A geochemical approach to earthquake reconnaissance at the Baratang mud volcano, Andaman and Nicobar Islands

Variations in the relative composition of constituent gases coming out of the mud volcano near Jarwa Creek in Baratang Island, Middle Andaman, are discussed on the basis of regional tectonic settings and seismo-geochemical features. The most abundant gas is CH4 (55.7 vol.%) followed by N2 (32.2%), O2 + Ar (9.9%), CO2 (2.0%) and He (0.2%). Concentration of the radioactive gas 222Rn is relatively high (7500 Bq/m3). This paper discusses the experimental methods adopted to continuously monitor He, CH4, CO2 and 222Rn with a view to identify pre-seismic gas concentration anomalies associated with regional seismic occurrences. Results related to this gas-geochemical monitoring are presented with a purpose to develop ability in ascribing a distinct geochemical anomaly to a particular seismic activity in the region.

► Earthquake precursory signals monitoring at Baratang mud volcano, India. ► Baratang mud volcano gas comprises of CH4, N2, O2, Ar, CO2, He & 222Rn. ► 222Rn anomaly observed at Baratang 13 days prior to an earthquake (4.7 M).