Currents, drag, and sediment transport induced by a tsunami
Currents, drag, and sediment transport induced by a tsunami
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海啸引起的海流、阻力和沉积物输送
DOI：
10.1029/2012jc007954
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发表时间：
2012
影响因子：
--
通讯作者：
D. Buscombe
中科院分区：
文献类型：
--
作者：
J. Lacy;D. Rubin;D. Buscombe
[1]我们报告的观测水面高程，电流，悬浮泥沙浓度（SSC）从一个10米深的网站在北方蒙特雷湾的内大陆架在2010年智利海啸的到来。速度分布测量从3.5米以上的床（单抗）的表面在2分钟的时间间隔，并从0.1至0.7单抗在1赫兹。从近床剖面仪的声学后向散射确定SSC。最初的海啸波指向海岸，周期约为16 min。最大波高为1.1 m，最大流速为0.36 m/s。在最强的冲击，近床速度明显受到摩擦和对数边界层的发展，延伸超过0.3 MAB的影响。我们估计摩擦速度和床面剪应力的对数剖面。对数结构表明，在这些时候，流动可以被表征为准稳定的。在海啸波的其他阶段，加速度项的大小在近床动量方程中很重要，表明不稳定流。海啸引起的最大床面剪应力（0.4 N/m2）超过了海底中粒砂的临界剪应力。海啸增强了海岸沉积物通量。水面高度和水流的振荡持续了几天。振荡主要由共振频率，其中最具活力的是蒙特雷湾的基本纵向频率。在18个月的观测中，最大流速（小时时间尺度）出现在海啸到达后4小时。
[1] We report observations of water surface elevation, currents, and suspended sediment concentration (SSC) from a 10-m deep site on the inner shelf in northern Monterey Bay during the arrival of the 2010 Chile tsunami. Velocity profiles were measured from 3.5 m above the bed (mab) to the surface at 2 min intervals, and from 0.1 to 0.7 mab at 1 Hz. SSC was determined from the acoustic backscatter of the near-bed profiler. The initial tsunami waves were directed cross shore and had a period of approximately 16 min. Maximum wave height was 1.1 m, and maximum current speed was 0.36 m/s. During the strongest onrush, near-bed velocities were clearly influenced by friction and a logarithmic boundary layer developed, extending more than 0.3 mab. We estimated friction velocity and bed shear stress from the logarithmic profiles. The logarithmic structure indicates that the flow can be characterized as quasi-steady at these times. At other phases of the tsunami waves, the magnitude of the acceleration term was significant in the near-bed momentum equation, indicating unsteady flow. The maximum tsunami-induced bed shear stress (0.4 N/m2) exceeded the critical shear stress for the medium-grained sand on the seafloor. Cross-shore sediment flux was enhanced by the tsunami. Oscillations of water surface elevation and currents continued for several days. The oscillations were dominated by resonant frequencies, the most energetic of which was the fundamental longitudinal frequency of Monterey Bay. The maximum current speed (hourly-timescale) in 18 months of observations occurred four hours after the tsunami arrived.