Seismic and aseismic slip pulses driven by thermal pressurization of pore fluid
Seismic and aseismic slip pulses driven by thermal pressurization of pore fluid
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孔隙流体热加压驱动的地震和抗震滑移脉冲
DOI：
10.1029/2011jb008889
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发表时间：
2012
影响因子：
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通讯作者：
D. Garagash
中科院分区：
文献类型：
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作者：
D. Garagash
[1]有几条证据表明，低渗透断层核内孔隙流体的热增压作用(TP)可能在地震滑动的发展中起关键作用。为了阐明Tp对自发性断层滑动的影响，我们考虑了具有恒定滑动摩擦的断层上稳定传播的滑动脉冲的解，其水平可能反映了破裂前沿的其他热激活过程(如对凹凸体的闪光加热)。当脉冲前沿到达时，在从锁定状态开始的滑移加速过程中，发生了基本上不排水的绝热TP，相应地，断层强度降低。随着时间的推移，剪切带加热速率的减小(断层强度的降低)和热液扩散速率的增加抵消了Tp，导致强度的部分恢复，滑移减速，并最终锁定和愈合滑移。结果表明，破裂速度vr随主剪切带厚度的增加而减小。对于实验室约束的断层泥参数，TP-PULSE解预测在毫米到厘米薄的主剪切带上的地震滑动(Vr∼Km/S)，以及在相对较厚的(h∼1 m)剪切带上的无地震滑动，其Vr Vr为10公里/天，滑动速率比板块速率高1-2个数量级。TP-PULSE模型的这些和其他预测分别与地壳和俯冲板块间大地震以及慢滑瞬变(北卡斯卡迪亚)的独立观测约束集一致。在热量和孔隙流体的扩散传输变得有效后不久锁定滑移，显着地将最大同震温升限制在远低于先前理论估计的值。因此，最近提出的解释强烈同震断层减弱的宏观熔融和一些热分解反应的开始，在地震孕育区的大部分地区被排除在外。
[1] There are several lines of evidence that suggest that thermal pressurization (TP) of pore fluid within a low-permeability fault core may play the key role in the development of earthquake slip. To elucidate effects of TP on spontaneous fault slip, we consider solutions for a steadily propagating slip pulse on a fault with a constant sliding friction, the level of which may reflect other thermally-activated processes at the rupture front (such as the flash heating on asperities). Upon arrival of the pulse front, essentially undrained-adiabatic TP takes place during the initial slip acceleration from the locked state with a corresponding reduction of the fault strength. With passage of time, the diminishing rate of heating (due to the reduced fault strength) and increasing rate of hydrothermal diffusion from the shear zone offset TP and result in partial recovery of the strength, slip deceleration and eventual locking and healing of the slip. We show that the rupture speedvr decreases with thickness hof the principal shear zone. For lab-constrained values of fault-gouge parameters, the TP-pulse solution predicts seismic (vr∼ km/s) slip on a millimeter-to-cm thin principal shear zone; and aseismic slip withvr ∼ 10 km/day and slip rates 1–2 orders above the plate rate on a relatively thick (h∼ 1 m) shear zone. These and other predictions of the TP-pulse model are consistent with the independent sets of observational constraints for large crustal and subduction interplate earthquakes, and slow slip transients (North Cascadia), respectively. Locking of the slip soon after the diffusive transport of the heat and pore fluid becomes efficient significantly limits the maximum co-seismic temperature rise to values well below previous theoretical estimates. As a result, the onset of macroscopic melting and some of thermal decomposition reactions, recently suggested to explain strong co-seismic fault weakening, are precluded over much of the seismogenic zone.