[M-IS04] Interdisciplinary studies on pre-earthquake processes

[MIS04-12] Soil radon and ionospheric TEC anomalies before the 2022 M6.8 Chihshang Earthquake in eastern Taiwan

★Invited Papers

*Ching-Chou FU¹, Hau-Kun Jhuang¹ (1.Institute of Earth Sciences, Academia Sinica)

Keywords:radon, TEC, Chihshang earthquake

We present a critical analysis of the observations and interpretations related to the 2022 Chihshang earthquake that occurred on September 17, 2022, in eastern Taiwan. This work comprehensively investigated the different parameters related to the lithosphere and ionosphere, including soil radon gas and total electron content (TEC). The previous significant increases in soil radon were often detected at CS station before the large earthquake, which occurred in eastern Taiwan along the southern Longitudinal Valley, suggesting that anomalies in radon provide a good indicator for exploring earthquake precursors in this region. The result shows significant increases in soil radon were found one month before the earthquake. The persistence of the TEC anomalies from September 5 to 12, which were identified by two different methodologies around the Taiwan area to be the pre-earthquake signals, was observed. Furthermore, a higher value of CO2 flux in the area was found after the earthquake, which can be interpreted as an extra contribution of the gas sources from depth or the increased permeability of the fault system. These joint observations have revealed that all these anomalies are considered short-term precursors, which can be explained by the theoretical mechanism of lithosphere–ionosphere coupling (LIC).