Investigation of earthquake thermal precursors in active tectonic regions of the world

ABSTRACT Intensive physical/chemical changes take place in earthquake preparation zone prior to major earthquake events. These changes result in anomalous variations of atmospheric parameters. In this study, anomalous variations of Surface Latent Heat Flux (SLHF) and Air Temperature (AT) are investigated prior to 17 major earthquake events with magnitude ≥ 5.3 Mw in active tectonic regions of the world for the period from 2004 to 2020 using InterQuartile Range (IQR) and Hierarchal Clustering (HC) statistical techniques. Studied earthquakes are selected from subduction, transform and intraplate locations. The results clearly show anomalous variations in the SLHF and AT atmospheric parameters few days to few weeks prior to the occurrence of the earthquake event. The Honshu earthquake event is captured 54 days prior to the event using SLHF data, whereas Bella Bella earthquake event is observed 39 days prior to the event using AT data. Best anomalies using both SLHF and AT are identified for Pasni and Norcia earthquake events, whereas lowest anomalies using both SLHF and AT are identified for Nsunga and Puerto Quellon events. The anomalous variations of SLHF and AT prior to the earthquake event show a definite precursor pattern. Strong anomalies are observed in subduction/thrust regime whereas, minimum to moderate anomalies are observed along strike slip faults. This study determined the threshold values of 59.52 W/m2 and 2.87 K for SLHF and AT respectively. The HC revealed more than 70% similarity among earthquakes based on depth, magnitude, SLHF and AT. Mechanism of energy exchange between lithosphere and atmosphere can be understood by analyzing significant rise in SLHF and AT. It is essential to monitor these variations continuously to properly identify earthquake related anomalies.