Induced stresses and fault potential in eastern Canada due to a realistic load: a preliminary analysis
Induced stresses and fault potential in eastern Canada due to a realistic load: a preliminary analysis
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加拿大东部由于实际载荷而产生的诱发应力和断层潜力：初步分析
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
H. Hasegawa
中科院分区：
文献类型：
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作者：
P. Wu;H. Hasegawa
为了理解冰后期回弹与地震之间的因果关系，使用一个简单的圆盘载荷模型：（1）计算冰川加载、融化和冰后期回弹在岩石圈和地幔中引起的应力;（2）评估冰川加载/回弹对上地壳地震破坏潜力的影响。的摩擦系数，环境构造应力的大小/方向，由于上覆岩石的应力，和岩石圈厚度的故障的潜在和实际模式的依赖性进行了研究。本文的突出特点是包括：（1）粘弹性地幔和应力迁移;（2）环境构造应力和上覆岩层应力在总应力场计算中的贡献。假设在整个地球上，有最佳取向的预先存在的虚拟故障，最初接近但不是在故障，因此，一个依赖于时间的量称为dFSM（相关的库仑-莫尔故障准则）可以定义为dFSM的负值将提倡断层或地震活动，而dFSM的正值将促进稳定性。结果表明，在构造应力大小和上覆应力的所有组合下，地壳载荷促进了载荷正下方断层的稳定性。在移除载荷时，如果由覆盖层引起的水平应力（Si）大于或等于覆盖层应力（121）的垂直分量（Si），则预测冰缘内的逆冲断层，其中（= SSi）。在这种情况下，理论预测断层或地震活动应该在冰川消退后立即达到最大值。如果上覆岩层引起的水平应力小于上覆岩层应力的垂直分量（1 < l），则理论预测冰缘内的断层稳定性。该理论预测了冰缘北部和南部的断层不稳定性。然而，破坏模式完全由i的值决定。本文还研究了构造应力大小与上覆岩层应力参数（1）之间的权衡关系。结果表明，较大的构造应力值可以用来补偿较小的1。分析结果表明，摩擦系数、岩石圈厚度和上地壳下的韧性带的变化对上述结论没有显著影响。
SUMMARY In order to understand the causal relation between postglacial rebound and earthquakes, a simple disc load model is used to: (1) calculate stresses induced in the lithosphere and mantle by glacial loading, melting and postglacial rebound; and (2) evaluate the effect of glacial loading/rebound on the failure potential for earthquakes in the upper crust. The dependence of the failure potential and the actual mode of failure on the coefficient of friction, the ambient tectonic stress magnitude/direction, the stress due to the overlying rocks, and lithospheric thickness are investigated. Prominent features of this paper are the inclusion of: (1) a viscoelastic mantle and thus the migration of stress; and (2) the ambient tectonic stress and overburden stress contributions in the calculation of the total stress field. It is assumed that, throughout the Earth, there are optimally oriented pre-existing virtual faults that are initially close to but not at failure; thus, a time-dependent quantity called dFSM (related to the Coulomb-Mohr failure criterion) can be defined such that a negative value of dFSM would advocate faulting or earthquake activities whereas a positive value of dFSM would promote stability. The results indicate that, under all combinations of tectonic stress magnitude and overburden stress, crustal loading promotes fault stability directly underneath the load. Upon the removal of the load, thrust faulting is predicted within the ice margin if the horizontal stress (S,) induced by the overburden is greater than or equal to the vertical component (S,) of the overburden stress (121, where (=SJS,). Under this condition, theory predicts that faulting or earthquake activity should have reached a maximum immediately after deglaciation. If the horizontal stress induced by the overburden is less than the vertical component of the overburden stress (1 < l), then theory predicts fault stability within the ice margin. The theory predicts fault instability both north and south of the ice margin. The mode of failure, however, is completely determined by the value of i. The trade-off between the tectonic stress magnitude and the overburden stress parameter (1) is also investigated. It is shown that a larger tectonic stress magnitude can be used to compensate a smaller value of 1. The results of this analysis show that variations in the coefficient of friction, lithospheric thickness and a ductile zone below the upper crust do not significantly affect the above conclusions.