Japan Geoscience Union Meeting 2025

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[E] Oral

S (Solid Earth Sciences ) » S-GC Geochemistry

[S-GC37] Volatiles in the Earth - from Surface to Deep Mantle

Tue. May 27, 2025 1:45 PM - 3:15 PM 301A (International Conference Hall, Makuhari Messe)

convener:Hirochika Sumino(Research Center for Advanced Science and Technology, The University of Tokyo), Antonio Caracausi(National Institute of Geophysics and Volcanology), Kenji Shimizu(Kochi Institute of Core Research, Japan Agency for Marine-Earth Science and Technology), Takeshi Hanyu(Japan Agency for Marine-Earth Science and Technology, Research Institute for Marine Geodynamics), Chairperson:Antonio Caracausi(National Institute of Geophysics and Volcanology), Kenji Shimizu(Kochi Institute of Core Research, Japan Agency for Marine-Earth Science and Technology), Hirochika Sumino(Research Center for Advanced Science and Technology, The University of Tokyo), Takeshi Hanyu(Japan Agency for Marine-Earth Science and Technology, Research Institute for Marine Geodynamics)

1:45 PM - 2:15 PM

[SGC37-07] Persistent crustal CO2 emissions following the 2022 M6.8 Chihshang earthquake sequence in eastern Taiwan

★Invited Papers

*Ching-Chou FU1, Kuo-Hang Chen1, Kuo-Wei Wu1, Pei-Ling Wang2, Li-Hung Lin3, Hao Kuo-Chen3, Chung-Hsiang Mu1, Vivek Walia4 (1.Institute of Earth Sciences, Academia Sinica, Taiwan, 2.Institute of Oceanography, National Taiwan University, Taiwan, 3.Department of Geosciences, National Taiwan University, Taiwan, 4.National Center for Research on Earthquake Engineering, NARL, Taiwan)

Keywords:2022 M6.8 Chihshang Earthquak, CO2 degassing, Chihshang Fault

On September 17, 2022, a magnitude 6.6 earthquake occurred, followed by a magnitude 6.8 mainshock in Chihshang approximately 17 hours later, along the southern Longitudinal Valley in eastern Taiwan, where the Eurasian and Philippine Sea plates meet. This seismic event caused significant damage to buildings and the surface. In order to investigate the gas-bearing properties of the Chihshang Fault (CSF) zone and gain a better understanding of the degassing behavior, soil gas surveys were conducted to examine gas species and CO2 degassing. Our findings indicate that the observed increase in CO2 flux at the surface after the CS earthquake could be attributed to the release of gases from both deep and shallow sources, with the enhanced permeability of the fault system playing a role in this process. The presence of a heavier 13C isotopic composition provides evidence of an additional contribution of CO2 gas migrating from depth to the surface, a phenomenon that persisted for at least three months after the earthquake. These observations suggest that the CSF system acts as a conduit connecting deep and surface gas reservoirs, with CO2 emissions linked to significant seismic activity. The earthquake-induced microfractures may gradually heal and return to their original state. Based on our estimates, the total natural CO2 degassing around the entire CSF zone is approximately 1200 t/d before the Chihshang earthquake and 2200 t/d after the earthquake. These findings shed light on the dynamic behavior of gas emissions associated with seismic events and provide valuable insights into the degassing processes within the study area.