Steady contemporary deformation of the central Basin and Range Province, western United States
Steady contemporary deformation of the central Basin and Range Province, western United States
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美国西部盆地省中部的当代稳定变形
DOI：
10.1002/2014jb011145
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
C. Kreemer
中科院分区：
文献类型：
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作者：
W. Hammond;G. Blewitt;C. Kreemer
我们使用来自美国西部GPS网络的数据来估计中部盆地和山脉省（BRP）的构造变形速率、模式和风格。先前的大地测量研究发现，内华达州东部和犹他州西部的地壳作为一个刚性微板块，在测量不确定度内具有零变形率。在GPS时间序列中观察到的瞬态导致其他人提出了一个巨型分离模型，预测中心BRP的行为像微孔板，但具有时变平移。在这里，我们重新评估这些假设，受益于GPS站点和时间跨度的显著增加，以及分析技术的创新。结果表明，BRP地壳无时无刻不在发生变形。在经度- 113.5°和- 116.8°之间的24个站点中，我们发现应变率为1.9±0.2 × 10−9 yr−1，方向为N55°W，方向为2.2±0.2 × 10−9 yr−1，方向为N35°E，与微孔板行为不一致。GPS三联站应变时间序列的线性与准刚性域的幕式平移不一致。一个例外是EGAN站，它表现出在相邻站中没有的非线性运动。内华达的主要信号是与太平洋/北美相对板块运动相一致的分布剪切信号，这表明应力在距离板块边界至少800公里处通过岩石圈传播。观测到的活动伸展与震源机制一致，与地震地质估算的综合速率一致。我们的研究结果不支持BRP中提出的巨型分离。
We use data from western U.S. GPS networks to estimate the rate, pattern, and style of tectonic deformation of the central Basin and Range Province (BRP). Previous geodetic investigations have found the crust of eastern Nevada and western Utah to act as a rigid microplate, with zero deformation rates to within measurement uncertainty. Observed transients in GPS time series have led others to propose a megadetachment model, predicting that the central BRP behaves as a microplate, but with time‐varying translation. Here we reassess these hypotheses, benefiting from a significant increase in GPS stations and time span, and innovations in analysis techniques. Our results show that the BRP crust deforms everywhere and all the time. In a group of 24 stations between longitude −113.5° and −116.8°, we find strain rates of 1.9 ± 0.2 × 10−9 yr−1 extension directed N55°W and 2.2 ± 0.2 × 10−9 yr−1 contraction directed N35°E, inconsistent with microplate behavior. The linearity of time series of strain from GPS station triplets is inconsistent with episodic translation of quasi‐rigid domains. One exception is station EGAN that exhibits nonlinear motion not found in adjacent stations. The dominant signal in Nevada is distributed shear consistent with Pacific/North America relative plate motion, suggesting that stresses are transmitted through the lithosphere at least 800 km from the plate boundary. The observed active extension is consistent with earthquake focal mechanisms and is in agreement with integrated rates estimated from earthquake geology. Our results do not support the proposed megadetachment in the BRP.