Accommodation of missing shear strain in the Central Walker Lane, western North America: Constraints from dense GPS measurements
Accommodation of missing shear strain in the Central Walker Lane, western North America: Constraints from dense GPS measurements
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DOI：
10.1016/j.epsl.2016.01.015
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发表时间：
2016-04
影响因子：
5.3
通讯作者：
J. Bormann;W. Hammond;C. Kreemer;G. Blewitt
中科院分区：
文献类型：
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作者：
J. Bormann;W. Hammond;C. Kreemer;G. Blewitt
我们提出了264个新的震间GPS速度从移动的阵列的GPS为内华达州transtension（MAGNET）和连续的GPS网络，测量太平洋-北美板块边界变形的中央步行者巷。相对于北美固定的参考系，西北方向的速度从盆地和山脉省的12.4毫米/年平稳增加到内华达州中部的12.2毫米/年，导致中央步行者车道的变形预算为12.8毫米/年。我们使用一个弹性块模型来估计断层滑动和块旋转速率和模式的GPS速度的变形。右侧剪切分布在整个中央步行者巷，块体模型预测的走滑率一般<1.5 mm/年，但延伸率最高的是沿内华达山脉前缘断层系统发现的北向正断层附近，以及从步行者湖延伸到太浩湖的左步进、雁列系列不对称盆地。在西部中央步行者巷的新构造研究发现，在不对称盆地的走滑或斜断层的证据很少，提示建议，在这个地区的右旋变形是通过顺时针块旋转容纳。我们测试这一假设，并表明，一个模型只依赖于顺时针块旋转和正常的断层相结合，以适应右旋扭张应变积累系统不适合GPS数据与我们的首选模型相比。这表明，斜向或分割的右侧断层滑动的一些组件是需要适应剪切在西部中央步行者巷的不对称盆地。现今博迪丘陵、卡森域和米纳偏折区的顺时针垂直轴旋转速率在1 - 4 °/百万年之间，低于已发表的古地磁旋转速率，表明自中新世晚期至中期以来，块体旋转速率有所降低。
We present 264 new interseismic GPS velocities from the Mobile Array of GPS for Nevada Transtension (MAGNET) and continuous GPS networks that measure Pacific–North American plate boundary deformation in the Central Walker Lane. Relative to a North America-fixed reference frame, northwestward velocities increase smoothly from ∼4 mm/yr in the Basin and Range province to 12.2 mm/yr in the central Sierra Nevada resulting in a Central Walker Lane deformation budget of ∼8 mm/yr. We use an elastic block model to estimate fault slip and block rotation rates and patterns of deformation from the GPS velocities. Right-lateral shear is distributed throughout the Central Walker Lane with strike-slip rates generally <1.5 mm/yr predicted by the block model, but extension rates are highest near north-striking normal faults found along the Sierra Nevada frontal fault system and in a left-stepping, en-echelon series of asymmetric basins that extend from Walker Lake to Lake Tahoe. Neotectonic studies in the western Central Walker Lane find little evidence of strike-slip or oblique faulting in the asymmetric basins, prompting the suggestion that dextral deformation in this region is accommodated through clockwise block rotations. We test this hypothesis and show that a model relying solely on the combination of clockwise block rotations and normal faulting to accommodate dextral transtensional strain accumulation systematically misfits the GPS data in comparison with our preferred model. This suggests that some component of oblique or partitioned right-lateral fault slip is needed to accommodate shear in the asymmetric basins of the western Central Walker Lane. Present-day clockwise vertical axis rotation rates in the Bodie Hills, Carson Domain, and Mina Deflection are between 1–4°/Myr, lower than published paleomagnetic rotation rates, suggesting that block rotation rates have decreased since the Late to Middle Miocene.