doi:10.1038/nindia.2010.13 Published online 15 February 2010
Earth emits a burst of carbon monoxide (CO) a few days before an earthquake, according to geophysicist Ramesh Singh. He and co-workers from France and the United States report that this gas could be used as one of the precursor signals for an earthquake early warning system.
The scientists used data from an American satellite and analysed changes in carbon monoxide at different altitudes. "The carbon monoxide shows enhancement in concentration a few days prior to the earthquake," Singh said.
Singh, who was formerly with the Indian Institute of Technology in Kanpur, is currently in the physics department of Chapman University in California, USA. The project was funded by the Indo-French Centre for the Promotion of Advanced Research in New Delhi.
The researchers discovered the connection between CO emission and earthquake by analysing satellite remote sensing data collected around the time when a 7.6 magnitude earthquake shook Gujarat in western India nine years ago killing about 20,000 people and rendering thousands homeless.
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.
According to the scientists, CO gas is forced out of the earth due to the build up of stress prior to the earthquake "influencing the hydrological regime around the epicentre."
Singh said an anomalous increase in land surface temperature a few days prior to Gujarat earthquake — as inferred from the data of NASA's other satellite MODIS — is also related to the CO emission. "The increase of column CO and concentrations of CO may have enhanced the land surface temperature," he said.
"The anomalous changes in CO concentrations prior to the main earthquake event and enhancement of temperature of the earth surface observed from MODIS satellite data give an indication of coupling between land and atmosphere," the scientists report. Singh said observation by other researchers of a sudden increase in water vapour in the atmosphere and changes in the ionosphere a few days prior to the Gujarat earthquake all seem to be connected.
According to the report, all these observations including the latest discovery of CO emission show the existence of a 'strong coupling' between land-atmosphere-ionosphere. "The integration of all these parameters in a seismically active region therefore looks a potential approach to understand earthquake processes and may provide reliable information about an impending earthquake," the researchers conclude.