Geochemical and heavy mineral signatures of marine incursions by a paleotsunami on the Miyazaki plain along the Nankai-Suruga trough, the Pacific coast of southwest Japan

Watanabe, Takahiro   ; Kagami, Saya   ; Niwa, Masakazu   

Miyazaki plain on the Pacific coast of southwest Japan along the Nankai-Suruga trough was also affected by marine incursion by the past interplate earthquakes and tsunami. Notably, paleotsunami deposits were found on the area and important clues to reconstruct the past marine incursion by earthquakes and tsunami. However, geochemical and heavy mineral analyses on the area were not enough to characterize the deposits. Therefore, quantification analyses with high-time resolution by portable energy dispersive X-ray fluorescence spectrometry (portable XRF), scanning by X-ray analytical microscope (XGT), statistical analyses for chemical components, and heavy mineral analyses were performed for the paleotsunami deposits of the Kanbun Hyuganada earthquake with the age of 1662 CE from the south Miyazaki plain in this study. Based on our research, we summarized as follows: (1) increases in the titanium normalized values of S, Ca, Fe and Sr, and depletions of Si, K, and Rb were observed in the deposits, (2) Zr accumulations and heavy minerals such as zircon were found in the deposits caused by possible high energy tsunami, and (3) cluster analyses of the geochemical data from the core by portable XRF distinguished the paleotsunami deposits on the Miyazaki plain.