Abstract: Taking the case of the iso-pressure heat capacity,the paper has studied the critical singularities of water and its appearing condition in the lithosphere,and discussed the possibility of triggering earthquakes by the coupling of the critical singularities and fractures.There are first-order and second-order phase transitions of water in the lithosphere.When the phase transitions appear,the physic-chemical characteristics of water will also change,and the change will be huge at the critical point of water,namely the critical singularity.Because of the critical singularity of water,some physic-chemical characteristics,such as the heat capacity and the coefficients of thermal expansion and compression,will approach infinity.According to the Mie-Grüneisen formula(∂P/∂T)^V=γρC^V),the infinity of the heat capacity of water will cause the thermal-pressure to become the infinity too.Instantaneously,the pressure will sharply increase and trigger the earthquake.But the temperature is related to pressure according to the geothermal curve of the lithosphere.Calculated with the normal geothermal gradients(15～35℃/km)and the geopressure gradients(0.025～0.03GPa/km),the depths of critical temperature and critical pressure of water are respectively 24～10km and 0.88～0.73km.It means there are no places where temperature and pressure can simultaneously approach the critical values of water in the lithosphere if there are no fractures.In such case,the critical singularity cannot appear.The fractures can cause the pressure to decrease to the critical pressure of water,so the temperature and pressure will approach to the critical values of water in some place in the lithosphere.The condition of appearing the critical singularity of water is the temperature and pressure simultaneously approaching the critical values of water.The result of the research has proposed that the coupling between the critical singularities and fracture is essential to trigger earthquake.

Key words: water, phase transition, critical singularities, fracture, earthquake

摘要： 以等压热容为例,研究岩石圈中水的临界奇异性及出现的条件,探讨岩石圈中水的临界奇异性与断裂耦合作用触发地震的可能性。岩石圈中水存在一、二级相变,相变时水的物理化学性质将发生明显改变,在临界点处表现出奇异性,如热容、膨胀系数和压缩系数等将趋于无穷大,按照Mie-Grüneisen方程((∂P/∂T)^V=γρC^V),热容无穷大时将导致热压也趋于无穷大,压力将瞬时剧增。但水的临界奇异性出现的条件是温、压同时趋于临界值,在岩石圈中温、压是相互关联的,按照正常的地温梯度(15～35℃/km)和地压梯度(0.025～0.03GPa/km)计算,达到水的临界温度和压力的深度分别是24～10km和0.88～0.73km,即在岩石圈中若没有断裂的存在时则不可能同时达到水的临界温度和临界压力,不可能出现临界奇异性。断裂使压力降至水的临界压力,使得在岩石圈中某处温度和压力可同时达到水的临界值而出现奇异性,水的临界奇异性和断裂的耦合导致热压剧增,可能触发地震。

关键词: 水, 相变, 临界奇异性, 断裂, 地震