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DOI | 10.1016/j.tecto.2020.228550 |
On the rotation and frictional lock-up of normal faults: Explaining the dip distribution of normal fault earthquakes and resolving the low-angle normal fault paradox | |
Reston T. | |
发表日期 | 2020 |
ISSN | 00401951 |
卷号 | 790 |
英文摘要 | Classical rock mechanics predicts that normal faults should form at 60–65°, rotating to 30–40° before locking, so widespread slip at around 20° is considered paradoxical. Furthermore, the dip distribution of normal fault earthquakes has a distinct, unexplained peak at ~45°. For both problems, some combination of low friction, high fluid pressures, stress rotation and efficiency of low-angle slip have been suggested but provide at best a partial solution. A simple quantitative model for normal fault rotation (iterating between slip on faults and distributed strain) predicts that faults spend more time at lower angles. Combining this result with Mohr-Coulomb analysis of the range where seismogenic normal faults should lock up predicts the dip distribution of seismogenic normal faults and matches both the range and 45° peak observed for normal fault earthquakes. As even the lowest dips of normal fault ruptures fall within the limits of fault reactivation, slip on seismogenic low-angle normal faults is not paradoxical. A new Mohr-Griffith solution to the limits of fault reactivation extends the analysis into the top few km, where low-angle slip is best constrained by field observations, and shows that low cohesion normal faults can remain active at <20° without recourse to very low friction, high fluid pressures or stress rotation. This analysis thus resolves the long-standing paradox of slip on low-angle normal faults. Where continued rotation or changes in mechanical properties cause low-angle faults to lock in the shallow subsurface, a new fault propagates upward from the point of lock-up, transferring a hanging wall slice to the footwall, to be rafted up and out as a rider block. By recording the dip/depth of lock-up, riders atop detachments constrain the mechanics of faulting and of lock-up. © 2020 Elsevier B.V. |
关键词 | Detachment faultsEarthquakesNormal faultingRiftingRock mechanics |
英文关键词 | Earthquakes; Friction; Locks (fasteners); Rock mechanics; Rotation; Distributed strain; Fault reactivation; Field observations; Fluid pressures; Normal faults; Quantitative modeling; Shallow subsurface; Stress rotation; Fault slips; Coulomb criterion; earthquake mechanism; friction; mechanical property; Mohr theory; normal fault; rotation; rupture |
语种 | 英语 |
来源期刊 | Tectonophysics
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文献类型 | 期刊论文 |
条目标识符 | http://gcip.llas.ac.cn/handle/2XKMVOVA/207860 |
作者单位 | School of Geography, Earth and Environmental Sciences, University of Birmingham, United Kingdom |
推荐引用方式 GB/T 7714 | Reston T.. On the rotation and frictional lock-up of normal faults: Explaining the dip distribution of normal fault earthquakes and resolving the low-angle normal fault paradox[J],2020,790. |
APA | Reston T..(2020).On the rotation and frictional lock-up of normal faults: Explaining the dip distribution of normal fault earthquakes and resolving the low-angle normal fault paradox.Tectonophysics,790. |
MLA | Reston T.."On the rotation and frictional lock-up of normal faults: Explaining the dip distribution of normal fault earthquakes and resolving the low-angle normal fault paradox".Tectonophysics 790(2020). |
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