Plate boundary localization, slip-rates and rupture segmentation of the Queen Charlotte Fault based on submarine tectonic geomorphology
Plate boundary localization, slip-rates and rupture segmentation of the Queen Charlotte Fault based on submarine tectonic geomorphology
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DOI：
10.1016/j.epsl.2019.115882
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发表时间：
2020-01-15
影响因子：
5.3
通讯作者：
Dartnell, Peter
中科院分区：
文献类型：
--
作者：
Brothers, Daniel S.;Miller, Nathaniel C.;Dartnell, Peter
构造地貌学的一个主要目标是将断层在多个地震周期中的行为与单个地震的行为联系起来，特别是在整个板块边界上。在这里，我们研究了1150公里长，右侧夏洛特皇后费尔韦瑟断层系统使用全面的多波束测深数据沿着夏洛特女王断层（QCF）近海阿拉斯加东南部和西部不列颠哥伦比亚省。精细尺度的构造地貌分析，使我们能够识别和重建184个走滑刺穿点超过630公里的QCF延伸。来自冰川衰退和近海沉积模式的年龄限制产生了类似于50-57毫米/年的一致滑动速率，因为类似于17-12 ka，这是地球上大陆-海洋走滑断层的最快速率。这些滑动率等于或超过全球板块重建的太平洋-北美（PA-NA）相对运动的估计，表明PA-NA运动是高度本地化的。QCF沿沿着一条狭窄且异常笔直的轨迹切割海底，仅在局部跨越处观察到多条断层轨迹。QCF在多个地震周期的几何形状和行为是简单的，典型的成熟断层具有相对均匀的应力场。由于QCF是主要的PA-NA板块边界，我们使用QCF的轨迹来定义相对板块运动的小圆圈路径，并计算相关的欧拉极点。根据新的极点预测的沿走向的一致性变化与观察到的构造地貌，并建议以前的全球板块重建高估的程度，斜收敛沿着QCF。我们还发现，微妙的，长波长（75-150公里）的弯曲和离散的台阶似乎定义了M>7地震的端点，这表明，断裂和由此产生的断层几何形状可能控制破裂分割和粗糙体的发展。最后，沿着QCF的整个长度的预测精度和构造地貌之间的协议迫使区域构造模型的重新评估。在北部，东部亚卡塔地体似乎与太平洋板块一起向西北平移，从QCF转移到费尔韦瑟断层的滑动导致沿南部圣埃利亚斯山脉沿着以20 mm/年的速度收敛。在南部，我们预测沿着QCF西部海达Gulf（类似于5-6毫米/年的缩短，平均）相对于以前的研究收敛率降低。我们的研究结果支持了一个模型，平移和走滑划分沿着边缘的热和弱的太平洋板块，导致地壳增厚和增长的夏洛特女王阶海达Gulf西部。由爱思唯尔公司出版
Linking fault behavior over many earthquake cycles to individual earthquake behavior is a primary goal in tectonic geomorphology, particularly across an entire plate boundary. Here, we examine the 1150-km-long, right-lateral Queen Charlotte-Fairweather fault system using comprehensive multibeam bathymetry data acquired along the Queen Charlotte Fault (QCF) offshore southeastern Alaska and western British Columbia. Fine-scale analysis of tectonic geomorphology allowed us to identify and reconstruct 184 strike-slip piercing points over a 630 km stretch of the QCF. Age constraints from glacial recession and offshore sedimentation patterns yield a consistent slip-rate of similar to 50-57 mm/yr since similar to 17-12 ka, the fastest rate for a continent-ocean strike-slip fault on Earth. These slip-rates equal or exceed estimates of Pacific-North America (PA-NA) relative motion from global plate reconstructions, indicating that PA-NA motion is highly localized. The QCF cuts the seafloor along a narrow and unusually straight trace for its entire length and multiple fault traces are observed only at local step-overs. The geometry and behavior of the QCF over many earthquake cycles is simple and typical of mature faults with relatively homogeneous stress fields. Since the QCF is the primary PA-NA plate boundary, we used the trace of the QCF to define the small circle path for relative plate motion and computed the associated Euler pole. Predicted along-strike obliquity variations based on the new pole agree with observed tectonic geomorphology and suggest that previous global plate reconstructions overestimated the degree of oblique convergence along the QCF. We also find that subtle, long-wavelength (75-150 km) bends and discrete step-overs appear to define the endpoints of M>7 earthquakes, suggesting that obliquity and resultant fault geometry may control rupture segmentation and asperity development. Lastly, the agreement between predicted obliquity and tectonic geomorphology along the entire length of QCF compelled a reevaluation of regional tectonic models. In the north, the eastern Yakatat Terrane appears to be translating northwest with the Pacific plate, and slip transferred from the QCF to the Fairweather Fault results in similar to 20 mm/yr of convergence along the southern St. Elias mountains. In the south, we predict a reduced rate of convergence along the QCF west of Haida Gwaii (similar to 5-6 mm/yr of shortening, on average) relative to previous studies. Our results support a model for transpression and strike-slip partitioning along the edge of a hot and weak Pacific Plate, leading to crustal thickening and growth of the Queen Charlotte Terrace to the west of Haida Gwaii. Published by Elsevier B.V.