Geologically current plate motions
Geologically current plate motions
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DOI：
10.1111/j.1365-246x.2009.04491.x
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发表时间：
2010-04-01
影响因子：
2.8
通讯作者：
Argus, Donald F.
中科院分区：
文献类型：
--
作者：
DeMets, Charles;Gordon, Richard G.;Argus, Donald F.
我们描述了最佳拟合角速度和MORVEL，这是一组新的闭合强制角速度，用于25个构造板块的地质电流运动，这些板块总共占据了地球表面的97%。海底展开率和断层方位角被用来确定与大洋中脊接壤的19个板块的运动，包括所有主要板块。六个较小的板块很少或根本没有连接到大洋中脊，它们通过GPS站的速度和方位角数据与MORVEL相连。通过设计，全球电路-MORVEL的地质确定的子集和大地约束的子集之间几乎没有运动学信息交换-MORVEL因此平均了所有主要板块在地质间隔内的运动。相对于NUVEL-1A的板块几何变化包括：前非洲板块合并了努比亚、Lwandle和索马里板块，前澳大利亚板块合并了摩羯座、澳大利亚和麦格理板块，前南美板块合并了Sur和南美板块。MORVEL还包括阿穆尔、菲律宾海、孙达兰和扬子板块，使其在亚洲和西太平洋形变研究中比NUVEL-1A更有用。估计了过去0.78百万年来中速和快速扩张中心的海底扩张速率，以及3.16 Ma以来慢速和超低扩张中心的海底扩张速率。费率向下调整0.6-2.6 mm Yr(-1)，以补偿几公里宽的磁反转区。几乎所有NUVEL-1A角速度都与MORVEL角速度有很大不同。因此，许多新的数据、修正的板块几何形状和向外位移的修正大大改变了我们对当前地质板块运动的认识。MORVEL表明，穿越纳斯卡-南极和纳斯卡-太平洋边界的0.78-Myr平均运动明显慢于NUVEL-1A，这与自3.16 Ma以来纳斯卡板块运动的东向分量逐渐减慢一致。它还表明，跨越加勒比海-北美和加勒比海-南美洲板块边界的运动速度是NUVEL-1A的两倍。总而言之，从GPS估计的角速度与MORVEL、NUVEL-1和NUVEL-1A的角速度之间的最小二乘差，NUVEL-1分别比MORVEL-1大260%，NUVEL-1A比MORVEL大50%，这表明MORVEL更准确地描述了历史上的板块运动。当使用MORVEL而不是NUVEL-1A时，纳斯卡板块运动和阿拉伯-欧亚、印度-欧亚板块运动的地质估计和GPS估计之间的显著差异减小了，但没有消除，这可能表明这些板块运动自3.16 Ma以来发生了变化。MORVEL和GPS对北美西部太平洋-北美板块运动的估计只有2.6+/-1.7毫米年(-1)的差异，大约比NUVEL-1A估计的小25%。这对板块的剩余差异，假设在过去1-3Myr期间没有不可识别的系统误差和太平洋-北美运动的可测量变化，表明全球电路中的一个或多个板块发生了变形。对六个三板回路的闭合测试表明，太平洋-科科斯-纳斯卡和苏努比亚-南极两个回路闭合失败，在三个连接处的不闭合速度分别为14+/-5 mm yr(-1)和3+/-1 mm yr(-1)(95%的置信限)。我们得出结论，刚性板近似仍然非常有用，但如果没有任何未知的系统误差，板块可能会发生可测量的变形，可能是热收缩和变形速率接近或低于板块运动学数据中的噪声水平的宽板边界。
We describe best-fitting angular velocities and MORVEL, a new closure-enforced set of angular velocities for the geologically current motions of 25 tectonic plates that collectively occupy 97 per cent of Earth's surface. Seafloor spreading rates and fault azimuths are used to determine the motions of 19 plates bordered by mid-ocean ridges, including all the major plates. Six smaller plates with little or no connection to the mid-ocean ridges are linked to MORVEL with GPS station velocities and azimuthal data. By design, almost no kinematic information is exchanged between the geologically determined and geodetically constrained subsets of the global circuit-MORVEL thus averages motion over geological intervals for all the major plates. Plate geometry changes relative to NUVEL-1A include the incorporation of Nubia, Lwandle and Somalia plates for the former Africa plate, Capricorn, Australia and Macquarie plates for the former Australia plate, and Sur and South America plates for the former South America plate. MORVEL also includes Amur, Philippine Sea, Sundaland and Yangtze plates, making it more useful than NUVEL-1A for studies of deformation in Asia and the western Pacific. Seafloor spreading rates are estimated over the past 0.78 Myr for intermediate and fast spreading centres and since 3.16 Ma for slow and ultraslow spreading centres. Rates are adjusted downward by 0.6-2.6 mm yr(-1) to compensate for the several kilometre width of magnetic reversal zones. Nearly all the NUVEL-1A angular velocities differ significantly from the MORVEL angular velocities. The many new data, revised plate geometries, and correction for outward displacement thus significantly modify our knowledge of geologically current plate motions. MORVEL indicates significantly slower 0.78-Myr-average motion across the Nazca-Antarctic and Nazca-Pacific boundaries than does NUVEL-1A, consistent with a progressive slowdown in the eastward component of Nazca plate motion since 3.16 Ma. It also indicates that motions across the Caribbean-North America and Caribbean-South America plate boundaries are twice as fast as given by NUVEL-1A. Summed, least-squares differences between angular velocities estimated from GPS and those for MORVEL, NUVEL-1 and NUVEL-1A are, respectively, 260 per cent larger for NUVEL-1 and 50 per cent larger for NUVEL-1A than for MORVEL, suggesting that MORVEL more accurately describes historically current plate motions. Significant differences between geological and GPS estimates of Nazca plate motion and Arabia-Eurasia and India-Eurasia motion are reduced but not eliminated when using MORVEL instead of NUVEL-1A, possibly indicating that changes have occurred in those plate motions since 3.16 Ma. The MORVEL and GPS estimates of Pacific-North America plate motion in western North America differ by only 2.6 +/- 1.7 mm yr(-1), approximate to 25 per cent smaller than for NUVEL-1A. The remaining difference for this plate pair, assuming there are no unrecognized systematic errors and no measurable change in Pacific-North America motion over the past 1-3 Myr, indicates deformation of one or more plates in the global circuit. Tests for closure of six three-plate circuits indicate that two, Pacific-Cocos-Nazca and Sur-Nubia-Antarctic, fail closure, with respective linear velocities of non-closure of 14 +/- 5 and 3 +/- 1 mm yr(-1) ( 95 per cent confidence limits) at their triple junctions.We conclude that the rigid plate approximation continues to be tremendously useful, but-absent any unrecognized systematic errors-the platesdeform measurably, possibly by thermal contraction and wide plate boundaries with deformation rates near or beneath the level of noise in plate kinematic data.