Astaneh fault is one of the active and seismic faults in the southern part of eastern Alborz. Performance of seismic faults in carbonate rocks and favorable conditions causes the change in Calcium Carbonate (CaCo3) and its conversion to Calcium Oxide (CaO) or its thermal decomposition. If the environment is suitable for this deformation, after initial deformation, the primal volume is reduced, leaving the space available for depletion between deformed particles, which can be used as a key for this earthquake slip. During the Astaneh fault at the location where the fault occurred in the carbonates, after sampling the fault core and fault gouge, and photographing and studying them by SEM electron microscopy, the presence of Co2 exit bubbles and the reduction of Calcium Carbonate (CaCo3) volume caused by the earthquake slip heat created was observed at the nanoscale and micro level. After observing the thermal decomposition of Calcium Carbonate (CaCo3) in the fault gouge, the reduced volume of particles was calculated from the earthquake slip heat. With the proportion between this volume reduction and the temperature causing it the temperature resulting from the seismic slip causing this deformation is estimated for the sampling location and fault surface

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