Tengnan Wang1,2, Yunpeng Wang1,2*
(1State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
2University of Chinese Academy of Sciences, Beijing, 100049, China)
Abstract: The Sichuan Basin is a natural gas-exploiting area with intensive agricultural activities and is adjacent to the active Longmenshan fault zone. Its atmospheric methane field is characterized by long-term increasing trends, seasonal variations, and spatial heterogeneity, with agricultural activities and natural gas exploitation contributing significantly to the regional methane background. In this study, multi-source satellite observations were integrated to investigate atmospheric methane anomalies associated with the 12th May 2008 Wenchuan Mw 7.9 earthquake. Monthly column-averaged dry-air mole fraction of methane (XCH4) observations derived from SCIAMACHY, GOSAT, and Sentinel-5P were combined with eight-day Atmospheric Infrared Sounder (AIRS) data to examine methane variability at different temporal scales. Atmospheric methane anomalies were identified using differential analysis and the Robust Satellite Technique.
The results reveal a coherent multi-scale methane response before and after the earthquake. Monthly methane anomalies first appeared in February 2008, approximately three months before the mainshock, and intensified during the pre-earthquake period. The strongest and most spatially continuous anomalies occurred around the time of the earthquake, followed by a rapid decline during the post-seismic period. Eight-day AIRS observations further captured short-lived and spatially heterogeneous methane fluctuations that were not evident in the monthly averages. Methane anomalies were concentrated along the Longmenshan fault system and exhibited clear fault-dependent characteristics, with the Wenchuan–Maowen fault showing the strongest atmospheric methane response.
These results demonstrate that integrating multi-source satellite observations at different temporal scales provides an effective approach for characterizing earthquake-associated atmospheric methane variability against a complex regional methane background.
Key words: Atmospheric methane; XCH4; Wenchuan earthquake; Longmenshan fault zone; Multi-source satellite observations; Multi-scale observations
Author Profile:
Tengnan Wang, Female, PhD student, mainly engaged in atmospheric methane remote sensing and its applications in environmental and geological studies. E-mail: wangtengnan21@mails.ucas.ac.cn
 
