. 13. (A) Neogloboquadrina dutertrei, (B) Orbulina universa, (C) Globigerinoides ruber, (D) Trilobatus sacculifer, (E) Uvigerina auberiana, (F) Globigerinoides diminutus (E) (F) 21

22 Biozonation 22

23 Paleobathymetry 23

24 Fig. 14. Marine zone (Nagy et al., 2000). 24

25 Conclusions There are 5 facies: alluvial fan, fluvial gravel, beach sand, beach gravel, and marine sand. Biozonation analysis exhibits that the age of marine deposits in Lu-Ye, Changping, and Tulan are Pleistocene-Holocene. Paleobathymetry of marine sand deposits depicts outer neritic. There were some super flood event deposits on the marine terraces of Lu-Ye, Changping, and Tulan. 25

26 Future Works Sand composition counting on marine terraces of northern Changping and Tulan. Construct stratigraphic columns. Classify the type of super flood events. Identify the age of super flood events (using carbon dating data). Inundation distance, run-up, and flow height descriptions. 26

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