Pacific Storms, EI Niño and Tsunamis: Competing Mechanisms for Sand Deposition in a Coastal Marsh, Euchre Creek, Oregon
Pacific Storms, EI Niño and Tsunamis: Competing Mechanisms for Sand Deposition in a Coastal Marsh, Euchre Creek, Oregon
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太平洋风暴、厄尔尼诺现象和海啸：俄勒冈州尤克溪沿海沼泽沙子沉积的竞争机制
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
E. Hemphill
中科院分区：
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作者：
R. Witter;H. Kelsey;E. Hemphill
在过去的600年里，4个良好的分选砂床，每个突然较低的接触，沉积在Euchre河沼泽风暴波和海啸。保存在沙子中的咸水海洋硅藻表明海洋起源，但砂床的非独特的物理特性，否则防止沉积机制的区别。然而，150年的平均复发间隔的砂床是显着小于500年至540年的卡斯卡迪亚俯冲带地震的推断复发间隔，这表明并非所有的砂床记录当地的海啸。我们认为风暴波在极端的海平面和远程海啸产生的其他地方在环太平洋地区，除了卡斯卡迪亚海啸，作为潜在的砂沉积机制在冲刷设置的俄勒冈州海岸。对验潮仪和气象浮标数据的震级-频率分析，沿着遥远海啸的历史记录，表明叠加在极端海平面上的风暴波上升达到的高度每10年大于5米，每世纪可能超过7米，而类似震级的遥远海啸在几百年内重复发生。最有可能成为与公元有关的海啸存款的。1700年卡斯卡迪亚地震是最厚的砂存款，由多个，罚款向上的床。其他的沙沉积物很可能记录了多次风暴波的冲刷，或者可能，但不太可能，一个遥远的海啸。一个简单的模型，相对海平面的地震周期的反应预测，较低的助跑海拔是必要的海洋淹没的沼泽在过去的600年中，由于同震沉降。
During the past 600 years, 4 well-sorted sand beds, each with abrupt lower contacts, were deposited in the Euchre Creek marsh by storm waves and a tsunami. Brackish-marine diatoms preserved within the sand indicate a marine origin, but nonunique physical characteristics of the sand beds otherwise prevent the distinction of the depositional mechanism. However, a 150 year average recurrence interval for the sand beds is significantly smaller than the 500 to 540 year inferred recurrence interval for Cascadia subduction zone earthquakes, indicating that not all of the sand beds record local tsunamis. We consider storm-wave runup during extreme ocean levels and remote tsunamis generated elsewhere in the Pacific Rim, in addition to Cascadia tsunamis, as potential sand depositional mechanisms in washover settings of the Oregon coast. Magnitude-frequency analyses of tide gage and weather buoy data, along with historic records of remote tsunamis, indicate that storm-wave runup superimposed on extreme ocean levels attain heights >5 m every 10 years and may exceed 7 m every century, whereas remote tsunamis of similar magnitudes recur over periods of several hundred years. The best candidate for a tsunami deposit associated with the A.D·. 1700 Cascadia earthquake is the thickest sand deposit which consists of multiple, fining-upward beds. The other sand deposits most likely record multiple episodes of storm-wave washover or possibly, but less likely, a remote tsunami. A simple model of relative sea-level response to the seismic cycle predicts that lower runup elevations were necessary for marine inundation of the marsh at times during the past 600 years due to coseismic subsidence.