Collaborative Research: Recent Kinematic Evolution of the Northern Eastern California Shear Zone from Geologic Data

板块电路计算表明，太平洋板块相对于北美板块的运动在~8 Ma由西风向北西向转变。这一观察结果与地质资料非常吻合，表明西尔兰-大谷地块相对于科罗拉多高原的运动在~8-10 Ma由西风向西北运动转变。地质研究表明，加洛克断裂以北的加州东部剪切带内约8 Ma的右旋剪切速率约为15 mm/年，约占板块相对运动的30%。大地测量学研究表明，现今的右旋剪切速率为10-12毫米/年，这提供了明确的证据，表明加州东部剪切带仍然是太平洋-北美板块边界带内变形的重要组成部分。尽管它在构造上具有重要意义，但东加州剪切带的大部分时空演变只被广泛地理解。这项提议要求支持使用野外测绘、构造地貌学、古地震学和地质年代学的综合方法来调查加州东部剪切带北部板内右旋断层系统的运动学。这项拟议的研究是由正在进行的关于现今应变积累的大小和整个东加州剪切带的空间分布的大地测量调查推动的。鉴于这些对应变积累的大地测量约束，提高对新近纪晚期和第四纪应变释放的时空模式的认识是及时的。这两个数据集将为为加州东部剪切带的演化提出的地球动力学假说提供重要的约束。准确描述加州东部剪切带内应变释放的空间和时间模式，对于了解与太平洋和北美板块相互作用有关的更广泛的板内变形区域的构造过程至关重要。

Plate circuit calculations indicate that motion of the Pacific plate relative to North American plate changed from westerly to NW at ~8 Ma. This observation corresponds extremely well with geologic data which indicates that motion of the Sierran-Great Valley block relative to the Colorado Plateau changed from westerly to NW at ~8-10 Ma. Geologic studies indicate that the rate of right lateral shear at ~8 Ma within the Eastern California Shear Zone north of the Garlock fault was ~15 mm/yr accounting for ~30%of relative plate motion. Geodetic studies indicate a present-day dextral shear rate of 10-12 mm/yr, providing clear evidence that the Eastern California Shear Zone is still an important component of deformation within the Pacific-North America plate boundary zone. In spite of its tectonic importance, the space-time evolution of much of the Eastern California Shear Zone is only broadly understood. This proposal requests support for investigating the kinematics of a system of intraplate dextral faults in the northern part of the Eastern California Shear Zone using an integrated approach of field mapping, tectonic geomorphology, paleoseismology, and geochronology. The proposed research is motivated by ongoing geodetic investigations on present-day magnitude of strain accumulation and spatial distribution across the Eastern California Shear Zone. In light of these geodetic constraints on strain accumulation, it is timely to improve the understanding of the spatial and temporal patterns of strain release during the late Neogene and Quaternary. The two data sets will provide important constraints on geodynamic hypotheses proposed for the evolution of the Eastern California Shear Zone. An accurate characterization of the spatial and temporal patterns of strain release within the Eastern California Shear Zone is crucial for understanding tectonic processes over a much broader area of intraplate deformation associated with the interaction of the Pacific and North American plates.