Identification of Thermal Anomalies in Active Volcanoes Using Google Earth Engine and Multi-Spectral Satellite Images

In this work, we applied Landsat 7 satellite images to explore the most active hydrothermal alteration zone of the Ilamatepec volcano during the period of its eruption in October 2005, and used these images together with ASTER sensor data to explore the changes of heat loss in the thermally active area of the Ilamatepec crater from 2005 to 2006. Multiple methods were used to map the hydrothermal alterations in the area including band ratio, principal component analysis, Crosta techniques and color composite. The normalized difference vegetation index (NDVI), emissivity and land surface temperature (LST) values were also obtained, with which the radiative heat flux (RHF) for the study area was derived. The maximum LST values were estimated to be 35 °C, 37 °C and 32 °C for the study dates. The maximum RHF values were 125 W/m2, 137 W/m2 and 104 W/m2 for these same dates. The intensity of thermal unrest in the study area increased due to the eruption but showed a tendency to decrease for the last month of observation.