CO, O₃and CH₄Anomalies Of Remote Sensing Geochemistry Occurred Before And After Great Earthquakes

Great earthquakes usually cause great calamity. It is the pressing social needs tomitigate earthquake disaster by monitoring and predicting earthquake. Plenty of gases(CO, CO2,H2, Hg, He, Rn and CH4) emit along the fault zones from the solid earth tothe atmosphere under the action of tectonic stress before and after the earthquakes. Tomonitor the variation of gas emission from the seismic zones using the hyper-spectralremote sensing technique developed in recent years is not only scientificallysignificant in investigating genetic mechanisms of the gas anomalies duringearthquake activities, but also provides new technique of earthquake monitoring andfavors mitigating earthquake disaster.The monthly background fields (values) of total column CO, O3and CH4VMRwere calculated using the AIRS data from2003to2012. Anomalies of total columnCO, total O3and CH4VMR before and after113earthquakes with M>7.0and focaldepth less than35km, which occurred throughout the world from2003to2012, wereextracted based on the background data. Consequently, the characteristics andmechanisms of the obtained gas anomalies were discussed.The results can be briefly summarized as following:(1) It was found that63.7%of the studied earthquakes were accompanied withCO, O3and/or CH4anomalies. The data showed that the54studied cases (47.8%oftotal) were accompanied with the CO anomalies, of which the strength had a range of0.88~11.92×1017molecules/cm-2;65studied earthquakes (57.5%) with the O3anomalies with an abnormal strength range of1.72~74.56DU; and34earthquakes(30.1%) with CH4anomalies with an abnormal strength range of1.17~5.05×10-8.(2) The anomalies of CO and O3concentrations and CH4VMR appeared mostlyin3months before the earthquakes, while appropriately a quarter of the gas anomaliesappeared in the month of earthquake occurrences or after the events. In general, thedurations of total CO and O3anomalies ranged from1to12months (more than6months mostly). However, the durations of CH4VMR anomalies were usually lessthan6months. (3) The geochemical anomalies of CO and O3and CH4VMR associated withearthquakes can be mainly attributed to the gas emission from the lithosphere duringthe earthquake activities as well as the physical and chemical alteration of the emittedgaseous components in the atmosphere.(4) CO, O3and CH4altered by chemical reactions. Both CO and CH4acted asthe precursors of O3under the OH catalysis. The results are conducive tounderstanding the process of seismic activities.