Geodetic Constraints on Arc Dynamics and Coupling on the Plate Interface in the Lesser Antilles

小安的列斯群岛弧动力学和板块界面耦合的大地测量约束

• 批准号: 1063246
• 负责人: Glen Mattioli
• 金额: $ 3万
• 依托单位: University of Texas at Arlington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1063246&HistoricalAwards=false
• 关键词: Geodetic; Constraints; Arc; Dynamics; Coupling

PROJECT SUMMARYAlong obliquely convergent plate boundaries, the relative plate motion vector frequently is partitioned into arc-normal and arc-parallel components. Complete separation of the normal and parallel components leads to arc-parallel thrusts and folds in the forearc and arc-parallel strike-slip faults in the volcanic arc. The forearc thus translates relative to the interior of the overriding plate. Partial separation of the two components, however, is more common, particularly when coupling occurs across the plate interface. In addition, changes in obliquity of convergence along the plate boundary can create arc- parallel gradients in shear stress to produce internal deformation of the forearc. Either arc-parallel extension or compression may occur. The northeastern Caribbean corner affords an excellent opportunity to use Global Positioning System (GPS) geodesy to examine strain partitioning, coupling along the plate interface, and arc-parallel extension in a slow subduction zone. Caribbean-North American relative plate motion is ~20 mm/yr. Thetrend of the plate boundary changes from NNW in the Lesser Antilles to EW along the eastern Greater Antilles. The ENE azimuth of the convergence vector predicts near normal subduction at Martinique and near strike-slip motion at Puerto Rico. Horizontal slip directions derived from shallow-thrust earthquakes east of the Lesser Antilles lie between the predicted convergence direction and the normal to the subduction trace, suggesting that some partitioning occurs. The focus is on the northern Lesser Antilles for four reasons. First, The PI's have collected GPS data in the region since 1994 and have developed a Caribbean reference frame. Second, GPS-derived velocities for the southern Lesser Antilles agree within error with those predicted for Caribbean motion relative to North America at those locations, implying little or no deformation of the overriding plate. In contrast, a simple elastic half-space model shows that preliminary GPS geodetic results from the northern Lesser Antilles are consistent with coupling along the plate interface. Third, the northern Lesser Antilles arc consists of two concentric island chains that provide subaerial exposure closer to the trench and over a greater arc transverse distance than do the islands in the south. Fourth, NE-trending structures transverse to the arc in the northern Lesser Antilles accommodate a component of arc-parallel extension. In addition, volcanic centers on individual islands have migrated parallel to the arc at rates equivalent to those of the arc-parallel component of convergence. Finally, EW-oriented extension along NS-trending structures has been measured by GPS geodesy for the EW-trending eastern Greater Antilles. The slow relative plate motion in the northeastern Caribbean requires long GPS time-series to yield robust velocities to assess potential arc-parallel strain gradients. This five-year proposal, therefore, builds on data collected in the northeastern Caribbean since 1994.If no motion of the islands of the northern Lesser Antilles relative to the Caribbean plate can be detected over temporal scales of a decade or longer a scenario that is unlikely given our preliminary dataset these sites will be used to provide additional constraints for the Caribbean reference frame formulation. The proposed work includes: collection and processing of GPS data; noise analysis, which is particularly important where motion is slow such as the Caribbean; and modeling of results. The questions to be addressed are: Is oblique slip partitioned into trench parallel and normal components in slow subduction zones, i.e. the northern Lesser Antilles? If partitioning occurs, does it depend upon obliquity of convergence? What is the degree of coupling along the plate interface in the northern Lesser Antilles? Is arc-parallel extension of sufficient magnitude for detection by GPS geodesy? If so, does it increase in magnitude as obliquity of subduction increases? Are the rates of arc-parallel slip and/or arc-parallel extension consistent with rates of migration of volcanic centers within the northern Lesser Antilles? What are the implications of this for the dynamics of deep magmatic processes? Determining whether the leading edge of the Caribbean plate corner in the eastern Greater Antilles and the Lesser Antilles is composed of distinct block(s)that move relative to the Caribbean interior also will constrain seismic hazard in the northeastern Caribbean, an area that is little studied and particularly at risk for seismogenic tsunamis.

