[S12-P] Poster

[S12-P-04] Characteristics of b-value and TEC changes in Space and Time before the Large Earthquakes in Japan

Takaaki Kobari¹, Peng Han^{1, 2}, ^○Katsumi Hattori¹ (1.Chiba University, Japan, 2.Institute of Statistical Mathematics, Japan)

In recent years, there are many reports on electromagnetic phenomenon preceding large earthquakes. Anomaly of the total electron content (TEC) is one of the most promising anomalies for the short-term earthquake forecast. However, the TEC is disturbed by solar-terrestrial interaction very much. Therefore, it is difficult to discriminate anomalous changes on earthquakes and solar activities easily at the moment. On the other hand, it is reported that the b-value around the epicenter region decreases prior to the large earthquake. In this paper, we investigate the effectiveness of the integrated analyses on the b-value and TEC analysis. We select the 2003, 2008 Tokachi-oki EQs and the 2011 Tohoku-oki EQ at first. As results, we found the variation of b-value has a tendency to decrease for M7class EQs in the analyzed regions and the neighbor's area. For the 2003 Tokachi-oki EQ, we found decrease of b-value 16 days and 2-3days before the main shock. On the other hand, for the TEC anomaly in the Hokkaido region, we found significant increase 2 days before the EQ(M>6.0,D<40 km) using the statistical analysis during 1998-2015. That is, the positive anomaly is dominant, In the case of the 2003 Tokachi-oki EQ, TEC anomaly occurred 2 days before main shock. These results suggest the effectiveness of the proposed method. We have the similar tendency for the 2011Tohoku-oki EQ. Details will be given in the presentation.