[M-IS10] Interdisciplinary studies on pre-earthquake processes

[MIS10-P05] Multi-channel singular spectrum analysis of soil radon concentration, Japan

*服部 克巳^1,2,3、根本 和秀⁴、小島 春奈⁴、北出 明嗣⁴、金子 柊⁵、吉野 千恵¹、茂木 透¹、Ouzounov Dimitar⁶ (1.千葉大学大学院理学研究院、2.千葉大学環境リモートセンシング研究センター、3.千葉大学災害治療学研究所、4.千葉大学理学部、5.千葉大学大学院融合理工学府、6.チャップマン大学)

キーワード：Multi-channel singular spectrum analysis、soil radon concentration、soil radon flux、local seismic activity、precipitation

Recently, there are many papers on electromagnetic pre-earthquake phenomena such as geomagnetic, ionospheric, and atmospheric anomalous changes. Ionospheric anomaly preceding large earthquakes is one of the most promising phenomena. Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model has been proposed to explain these phenomena. In this study, to evaluate the possibility of chemical channel of LAIC by observation, we are developing soil and atmospheric Rn observations using an α-ray detector in Chiba-Ibaraki area to investigate the relationship between earthquakes and Rn emissions from the ground. We have installed sensors for atmospheric electric field, atmospheric ion concentration, atmospheric Rn concentration, soil radon Rn concentration (SRC), and weather elements, Since the atmospheric electricity parameters are very much influenced by weather factors, it is necessary to remove these effects as much as possible. In this aim, we apply the MSSA (Multi-channel Singular Spectral Analysis) to remove these influences from the variation of SRC and estimate the soil Rn flux (SRF). We investigated the correlations (1) between SRF and precipitation and (2) between SRF and the local seismic activity around Asahi station. The preliminary results show that SRF was significantly increased by heavy precipitations of 20 mm or more in total for 2 hours. We proposed two types of models, a rainwater load model and a rainwater infiltration model, and it is appropriate for both models to work and (2) between SRF and local seismicity within an epicenter distance of 50 km from the station.