项目摘要倾斜地收敛板边界，相对板运动矢量经常被分配为弧 - 正常和ARC平行分量。 正常和并行组件的完全分离会导致弧线和平行的弧线 - 平行滑移断层在火山弧中的弧线和折叠。 因此，前臂相对于覆盖板的内部翻译。 但是，这两个组件的部分分离更为常见，尤其是当耦合在整个板界面上发生耦合时。 此外，沿板边界的倾斜斜率变化可以在剪切应力下产生弧形梯度以产生前臂的内部变形。 可能会发生电弧并行延伸或压缩。加勒比东北角为使用全球定位系统（GPS）测量系统提供了一个绝佳的机会来检查劳动分区，沿板界面沿板界面耦合以及在慢速俯冲带中的ARC平行延伸。 加勒比 - 北美相对板运动为约20毫米/年。 板边界的thetend从较小的安特列斯群岛中的nnw变成了沿东部巨人的EW。 收敛载体的ENE方位角预测马提尼克岛的正常俯冲和波多黎各的走滑运动几乎正常。 从较小的安特列斯（Bimess Antilles）以东的浅色地震衍生出的水平滑动方向位于预测的融合方向和俯冲痕迹正常之间，这表明发生了某些分区。 重点是北部小群岛，原因有四个。 首先，自1994年以来，PI已收集了该地区的GPS数据，并开发了加勒比海参考框架。 其次，南部小安特列斯群岛的GPS衍生的速度与在这些位置相对于北美的加勒比运动预测的速度一致，这意味着覆盖板的变形很小或没有变形。 相比之下，一个简单的弹性半空间模型表明，北部较小的安特列斯群岛的初步GPS大地测量结果与沿板界面的耦合一致。 第三，北部较小的安特列斯（Antilles Arc）由两个同心岛链组成，这些岛链与南部的岛屿相比，可提供接近沟槽和更大的弧形横向距离。 第四，NE趋势结构横向在北部小安提斯（Antelles）横向弧形结构可容纳ARC平行延伸的组成部分。此外，各个岛屿上的火山中心以与收敛的弧线平行成分相等的速率平行于弧线迁移。 最后，通过GPS GEODESY测量了EW趋势的东部大型安特列斯，已经测量了沿NS趋势结构的EW面向延伸。加勒比东北部的慢速相对板运动需要长的GPS时间序列才能产生稳健的速度，以评估潜在的ARC平行应变梯度。 因此，这项为期五年的提案以自1994年以来在加勒比东北部收集的数据为基础。鉴于我们的初步数据集，这些站点将用于为加勒比海参考框架公式提供其他约束。 拟议的工作包括：收集和处理GPS数据；噪声分析，这在运动缓慢（例如加勒比海）的情况下尤其重要；和结果的建模。 要解决的问题是：在慢速俯冲带（即北部较小的安特列斯）中，是否将倾斜滑动分区和正常组件分为平行和正常的组件？如果发生分区，是否取决于收敛的倾斜度？沿北部小all的板界面沿板界面的耦合程度是多少？ GPS GEODESY检测到足够幅度的弧线平行扩展吗？如果是这样，随着俯冲倾斜的增加，它会增加幅度吗？ ARC平行滑移和/或ARC平行延伸的速率是否与北部小针鸟群体内火山中心的迁移率一致？ 这对深层岩浆过程的动态有何影响？ 确定东部大安特列斯群岛和较小的安特列斯的加勒比海板角的前缘是否由与加勒比内部相对于加勒比海内部移动的独特块组成，也将限制加勒比东北部的地震危险特别是有危险的海啸海啸的风险。