[MIS09-04] Seismo-conductivity anomaly associated with the 2017 MS 7.0 Jiuzhaigou earthquake
キーワード：Parkinson vector, Seismo-conductivity anomalies, The Jiuzhaigou earthquake
Changes of underlying conductivity around hypocenters are considered to be a potential source of seismo-electromagnetic anomalous phenomena. In this study, Parkinson vectors computed by 3-component geomagnetic data recorded at nine geomagnetic stations via magnetic transfer function are utilized to monitor the conductivity changes during the 2017 MS 7.0 Jiuzhaigou earthquake. To mitigate artificial disturbances, low noise data during the 23:00 – 5:00 LT are utilized. We compute the background distribution and monitoring distribution using the azimuth of the Parkinson vectors at 0.005 – 0.01 Hz at each station within a one-year of 2017 and a 15-day moving window, respectively. The background distribution is subtracted from the monitoring distributions to mitigate the influences of underlying inhomogeneous tectonic structures. The obtained difference distributions binned by 10° within 400 km from each station are superimposed during 45 days before and after the earthquake to construct integrated maps. The superimposition results show that an intersection of seismo-conductivity anomaly is distributed in the area (i.e., 104.00°E, 33.86°N) about 70 km away from the epicenter 17 days before the earthquake. The anomaly becomes unclear about 7 days before and remains insignificant after the earthquake. These results suggest the changes of underlying conductivity near the hypocenter can be simultaneously detected by numbers of magnetometers before the Jiuzhaigou earthquake. The variations of the seismo-conductivity anomaly during the earthquake lights on a promising candidate of the pre-earthquake anomalous phenomena.