Understanding an evolving diffuse plate boundary with geodesy and geochronology

Plate boundary;Active tectonics;Fault;Slip rate;Geodesy;GPS;Cosmogenic nuclide;Geochronology;Walker Lane;Eastern California shear zone;White Mountains fault zone;Lone Mountain fault;Basin and range

Lifton, Zachery Meyer ; Newman, Andrew V. Earth and Atmospheric Sciences Peng, Zhigang Dufek, Josef Lee, Jeffrey Dixon, Timothy H. ; Newman, Andrew V.

University:Georgia Institute of Technology

Department:Earth and Atmospheric Sciences

关键词: Plate boundary;    Active tectonics;    Fault;    Slip rate;    Geodesy;    GPS;    Cosmogenic nuclide;    Geochronology;    Walker Lane;    Eastern California shear zone;    White Mountains fault zone;    Lone Mountain fault;    Basin and range;   

Others  :  https://smartech.gatech.edu/bitstream/1853/50316/1/LIFTON-DISSERTATION-2013.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

Understanding spatial and temporal variations in strain accumulation and release along plate boundaries is a fundamental problem in tectonics. Short-term and long-term slip rates are expected to be equal if the regional stress field remains unchanged over time, yet discrepancies between modern geodetic (decadal time scale) slip rates and long-term geologic (10^3 to 10^6 years) slip rates have been observed on parts of the Pacific-North American plate boundary system. Contemporary geodetic slip rates are observed to be ~2 times greater than late Pleistocene geologic slip rates across the southern Walker Lane. I use a combination of GPS geodesy, detailed field geologic mapping, high-resolution LiDAR geodetic imaging, and terrestrial cosmogenic nuclide geochronology to investigate the observed discrepancy between long- and short-term slip rates. I find that the present day slip rate derived from GPS geodesy across the Walker Lane at ~37.5°N is 10.6 ± 0.5 mm/yr. GPS data suggest that much of the observed discrepancy occurs west of the White Mountains fault zone. New dextral slip rates on the White Mountains fault zone of 1.1 ± 0.1 mm/yr since 755 ka, 1.9 +0.5/-0.4 mm/yr since 75-115 ka, 1.9 +0.5/-0.4 mm/yr since 38.4 ± 9.0 ka, and 1.8 +2.8/-0.7 mm/yr since 6.2 ± 3.8 ka are significantly faster than previous estimates and suggest that slip rates there have remained constant since the middle Pleistocene. On the Lone Mountain fault I calculate slip rates of 0.8 ± 0.1 mm/yr since 14.6 ± 1.0 ka and 0.7 ± 0.1 mm/yr since 8.0 ± 0.5 ka, which suggest that extension in the Silver Peak-Lone Mountain extensional complex has increased dramatically since the late Pleistocene.