Kilometer-Scale Fault Zone Structure and Kinematics Along the San Andreas Fault near Parkfield, California

由于城市不断向地震多发区发展，地震对全球社会的威胁越来越大，但我们对地震行为的了解有限。对断层的基本了解需要详细描述岩体和构造的几何形状及其在断层带内和邻近断层带的运动。该项目为中南部圣安德烈亚斯断层的大量仪器和层析成像的帕克菲尔德部分提供了这样的解释，定义了圣安德烈亚斯断层沿着主要岩体的位置、姿态和特征，并确定了与断层带主要结构相关的活动变形速率。California.by详细的地质和地貌数据集和几何和运动学模型是有价值的解决有关景观发展沿着走滑断层带，在走滑断层带内和邻近的上地壳块体的运动，并在这一重要的断层带内和邻近的地质历史所定义的材料属性的问题。此外，这些数据和推论对于全面了解EarthScope要素：圣安德烈亚斯断层深度观测台的结果至关重要，目前正在对圣安德烈亚斯断层深度观测台半径10公里以内的地区进行地质和地貌测绘（比例尺为1：6000或更大）。在一个较低的，但仍然相对详细的比例尺（1：24000或更大），帕克菲尔德地区的选定部分正在映射，以提高解释的结构地质，地貌和地质年代学数据。通过对第三系沉积岩和花岗质岩石样品的磷灰石裂变径迹研究，可以推断该区的折返和岩石隆升历史。地貌分析有助于记录该地区活动地质结构的几何形状和速率，包括主要的圣安德烈亚斯断层，附属的走滑断层，以及附近的倾滑断层和褶皱。这种结构可以通过它们对地貌和年轻矿床的破坏来识别，它们的几何形状可以通过解释与它们相关的变形的区域分布来推断。这些调查包括建立该地区主要水系的阶地年代序列，确定活动构造沿着的变形速率，以及改善古地震记录。与山崩有关的迁移率正在与根据磷灰石裂变径迹热年代学推断的同一区块的剥露率进行比较。地质和地貌绘图结果和遥感图像将编入数字地理空间数据系统。

Earthquakes are an increasing threat to societies globally because of continued urban development into earthquake-prone areas, yet our understanding of earthquake behavior is limited. Fundamental understanding of faulting requires detailed description of the geometry of rock bodies and structures and their motions within and adjacent to fault zones. This project is providing such an explanation for the heavily instrumented and geophysically-imaged Parkfield section of the San Andreas Fault in south-central California.by defining the positions, attitudes, and characteristics of the major rock bodies along the San Andreas Fault, and determining the rates of active deformation associated with the principal structures of the fault zone. The detailed geologic and geomorphic data sets and geometric and kinematic models are valuable for addressing questions related to landscape development along strike-slip fault zones, the motions of blocks in the upper crust within and adjacent to strike-slip fault zones, and the material properties as defined by geologic history within and adjacent to this important fault zone. In addition, the data and inferences are essential for a complete understanding of the results from the EarthScope element: San Andreas Fault Observatory at Depth (SAFOD).Geologic and geomorphic mapping (1:6000 scale or greater) in an area within a 10 km radius of SAFOD is being performed. At a lower but still relatively detailed scale (1:24000 or greater), selected portions of the Parkfield region are being mapped to enhance interpretations of the structural geology, geomorphic, and geochronologic data. An apatite fission track study on samples from the Tertiary sedimentary rocks and the granitic rocks permits inference of the exhumation and rock uplift history for the area. The geomorphic analyses help document the geometries and rates of active geologic structures in the area, including the main San Andreas Fault, subsidiary strike-slip faults, and nearby dip-slip faults and folds. Such structures may be identified by their disruption of landforms and young deposits, and their geometries inferred by interpretation of the areal distribution of deformation associated with them. These investigations include establishing a terrace chronosequence for the major drainage system of the area, determining rates of deformation along the active tectonic structures, and improving the paleoseismic record. Rates of transport associated with landslides are being compared with exhumation rates inferred for the same blocks based on the apatite fission track thermochronology. The geologic and geomorphic mapping results and remotely sensed imagery will be compiled in a digital geospatial data system.