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首页> 外文期刊>Geosphere >Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone
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Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone

机译：Cascadia俯冲区2000年梅吉坦克地震2000年的电影沿海沉降的最小地层证据

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摘要

Lithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out 0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record subsidence during megathrust earthquakes, mapping, qualitative diatom analysis, foraminiferal transfer function analysis, and 14 C dating of the contacts failed to confirm that any contacts formed through subsidence during great earthquakes. Based on the youngest peat-mud contact’s distinctness, 400 m distribution, ～0.6 m depth, and overlying probable tsunami deposit, we attribute it to the great 1700 CE Cascadia earthquake and(or) its accompanying tsunami. Minimal changes in diatom assemblages from below the contact to above its probable tsunami deposit suggest that the lower of several foraminiferal transfer function reconstructions of coseismic subsidence across the contact (0.1–0.5 m) is most accurate. The more limited stratigraphic extent and minimal changes in lithology, foraminifera, and(or) diatom assemblages across the other 11 peat-mud contacts are insufficient to distinguish them from contacts formed through small, gradual, or localized changes in tide levels during river floods, storm surges, and gradual sea-level rise. Although no data preclude any contacts from being synchronous with a megathrust earthquake, the evidence is equally consistent with all contacts recording relative sea-level changes below the ～0.5 m detection threshold for distinguishing coseismic from nonseismic changes.
机译：俄勒冈州中部河口沼泽下面的岩石学和微量碎屑生物物理学模型在连续地震期间Cascadia Megathrust破裂的地球物理模型通过统治＆ 2000年过去的0.5米的Coseismic沿海沉降。虽然核和露头中的地层包括多达12个泥浆泥浆触点，但与常规推断出在Megathrust地震中记录沉降的那些，映射，定性硅藻分析，传染率传递函数分析和14℃的触点约会未能确认在大地震期间通过沉降形成的任何接触。根据最小的泥炭泥接触的明显，＆ 400米分布，〜0.6米深度和覆盖的可能的海啸存款，我们将其归结为伟大的1700 CE Cascadia地震和（或）伴随的海啸。硅藻组合的最小变化从以下接触到上述可能的海啸沉积物表明，几个多氨基因素传递函数重建的近似接触（0.1-0.5米）的电影性沉降函数重建最准确。在其他11个泥炭泥缝触点上的岩性地点和（或）岩性组合的硅藻和（或）硅藻序列的最小变化越多，不足以将它们与通过河洪水洪水的潮汐水平的小，逐渐或局部变化的接触区分开，风暴潮，逐渐海平面上升。尽管没有数据妨碍与巨大地震同步的任何触点，但是证据同样一致地与录制相对海平面变化的所有接触，以区分从非肌炎的变化。

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