EARTHQUAKE NUCLEATION ON FAULTS WITH RATE-DEPENDENT AND STATE-DEPENDENT STRENGTH
EARTHQUAKE NUCLEATION ON FAULTS WITH RATE-DEPENDENT AND STATE-DEPENDENT STRENGTH
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DOI：
10.1016/0040-1951(92)90055-b
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发表时间：
1992-09-30
期刊：
影响因子：
2.9
通讯作者：
DIETERICH, JH
中科院分区：
文献类型：
--
作者：
DIETERICH, JH
具有速率和状态相关的本构性质的断层再现了一系列观察到的断层滑动现象，包括在高于某些临界应力水平的应力下滑动不稳定的自发成核和滑动不稳定后强度的恢复。用具有空间变化性质的平面应变断层模型计算表明，加速滑移先于失稳，并局限于一个断层斑块。对于不稳定的断层滑动，断层块的尺寸遵循最小临界长度的标度关系。临界长度是正应力、加载条件和本构参数（包括D(c)、特征滑移距离）的函数。如果滑移发生在超过临界尺寸的斑块上，则随着不稳定时间的临近，快速加速区的长度倾向于收缩到特征尺寸。得到了一个均匀的固定补丁模型的解，它与平面应变模型的结果很好地吻合。在很大范围的条件下，在稳态应力以上，随着初始应力的增加，不稳定时间的对数线性减小。由于成核斑块长度和前兆位移与D(c)成正比，前兆滑移力矩以D(c)3表示。D(c)的比例目前是一个悬而未决的问题。除非地震断层的D(c)明显大于实验室断层的观测值，否则地震成核过程产生的前兆应变可能太小，无法用现有的观测方法检测到。排除成核带的D(c)控制后续地震震级的可能性，那么一个地区最小地震的震源尺寸为成核斑块的大小提供了上限。
Faults with rate- and state-dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability. Calculations with a plane-strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch. The dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip. The critical length is a function of normal stress, loading conditions and constitutive parameters which include D(c), the characteristic slip distance. If slip starts on a patch that exceeds the critical size, the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches. Solutions have been obtained for a uniform, fixed-patch model that are in good agreement with results from the plane-strain model. Over a wide range of conditions, above the steady-state stress, the logarithm of the time to instability linearly decreases as the initial stress increases. Because nucleation patch length and premonitory displacement are proportional to D(c), the moment of premonitory slip scales by D(c)3. The scaling of D(c) is currently an open question. Unless D(c) for earthquake faults is significantly greater than that observed on laboratory faults, premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods. Excluding the possibility that D(c) in the nucleation zone controls the magnitude of the subsequent earthquake, then the source dimensions of the smallest earthquakes in a region provide an upper limit for the size of the nucleation patch.