Injection-induced seismicity on basement faults including poroelastic stressing
Injection-induced seismicity on basement faults including poroelastic stressing
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DOI：
10.1002/2015jb012561
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发表时间：
2016-04-01
影响因子：
3.9
通讯作者：
Segall, P.
中科院分区：
文献类型：
--
作者：
Chang, K. W.;Segall, P.
大多数重要的诱发地震发生在沉积盖层之下的基底内的断层上。在这个二维平面应变数值研究中，我们研究了基底断层对流体注入上覆地层的完全孔隙弹性响应，同时考虑了（1）断层带的渗透性和（2）断层与目标层的水力连通性。给定水力和力学性质，我们计算库仑应力的时空变化，我们将其分离为（1）孔隙弹性应力的变化Δ τ（s）+ f Δ sigma（n），其中Δ τ（s）和Δ sigma（n）是剪切应力和法向应力的变化（Delta tau（s）> 0和Delta sigma（n）0都有利于滑动），以及（2）孔隙压力f的变化Delta p。孔隙压力扩散到水力连通的渗透性断层中主导其机械稳定性。然而，对于水力隔离或低渗透性断层，即使没有升高的孔隙压力，传递到更深的基底水平的孔隙弹性应力也会触发滑动。用迪特里希（1994）的模型预测了基底断裂带的地震活动率。由于孔隙压力的直接扩散，高地震活动率可能发生在渗透性的水力连接断层上。较低的利率预测孤立的陡倾角的正断层，造成完全由孔隙弹性应力。相反，地震活动相似的方向逆断层被抑制。
Most significant induced earthquakes occur on faults within the basement beneath sedimentary cover. In this two-dimensional plane strain numerical study, we examine the full poroelastic response of basement faults to fluid injection into overlying strata, considering both (1) the permeability of the fault zone and (2) the hydraulic connectivity of the faults to the target horizon. Given hydraulic and mechanical properties, we compute the spatiotemporal change in Coulomb stress, which we separate into (1) the change in poroelastic stresses Delta tau(s) + f Delta sigma(n),where Delta tau(s) and Delta sigma(n) are changes in shear and normal stress (Delta tau(s)> 0 and Delta sigma(n) 0 both favor slip), and (2) the change in pore pressure f Delta p. Pore pressure diffusion into hydraulically connected, permeable faults dominates their mechanical stability. For hydraulically isolated or low-permeability faults, however, poroelastic stresses transmitted to deeper basement levels can trigger slip, even without elevated pore pressure. The seismicity rate on basement fault zones is predicted using the model of Dieterich (1994). High seismicity rates can occur on permeable, hydraulically connected faults due to direct pore pressure diffusion. Lower rates are predicted on isolated steeply dipping normal faults, caused solely by poroelastic stressing. In contrast, seismicity on similarly oriented reverse faults is inhibited.