Differential thermal expansion of pore fluids: Fracture propagation and microearthquake production in hot pluton environments

摘要: Thermally induced differential expansion between fluid in isolated pores and enclosing minerals decreases effective pressure at the pore-mineral interface. With a sufficient increase temperature, becomes equal to tensile strength, rock fractures. The ratio of coefficient thermal compressibility for pore defines nature this process. Finite element computations indicate that thermally hydraulic fracturing host rocks is inevitable hot pluton environments. A front propagates away from cooling plutons rate 100 cm/yr first 400 years 1 105 years. Fluid energy release upon can produce microearthquakes measurable magnitude. Predicted frequencies vary 4×103 events/day 5×103 500 Estimates ambient pressures show continually increases with depth geothermal gradients less than 10°C/km. For larger but eventually decreases.