Late Quaternary Crustal Deformation Along the Cascadia Subduction Zone in Southern and Central Coastal Oregon

研究目标如下：(1)绘制至少存在4个阶地的4个野外区域的海洋阶地图；(2)通过收集阶地沉积物中的可测年资料，建立阶地的数字年龄；(3)研究海洋阶地上的土壤发育，以确定土壤时间序列和土壤时间功能，根据土壤发育对梯田进行对比，并研究计算机模拟模型对海洋梯田进行数值年龄分配的能力；(4)将研究地点之间的梯田进行对比；以及(5)分析晚第四纪的变形。最后一个目标是汇编不同地点的绝对形变量，汇编抬升、倾斜和断层滑动速率，并确定沿海岸将变形划分为构造域的程度。我们预计，我们将成功地为每个研究地点的至少一个或两个较低的梯田分配数字年龄。如果土壤发育模拟模型是可行的，那么所有梯田的数值年龄都是可能的。到目前为止的地图(如下所述)表明，俄勒冈州南部海岸的变形在空间或时间上并不均匀，而是海岸被分割成宽阔的翘曲。断层与这些宽阔的翘曲有关，其中一些断层似乎是构造段的边界。因此，我们还预计，我们将能够识别具有不同海岸线长度、面积和变形速率(或速率范围)的构造段。区段的长度和这些区段内的相对变形年龄都应作为识别具有不同特征的俯冲构造响应的海岸区段的基础。

Research objectives are the following: (1) to map marine terraces in four field areas where at least four flights of marine terraces are present; (2) to establish numerical ages of terraces through collection of datable material form terrace deposits; (3) to study soil development on marine terraces for identifying soil chronosequences and soil chronofunctions, correlating terraces based on soil development, and investigating capabilities of a computer-simulation model for assigning numerical ages to marine terraces; (4) to correlate terraces among study sites; and (5) to analyze late Quaternary deformation. The last objective entails compilation of absolute magnitudes of deformation at the different sites, compilation of uplift, tilt and fault-slip rates, and determination of the extent to which deformation is segmented into structural domains along the coast. We anticipate that we will be successful in assigning numerical ages to at least the lower one or two terraces at each study site. If the soil development simulation model is feasible, then numerical ages of all terraces are a possibility. Mapping to date (described below) demonstrates that deformation along the southern coast of Oregon is not uniform in space or in time, but rather the coast is segmented into broad warps. Faults are associated with these broad warps, and some of these faults appear to be boundaries of structural segments. Therefore, we also anticipate that we will be able to identify tectonic segments that have different coastline lengths, areas, and deformation rates (or ranges of rates). Both the lengths of segments and the relative ages of deformation within these segments should serve as a basis for identifying segments of the coast with different characteristic tectonic responses to subduction.