Seismotectonics and relative plate motions in the Scotia Sea region
Seismotectonics and relative plate motions in the Scotia Sea region
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斯科舍海地区的地震构造和相对板块运动
DOI：
10.1029/jb094ib06p07293
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发表时间：
1989
影响因子：
--
通讯作者：
D. Wiens
中科院分区：
文献类型：
--
作者：
A. Pelayo;D. Wiens
使用奇异值分解技术对 20 次浅源地震的 P 和 SH 波形和振幅进行震源参数反演，为斯科舍海地区的构造和相对板块运动提供了重要的约束。导出的震源机制显示了沿北斯科舍洋脊的逆冲断层和走滑断层作用以及沿南斯科舍洋脊的正断层和走滑断层作用。火地岛以南的两种逆冲断层机制表明南极板块沿斯科舍板块西缘发生扩散汇聚。地震与沿南设得兰海沟和布兰斯菲尔德海峡的活跃俯冲和后弧扩展一致。两次地震的深度（35公里和55公里）和一次浅逆冲断层事件表明沿南设得兰海沟持续俯冲，但由于板块年龄年轻和俯冲速度慢，俯冲主要是地震性的。布兰斯菲尔德海峡和南斯科舍海岭沿线的正常断层地震的震级和深度表明是弥漫性延伸，而不是典型的有组织的海洋中部扩散，后者通常与较小和较浅的地震有关。八个走滑和逆冲断层事件提供了受良好约束的滑动矢量，显示了斯科舍板块相对于周围较大板块的运动。使用四板块模型（斯科舍省（SC）、南桑威奇（SS）、南极洲（AN）和南美洲（SA））和固定的 SA-AN 欧拉矢量，我们将这些数据与已发布的沿南桑威奇海沟的质心矩张量滑移矢量以及已发布的来自 SS 弧后扩张中心的海洋磁数据一起反演，得出斯科舍地区的第一个定量板块运动模型。 SC-SA欧拉极位于南大西洋，显示出较大的纬度不确定性。 SC-AN 极点受到更好的约束，位于威德尔海。这些结果预测了沿北斯科舍海脊存在压缩成分的左旋走滑运动、沿南斯科舍海脊存在延伸成分的左旋走滑运动以及德雷克海峡的东西向压缩。尽管尚未公布将斯科舍板块与全球板块系统连接起来的速率数据，但欧拉矢量幅度是通过闭包获得的。尽管约束条件较差，但结果表明，沿北斯科舍海脊的相对运动速率为 0.5 厘米/年，沿南斯科舍海脊和德雷克海峡的相对运动速率为 1.0 厘米/年。
Source parameter inversion of P and SH waveforms and amplitudes for 20 shallow earthquakes using a singular value decomposition technique provides important constraints on the tectonics and relative plate motions of the Scotia Sea region. The derived focal mechanisms show both thrust and strike-slip faulting along the North Scotia Ridge and normal and strike-slip faulting along the South Scotia Ridge. Two thrust faulting mechanisms south of Tierra del Fuego indicate diffuse convergence of the Antarctic plate along the western margin of the Scotia plate. Earthquakes are consistent with active subduction and back arc spreading along the South Shetland Trench and Bransfield Strait. The depths of two earthquakes (35 km and 55 km) and one shallow thrust faulting event suggest continued subduction along the South Shetland Trench, but the underthrusting is largely aseismic due to the young plate age and slow subduction rate. The magnitude and depth of normal faulting earthquakes along Bransfield Strait and the South Scotia Ridge are suggestive of diffuse extension rather than typical organized mid-ocean spreading, which is generally associated with smaller and shallower earthquakes. Eight strike-slip and thrust faulting events provide well-constrained slip vectors showing Scotia plate motion relative to the surrounding larger plates. Using a four-plate model (Scotia (SC), South Sandwich (SS), Antarctica (AN) and South America (SA)) and a fixed SA-AN Euler vector, we inverted these data together with published centroid moment tensor slip vectors along the South Sandwich Trench and published marine magnetic data from the SS back arc spreading center to derive the first quantitative plate motion model for the Scotia region. The SC-SA Euler pole is located in the South Atlantic and shows large latitudinal uncertainties. The SC-AN pole is better constrained and located in the Weddell Sea. These results predict left-lateral strike-slip motion with a component of compression along the North Scotia Ridge, left-lateral strike-slip with a component of extension along the South Scotia Ridge, and east-west compression in Drake Passage. Although no rate data have been published connecting the Scotia plate with the global plate system, Euler vector magnitudes are obtained through closure. The results, though poorly constrained, suggest relative motion rates of 0.5 cm/yr along the North Scotia Ridge and 1.0 cm/yr along the South Scotia Ridge and in Drake Passage.