Inverse modeling of velocities and inferred cause of overwash that emplaced inland fields of boulders at Anegada, British Virgin Islands
Inverse modeling of velocities and inferred cause of overwash that emplaced inland fields of boulders at Anegada, British Virgin Islands
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英属维尔京群岛阿内加达内陆巨石场的速度逆向建模和推断的过度冲刷原因
DOI：
10.1007/s11069-011-9725-8
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
S. Watt
中科院分区：
文献类型：
--
作者：
M. Buckley;Yong Wei;B. Jaffe;S. Watt
几个世纪前，数值水动力学模型、大碎屑逆沉积物输运模型和广泛的现场测量相结合，被用来区分海啸和袭击英属维尔京群岛阿内加达的风暴。总共测量了161块鹅卵石和巨石，重量从1.5到830公斤不等，距离海岸线1公里，距离边缘珊瑚礁顶部2公里。搬运的碎屑由低孔隙度的石灰岩组成，来自阿内加达低洼内部的露头。使用一个简单的泥沙输送模型计算了输送观测到的巨石所需的近床面流速的估计值，该模型考虑了流体对巨石的阻力、惯性、浮力和升力，并包括滑动和倾覆输送机制。利用线性涡动粘性模型将估计的近床面流速转换为深度平均流速，并将其与高分辨率海岸淹没模型的水位和深度平均流速时间序列进行比较。海岸淹没模型模拟了风暴潮和里斯本9.0级地震以及沿北美加勒比板块边界的两次假想地震引发的5级飓风和海啸的淹没。一个模拟的5级飓风和三个模拟的海啸都能够淹没巨石田并运输部分观察到的碎屑，但只有波多黎各海沟外隆起的正常断层上的8.0级地震能够在当前位置运送最大的碎屑。模型结果表明，虽然风暴波和海啸都能够产生必要的速度和时间加速度，以便在礁顶附近运送大块巨石，但波浪破碎和底部摩擦造成的波浪能量衰减限制了风暴波在内陆大距离运送大碎石的能力。通过敏感性分析，我们表明，即使使用泥沙输送模式中的系数，为巨石输送提供最低估计最小速度，来自5级飓风的风暴波也不能输送阿涅加达内部最大的巨石。由于建模方法中的不确定性，本文进行了广泛的灵敏度分析，并讨论了局限性。
A combination of numeric hydrodynamic models, a large-clast inverse sediment-transport model, and extensive field measurements were used to discriminate between a tsunami and a storm striking Anegada, BVI a few centuries ago. In total, 161 cobbles and boulders were measured ranging from 1.5 to 830 kg at distances of up to 1 km from the shoreline and 2 km from the crest of a fringing coral reef. Transported clasts are composed of low porosity limestone and were derived from outcrops in the low lying interior of Anegada. Estimates of the near-bed flow velocities required to transport the observed boulders were calculated using a simple sediment-transport model, which accounts for fluid drag, inertia, buoyancy, and lift forces on boulders and includes both sliding and overturning transport mechanisms. Estimated near-bed flow velocities are converted to depth-averaged velocities using a linear eddy viscosity model and compared with water level and depth-averaged velocity time series from high-resolution coastal inundation models. Coastal inundation models simulate overwash by the storm surge and waves of a category 5 hurricane and tsunamis from a Lisbon earthquake of M 9.0 and two hypothetical earthquakes along the North America Caribbean Plate boundary. A modeled category 5 hurricane and three simulated tsunamis were all capable of inundating the boulder fields and transporting a portion of the observed clasts, but only an earthquake of M 8.0 on a normal fault of the outer rise along the Puerto Rico Trench was found to be capable of transporting the largest clasts at their current locations. Model results show that while both storm waves and tsunamis are capable of generating velocities and temporal acceleration necessary to transport large boulders near the reef crest, attenuation of wave energy due to wave breaking and bottom friction limits the capacity of storm waves to transport large clast at great inland distances. Through sensitivity analysis, we show that even when using coefficients in the sediment-transport model which yield the lowest estimated minimum velocities for boulder transport, storm waves from a category 5 hurricane are not capable of transporting the largest boulders in the interior of Anegada. Because of the uncertainties in the modeling approach, extensive sensitivity analyses are included and limitations are discussed.
孔隙率在区分海啸和飓风巨石就位中的作用——加勒比南部小安的列斯群岛的案例研究
影响因子：
5.3
作者：
Spiske M;Böröcz;Bahlburg
通讯作者：
Bahlburg