According to K. S. Jayaraman
Earth emits a burst of carbon monoxide (CO) a few days before an earthquake, according to geophysicist Ramesh Singh. […] “The carbon monoxide shows enhancement in concentration a few days prior to the earthquake,” Singh said. […]
Singh said that CO levels were taken by an instrument onboard NASA’s Terra satellite — launched in 2009 — circling the earth in a polar orbit at a height of 705 km. The instrument measures CO concentrations at different heights and also computes the total amount of the gas in a vertical column of air above the earth surface.
Analysis of the satellite data showed a large peak in CO concentrations during January 19 and 20 — a week before the main earthquake event. On January 19, the total CO in the vertical column was also higher than usual. After the 26 January earthquake the concentration of the gas dropped.