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

摘要

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%), CO_2 (2.0%) and He (0.2%). Concentration of the radioactive gas ~(222)Rn is relatively high (7500 Bq/m~3). This paper discusses the experimental methods adopted to continuously monitor He, CH_4, CO_2 and ~(222)Rn 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.