Abstract: The anomalies of TotCH4 and TotCO associated with the 15 April 2015 Alashan Zuoqi M_S5.8 earthquake were discussed based on the satellite hyper-spectrum data. The background in monthly and anomaly-index of TotCH4 and TotCO were calculated from AIRS standard 3 level product data in recent years (2003—2012). The results showed that the TotCH4 and TotCO backgrounds in the study area presented obviously seasonal variations in temporally. Spatially, the distributions of TotCH₄ and TotCO were affected by the tectonic geological background and topographic landform. The high values of TotCH₄ and TotCO were located in Yinchuan, Jilantai and Hetao fault-sinking basins. TotCH4 anomaly appeared linearly along western edge of Ordos fault in April, while TotCH₄ appeared in oil-gas-bearing basins on both sides of the epicenter about 1 week before the major shock with the maximum anomaly index reached 6. TotCO anomaly appeared when and after the main shock, and lasted for two weeks. And the spatial distribution of TotCO anomaly was consistent with the CH₄. There was a close relationship between CH₄ and CO. The CO anomaly was partly derived from the CH₄ oxidation.

Key words: CH₄, CO, Anomaly-index, earthquake