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

板块环流计算表明，太平洋板块相对于北美板块的运动在8 Ma左右由西风向北西方向转变。 这一观测结果与地质数据非常吻合，地质数据表明，在8-10 Ma时，锡耶纳-大峡谷地块相对于科罗拉多高原的运动从西风向西北方向变化。 地质研究表明，在约8 Ma时，加洛克断层以北的东加州剪切带内的右旋剪切速率约为15 mm/年，约占板块相对运动的30%。 大地测量研究表明，现今右旋剪切速率为10-12 mm/年，这为东加州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提供了明确的证据。尽管东加州剪切带在构造上很重要，但它的时空演化仅被广泛了解。 这一建议要求支持调查的运动学系统的板内右旋断层在东加州剪切带的北方的一部分，使用现场绘图，构造地貌，古地震学和地质年代学的综合方法。 拟议的研究是出于目前正在进行的大地测量调查的应变积累和空间分布的幅度在整个东加州剪切带。 鉴于这些大地测量对应变积累的限制，现在正是提高对晚第三纪和第四纪应变释放的时空模式的认识的时候。这两个数据集将提供重要的制约地球动力学假说提出的东加州剪切带的演变。 准确描述东加州剪切带内应变释放的时空模式对于理解与太平洋和北美板块相互作用相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.