Thermal Anomalies in Relation to Earthquakes in India and its Neighbourhood

Thermal anomalies based on satellite and surface meteorological data in the epicentral region prior to a few earthquakes in India and elsewhere have raised a question whether such inferences can be relied upon keeping in view larger meteorological variability associated with synoptic weather changes. This article examines outgoing longwave radiation (OLR) data by INSAT over Sikkim region to find whether any anomaly developed prior to the earthquake of September 2011 (M_w 6.9). Similar study was made using surface meteorological data (weather observatories or NCAR grid point values) in the meizoseismal areas of Bhadrachalam (1969, m_s 5.7), Kinnaur (1975, m_s 6.9), Bihar-Nepal (1988, m_s 6.9), Uttarkashi (1991, m_s 6.8), Latur (1993, m_s 6.1), Jabalpur (1997, m_s 5.6), Chamoli (1999, m_b 6.5), Bhuj (2001, M_w 7.6) and Muzaffarabad (2005, M_w 7.6) earthquakes. The OLR data from INSAT were also examined during heat-wave conditions prevailing over northern India in summer during non-seismic conditions. It was found that there was no significant thermal anomaly prior to any earthquake in the Indian region. It has been shown that the precursory thermal anomaly reported in earlier studies for Bhuj (2001), Muzaffarabad (2005), Jabalpur (1997) and Latur (1993) earthquakes was misinterpreted since the rise in surface temperature (if any) was found to be well within the meteorological variability caused by synoptic weather conditions. Persistent heat-wave conditions causing very large thermal anomaly for several days in northern India raise false alarms. The synthesis of the results presented in this study should desist geoscientists from considering thermal anomalies as earthquake precursors.