[S23P] PM-P

[S23P-09] 2024年日向灘地震直前の地殻変動の相関解析

*田中 宏樹¹、梅野 健¹ (1. 京都大学大学院　情報学研究科)

We report the preliminary results of the analysis of crustal deformation data immediately before the Hyuganada earthquake in 2024. The area is in the Nankai Trough, where slow earthquakes are observed; the association between slow earthquakes and the occurrence of large-scale earthquakes is under discussion [1]. We used the rapid solutions of crustal deformation data at 5-minute intervals published by the Nevada Geodetic Laboratory (NGL) [2,3]. The displacements of observational stations from their reference point, which was set referring to the method of analyzing the crustal deformation data by Bletery and Nocquet [4], are the object of our analysis. To these displacements before the 2024 Hyuganada earthquake, we applied the method of CoRrelation Analysis (CRA) [5,6,7,8], which has been used to detect anomalies in the Total Electron Content (TEC) in the ionosphere before large-scale earthquakes [9] and has also been attempted to apply to crustal deformation data [10,11]. As a result, high correlation values were observed at close stations to the epicenter about two hours before the earthquake. However, after that high value, it gradually decreases as time approaches to the mainshock occurrence. Such a tendency is different from the accelerated increase in [4] and our results of the CRA for a pre-Tohoku-Oki earthquake [12], which may reflect the difference in pre-slip style in these areas. Also, high correlation values were observed sporadically at a distance from the epicenter. We plan to discuss these trends in the variation of correlation values in relation to earthquake occurrence.

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