|Seminar and Symposium at KURCPI
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Research Seminar No.221, 19 July 2022
16:30-, The Interdivisional Education and Research Building, 5th Floorbr
「High-pressure experiment and observation of chlorite in the area where inter-mediate earthquakes occur」
(International Center for Island Studies, Kagoshima University)
Inter-mediate earthquakes occur in the interior of the subduction zone plate (at depths of about 60 to 300 km). These occur in areas where earthquakes should not theoretically occur, and their causes have not yet been clarified. The islands of Kagoshima Prefecture are located along the Philippine Sea Plate. In 1911, an earthquake with a magnitude estimated to be 8.0 occurred there. They have not been verified and cannot be predicted, although there are some strong hypotheses. Since the area where chlorite exists and the area where inter-mediate earthquakes occur are almost the same, we hypothesized that the behavior of chlorite is the cause and conducted an experiment. In this presentation, I want to introduce the structural change of chlorite in the area where inter-mediate earthquake occurs.
Chlorite is a layered mineral. Chlorite is classified into polytypes, which have slightly different properties depending on the way they are layered. It is known that under high pressure conditions, chlorite undergoes a sudden change in the way each layer overlaps one another. Some of these changes are accompanied by polytype changes. Acoustic Emission, a wave similar to seismic waves, occurs more frequently and its energy magnitude increases with this polytype change. In other words, the behavior of chlorite is generating waves like seismic waves. However, since these data were obtained at room temperature, we verified whether this change also occurs under high-temperature and high-pressure conditions.