Fault formation in porous sedimentary rocks at high strain rates: First results from the Upheaval Dome impact structure, Utah, USA
Fault formation in porous sedimentary rocks at high strain rates: First results from the Upheaval Dome impact structure, Utah, USA
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高应变率下多孔沉积岩的断层形成：来自美国犹他州剧变穹顶冲击结构的第一个结果
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发表时间：
2011
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影响因子：
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通讯作者：
Richard A. Schultz
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作者：
W. R. Key;W. R. Key;Richard A. Schultz
先前的理论工作表明，多孔沉积岩受到足够高的应变率可能不会形成变形带损伤区（DBDZs）。这一假设是通过检查断层内的多孔纳瓦霍砂岩在UppermandDome的影响结构，国家公园，东南部犹他州，在高应变率的条件是已知的发生。我们没有发现任何证据表明，在隆起穹丘的可接近断层面上沿着形成了DBDZ。相反，纳瓦霍砂岩中的一层粉碎的石英颗粒出现在断层面附近。在南加州圣安德烈亚斯断层沿着的结晶岩和沉积岩中，以及南非博斯曼断层沿着的变质岩中，也观察到了与动态破裂有关的类似物质。从Upperdance Dome收集的粉碎材料中获得的测量晶粒尺寸与应变速率为101 -3 × 10 3 s −1一致。沿着圣安德烈亚斯断层的粉状沉积岩意味着应变率为10 - 10 1 s-1。沿着隆起穹丘断层的应变率远高于与板内构造相关的平均值，但与沿着圣安德烈亚斯断层等断层的地震滑动率一致或更快。我们的研究结果支持了多孔岩石变形速率依赖性的假设。
Previous theoretical work has suggested that porous sedimentary rocks subjected to sufficiently high strain rates may not form deformation band damage zones (DBDZs). This hypothesis is evaluated by an examination of faults within the porous Navajo Sandstone at the Upheaval Dome impact structure in Canyonlands National Park, southeastern Utah, where high strain-rate conditions are known to have occurred. We found no evidence for DBDZ formation along the accessible fault planes at Upheaval Dome. Instead, a layer of pulverized quartz grains within the Navajo Sandstone occurs adjacent to the fault planes. Similar material has been observed in association with dynamic rupture in crystalline and sedimentary rocks along the San Andreas fault in southern California and in metamorphic rocks along the Bosman fault in South Africa. Measured grain sizes obtained from the pulverized material collected at Upheaval Dome are consistent with strain rates of ∼1–3 × 10 3 s −1 . Pulverized sedimentary rocks along the San Andreas fault imply strain rates of ∼10 −2 to 10 1 s −1 . Strain rates along the faults at Upheaval Dome are well above the average values associated with intraplate tectonics but are consistent with, or faster than, seismic slip rates along faults such as the San Andreas fault. Our results support the hypothesized rate dependence of deformation in porous rocks.