On Shear Stresses, Temperatures, and the Maximum Magnitudes of Earthquakes at Convergent Plate Boundaries
On Shear Stresses, Temperatures, and the Maximum Magnitudes of Earthquakes at Convergent Plate Boundaries
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DOI：
10.1029/2018jb015907
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发表时间：
2018-08-01
影响因子：
3.9
通讯作者：
England, Philip
中科院分区：
文献类型：
--
作者：
England, Philip
存在表面热流约束的九个俯冲界面上的表观摩擦系数Mu‘落在小于或类似于Mu’小于或类似于0.07的范围内。逆冲断层地震最大深度以上的地表热通量Q(T)落在一个很小的范围内，这意味着界面上从地震滑动到无地震滑动的转变发生在一个温度T-T，这取决于它的深度Z(T)。对于Q(T)接近40 mW/m(2)的平均值，T-T类似于z(T)×12摄氏度/公里。由另外82条跨俯冲带的地震活动剖面确定的逆冲-断裂地震的最大深度，显示出系统地依赖于会聚速率和下降板块的年龄，这也与这些带的Q(T)的窄范围一致。解析表达式将Mu‘与z(T)、Q(T)和俯冲参数联系起来。将这一关系应用于82个剖面，得到了u‘=0.07+/-0.01。如果俯冲界面上的主要热源是地震期间的摩擦加热，剪应力受到孔隙流体的热压作用的限制，那么这个范围的狭窄就可以解释。表观摩擦系数随地震中表示的相对运动的比例变化不大。要么是地震滑动和无地震滑动的表观摩擦系数难以区分，要么是地震活动率历史上较低的地区容易发生尚未记录到的大地震。
Apparent coefficients of friction, mu', on nine subduction interfaces for which surface heat flux constraints exist fall in the range 0.05 less than or similar to mu' less than or similar to 0.07. Surface heat flux above the maximum depth of thrust-faulting earthquakes adjusted for radiogenic heat production, Q(T), falls in a narrow range, implying that the transition from seismic to aseismic slip on the interface takes place at a temperature, T-T, that depends upon its depth, Z(T). For the mean value of Q(T) similar to 40 mW/ m(2), T-T similar to z(T) x 12 degrees C/km. The maximum depth of thrust-faulting earthquakes, determined from a further 82 profiles of seismicity across subduction zones, exhibits a systematic dependence on convergence rate and the age of the descending plate, which is consistent with a narrow range in Q(T) for these zones also. An analytical expression links mu' to z(T), Q(T), and the subduction parameters. Application of this relation to the 82 profiles gives mu' = 0.07 +/- 0.01. The narrowness of that range can be explained if the primary source of heat on the subduction interface is frictional heating during earthquakes with shear stresses limited by thermal pressurization of pore fluids. Apparent coefficients of friction exhibit insignificant variation with the fraction of the relative motion that is expressed in earthquakes. Either the apparent coefficients of friction for seismic and aseismic slip are indistinguishable or zones with historically low rates of seismicity are prone to large earthquakes that have not been recorded.