[M-GI31] Introduction to forensic geoscience

[MGI31-P01] Forensic geohazard profiling of the pyroclastic density current hit Onokoba Elementary School site (Unzen volcano, Japan)

*Balazs Bradak¹, Christopher A Gomez^1,2, Yoshinori Shinohara³, Norifumi Hotta⁴ (1.Faculty of Maritime Sciences, Kobe University, Japan , 2.Faculty of Geography, Univ. Gadjah Mada, Yogyakarta, Indonesia, 3.Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan, 4.Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan)

Keywords:forensic geology, forensic geohazard, ground penetrating radar, pyroclastic density current

Forensic geohazard, a discipline of forensic geology, is one of the novel and developing fields of geosciences, with a focus on the deeper understanding of the characteristic of natural hazards and their way of distraction. One of the goals of forensic geohazard studies is the analysis of the disaster-hit objects and the damage of the natural hazards on the remains. This way forensic geohazard profiling contributes to future disaster prevention and hazard mitigation. Recently, the remains of Onokoba Elementary School (Shimabara, Japan) and its neighbourhood, a location, hit and destroyed by one of the biggest pyroclastic density currents during the 1990-1995 active period of Unzen volcano were revisited and investigated by ground penetrating radar (GPR), a tool often used in various fields of geology. During the analysis of radargrams gained by high-resolution GPR measurements, executed in locations with known pre- and post-eruption condition, various pre-eruption surfaces and buried objects were able to be identified, such as a swimming pool, filled with debris, a concrete sidewalk and footpath, and the buried remains of a smaller building. As it is shown by this study, systematic GPR investigation may help to identify debris cowered objects and holes, altogether with the basic lithological characteristics of the volcaniclastic sediments, which accumulates and buries the target location. Although the presented GPR investigation was focused on the remains of a three-decade old eruption, we believe that the results support the future application of GPR in on-site forensic hazard investigations, post-disaster research and long-term hazard mitigation in the cases connected to pyroclastic flows.