Rupture area and displacement of past Cascadia great earthquakes from coastal coseismic subsidence
Rupture area and displacement of past Cascadia great earthquakes from coastal coseismic subsidence
复制标题
历次卡斯卡迪亚大地震沿海同震沉降造成的破裂面积和位移
DOI：
10.1130/b30108.1
复制
发表时间：
2010
影响因子：
4.9
通讯作者：
R. Hyndman
中科院分区：
文献类型：
--
作者：
L. Leonard;C. Currie;S. Mazzotti;R. Hyndman
沿海沼泽记录了卡斯卡迪亚俯冲带大地震同震位移的6500年历史。我们根据与巨型逆冲断层触发的浊积岩的相关性，编制了过去巨型逆冲断层事件的同震位移估计值，并根据沼泽位移与位错模型预测的比较，估计了巨型逆冲断层滑动。沼泽地相关资料与已发表的浊流记录所定义的事件破裂范围一致，平均复发间隔为6500年，向北从~230年增加到~480年。在Marsh数据的约束下，同震破裂带的宽度与由大地测量和热测量数据推断的震间闭锁带的下倾宽度基本一致。在最南端的卡斯卡迪亚，该模型不包括门多西诺三重连接点附近的复杂变形，海岸数据可能更好地拟合一个模型，比从区域地球物理数据推断的破裂窄约25%。在每个沿海沼泽地，同震位移大致相似，从事件到事件，独立的时间，因为前一个事件。公元1700年地震的滑动与之前的应变积累间隔（~200年）一致，仅在边缘的北方和南端，但在华盛顿州南部和北方俄勒冈州，它显然要高得多，可能表明震后污染和/或追赶同震滑动，以弥补前一事件的缺陷。位错模型和沼泽数据之间的整体协议的大部分利润意味着这种模式可以有效地应用于破裂和地面震动的预测。
Coastal marshes record a 6500 yr history of coseismic displacements in great earthquakes at the Cascadia subduction zone. We compiled estimates of coseismic displacement for past megathrust events based on correlations with megathrust-triggered turbidites, and estimated megathrust slip based on comparisons of marsh displacements with dislocation model predictions. Age-correlated marsh data are compatible with event rupture extents defi ned by the published turbidite record , and a 6500 yr mean recurrence interval that increases northward from ~230 to ~480 yr. Within the constraints of the marsh data, the width of the coseismic rupture zone generally agrees with the downdip width of the interseismic locked zone inferred from geodetic and thermal data. In southernmost Cascadia, where the model does not include the complex deformation near the Mendocino triple junction, the coastal data may be better fi t by a model with an ~25% narrower rupture than that inferred from regional geophysical data. At each coastal marsh site, coseismic displacements are roughly similar from event to event, independent of the time since the previous event. Slip in the A.D. 1700 earthquake was consistent with the preceding interval of strain accumulation (~200 yr) only at the northern and southern ends of the margin, but it was apparently much higher in southern Washington and northern Oregon, possibly indicating postseismic contamination and/or catch-up coseismic slip to make up for a defi cit in the preceding event. Overall agreement between the dislocation models and the marsh data for most of the margin implies that such models can be usefully applied to rupture and ground shaking predictions.