Influence of permeability and porosity on the thermal energy produced in a seismic fault: implications for the seismic cycle

Abstract We investigate the impact of permeability and porosity on the thermal energy generated by friction within seismic faults under thermal pressurization, and its potential implications for the seismic cycle. We first look at the co-seismic slip phase and then simulate the instabilities that precede earthquakes by considering a solid-slip system with one degree of freedom and a linear friction model for study heat flow under high-pressure conditions. Our results show that during the co-seismic slip phase, an increase in permeability will lead to a reduction in fluid pore pressure and consequently to an increase in temperature and thermal energy at the same time. Conversely, an increase in porosity yields the opposite effect. During the nucleation phase, reduced permeability and increased porosity lead to a decreased frequency and an extended recurrence interval of pre-earthquake instabilities, respectively. We therefore postulate that thermal-energy variation constitutes an indicator of major earthquake occurrence, as it reflects changes in stress state, disturbances, and instabilities taking place at seismogenic depths and can help in the detection of earthquake hazards.