Spatial and temporal variations of total column of CH 4 and CO (TotCH 4 and TotCO) associated with the 12 May 2008 Wenchuan and 20 April 2013 Lushan earthquakes in western Sichuan, China were investigated using satellite data from AQUA AIRS in order to understand the lithospheric and atmospheric interactions during the seismic activity. The Wenchuan M S 8.0 and Lushan M S 7.0 earthquakes occurred in the Longmenshan fault zone. It was observed that large amounts of gases emitted from the earth's crust into the atmosphere before, during and after the earthquakes. The anomalies of TotCH 4 and TotCO occurred along the fault zone, and the peak values were found at the intersection areas where the crust stress approached the maximum. Furthermore, temporal anomalies of TotCH 4 and TotCO occurred during and after the Wenchuan earthquake, but 3 months before the Lushan earthquake. The anomalies related to the Lushan earthquake could be partially attributed to the Wenchuan earthquake because of the seismotectonic changes and fractures in the crust produced by the Wenchuan earthquake.

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A continuous GPS array across the southern segment of the Longmen Shan fault zone recorded the deformation during the process of the Lushan M S 7.0 earthquake that occurred on April 20, 2013. Such data can provide meaningful information regarding the dynamic evolution of crustal deformation in the seismogenic zone. Our studies have shown that the occurrence of the Wenchuan earthquake led to the loading of compressive and sinistral shearing strain on the southern segment of the Maoxian-Wenchuan fault, whereby the extrusion strain accumulated at a greater rate than before the Wenchuan earthquake. The strain time series in the seismogenic zone revealed that the principal compression strain rates decreased from west to east in the direction of N30°-45°W. Furthermore, the area to the east of Beichuan-Yingxiu fault behaved as a zone of compressive deformation with obvious sinistral shearing deformation. The surface strain and the first shearing strain time series decreased with time, while the area to the west of the Beichuan-Yingxiu fault behaved as a zone of dextral shear deformation that increased with time. Furthermore, the regional deformation field before the Lushan earthquake showed that the rate of extrusion strain accumulation in the southern segment of the Longmen Shan fault zone was obviously larger than before the Wenchuan earthquake. Moreover, the sinistral shearing strain accumulated in the area of the southern segment of the Maoxian-Wenchuan fault. Based on the above analysis, we consider that the eastward movement of the Bayan Har block increased considerably following the Wenchuan earthquake, which enhanced the accumulation of compression strain in the southern segment of the Longmen Shan fault zone.Lushan M S 7.0 earthquake, GPS observations, GPS baseline time series, strain time series Citation: