Historical Tsunamis of Taiwan in the Eighteenth Century: the 1781 Jiateng Harbor Flooding and 1782 Tsunami Event

This research aims to study two of the historical tsunamis occurred in Taiwan during the 18th century and to reconstruct the incidents. The 1781 Jiateng Harbor Flooding, recorded by the Chinese historical document, Taiwan Interview Catalogue, took place on the southwest coast of Taiwan. On the other hand, the 1782 Tsunami was documented in foreign languages, with uncertainties of the actual time. Reasoning these historical events requires not only carefully examining the literature records but also performing the scenarios that match the descriptions. The Impact Intensity Analysis (IIA) is employed to locate possible regions of tsunami sources in order to reproduce the events. Numerical simulations based on the Cornell Multi-Grid Coupled Tsunami Model (COMCOT) analyze the influence of different types of tsunami generated both by submarine mass failures and seismic activities. Numerical results indicate that the source of the 1781 Jiateng Harbor Flooding is located very possibly at the South South-West side of Taiwan. However, simulation results and historical records put the existence of the 1782 Tsunami in doubt, and the possibility of storm surges could not be ruled out.

Tsunamis boulders on the rocky shores of Minorca (Balearic Islands)

Large boulders have been found on marine cliffs of 24 study areas of Minorca, Balearic Archipelago. These large imbricated boulders, of up to 229 tonnes, are located on platforms that conform the rocky coastline of Minorca, several tenths of meters from the edge of the cliff, up to 15 m above the sea level, and kilometres away from any inland escarpment. They are mostly located on the southeast coast of the island, and numerical models have identified this coastline as a high tsunami impact zone. The age of the boulders in most of the studied localities show a good correlation with historical tsunamis. Age of the boulders, direction of imbrication and estimation of run-up necessary for their placement, indicate dislodging and transport by North Africa tsunami waves that hit the coastline of Minorca.