Shear velocity structure of the crust and upper mantle of Madagascar derived from surface wave tomography
Shear velocity structure of the crust and upper mantle of Madagascar derived from surface wave tomography
复制标题
表面波层析成像得出的马达加斯加地壳和上地幔的剪切速度结构
DOI：
10.1016/j.epsl.2016.10.041
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发表时间：
2017
影响因子：
5.3
通讯作者：
E. Rindraharisaona
中科院分区：
文献类型：
--
作者：
M. Pratt;M. Wysession;G. Aleqabi;D. Wiens;A. Nyblade;P. Shore;G. Rambolamanana;F. Andriampenomanana;T. Rakotondraibe;R. Tucker;G. Barruol;E. Rindraharisaona
马达加斯加大陆碎片的地壳和上地幔在最近的一系列宽带地震实验之前基本上没有被探测过。在全岛范围内部署宽带地震仪器，使得能够首次研究全岛范围内从表面波得到的相速度变化。晚新生代碱性板内火山活动发生在马达加斯加的三个独立地区（北部、中部和西南部），北部和中部的火山活动持续到<1 Ma，但其来源仍然不确定。三个互补的面波方法（环境噪声，瑞利波互相关，和两个平面波）的组合分析照亮了上地幔的深度为150公里。从三种方法的相速度测量为8-182秒的周期在每个节点相结合，插值生成第一个3-D剪切速度模型亚马达加斯加速度结构。浅（上10公里）低剪切速度区域与西海岸沿着的沉积盆地相关性很好。上地幔低剪切速度带，延伸到至少150公里深的北部和中部地区的近期碱性岩浆活动。这些异常在深度小于100公里时显得很明显，这表明这些区域之间的任何联系都存在于深度大于表面波层析成像分辨率的地方。在板内火山作用西南区50-150公里深处还发现了一个额外的低剪切速度异常。我们解释这三个低速区为岛下的软流圈上涌，产生高海拔地形和相对低量的岩浆活动。
The crust and upper mantle of the Madagascar continental fragment remained largely unexplored until a series of recent broadband seismic experiments. An island-wide deployment of broadband seismic instruments has allowed the first study of phase velocity variations, derived from surface waves, across the entire island. Late Cenozoic alkaline intraplate volcanism has occurred in three separate regions of Madagascar (north, central and southwest), with the north and central volcanism active until <1 Ma, but the sources of which remains uncertain. Combined analysis of three complementary surface wave methods (ambient noise, Rayleigh wave cross-correlations, and two-plane-wave) illuminate the upper mantle down to depths of 150 km. The phase-velocity measurements from the three methods for periods of 8–182 s are combined at each node and interpolated to generate the first 3-D shear-velocity model for sub-Madagascar velocity structure. Shallow (upper 10 km) low-shear-velocity regions correlate well with sedimentary basins along the west coast. