Implications of fault-valve behaviour for rupture nucleation and recurrence
Implications of fault-valve behaviour for rupture nucleation and recurrence
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DOI：
10.1016/0040-1951(92)90065-e
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发表时间：
1992-09
期刊：
影响因子：
2.9
通讯作者：
R. Sibson
中科院分区：
文献类型：
--
作者：
R. Sibson
Sibson，R.H.，1992.断裂成核和再发的断层阀行为的意义。In：T. Mikumo，K.阿基，M. Ohnaka，L. J. Ruff和P. K. P. Spudich（编辑），震源物理学和地震前兆。构造物理学，211：283- 293。在简单的递归模型中，假设当构造剪应力（τ）上升到某个恒定的临界水平时，此类断层发生破坏。然而，摩擦强度（τf）也可能在地震间隔期内发生显著变化，在这种情况下，连续地震之间的复发间隔与τ f和τ的时间依赖性有关。τ f随τ变化的方式部分取决于断层上正应力和剪应力的耦合，并与断层活动方式和断层加载方式有关。内聚强度和静摩擦力的时间依赖性也可能起作用。然而，流体压力循环的结果ofault-valvepearance（断层横切流体压力的超流体静力梯度）可能会引起非常大的变化，断层强度。地质证据表明，在孕震区的较低区域，价值作用可能特别重要，在那里，大的破裂往往会成核，最大的流体压力波动与断层有关，这些断层由于流体超压而仍然活跃，尽管在当时的应力场中重新激活的方向严重错误。在此类断层附近，可能会出现大范围的水力压裂破坏。由于断层阀活动（Δτf）引起的地震间摩擦强度的变化可能大大超过破坏时的剪应力下降（典型情况下，1 <Δτ< 10 MPa）。在这种情况下，连续事件之间的复发间隔可能是高度可变的。根据Δτ f和Δτ的相对大小，以及剪应力积累和地震间流体压力水平变化之间的耦合，可能会出现各种各样的复发行为。
Sibson, R.H., 1992. Implications of fault-valve behaviour for rupture nucleation and recurrence. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors.Tectonophyslcs, 211: 283–293.Earthquakes in the shallow crust are generally thought to arise from the frictional instability of existing faults under shear stress. In simple recurrence models, failure on such faults is assumed to occur when tectonic shear stress (τ) rises to some constant critical level. However, frictional strength (τf) may also vary substantially through the interseismic period, in which case recurrence intervals between successive earthquakes are related to the time-dependence of τfas well as τ . In part, the manner in which τfchanges with τ depends on the coupling between normal stress and shear stress on the fault, and is related to the mode of faulting and the manner of fault loading. Time-dependence of cohesive strength and static friction may also play a role. However, fluid pressure cycling as a consequence offault-valvebehaviour (where the fault transects a suprahydrostatic gradient in fluid pressure) may give rise to very large variations in fault strength. Geological evidence suggests thatvalue-action may be especially important in the lower regions of the seismogenic zone, where large ruptures tend to nucleate, the largest fluid pressure fluctuations being associated with faults that remain active as a consequence of fluid overpressure though severely misoriented for reactivation in the prevailing stress field. Extensive hydrofracture dilatancy is likely to develop prefailure in the vicinity of such faults. Changes in frictional strength over the interseismic period as a result of fault-valve activity (Δτf) may greatly exceed the shear stress drop at failure (1 <Δτ< 10 MPa, typically). In such circumstances, recurrence intervals between successive events can be highly variable. A rich variety of recurrence behaviour becomes possible, depending on the relative magnitudes of Δτfand Δτ, and the coupling between shear stress accumulation and changing fluid pressure levels through the interseismic period.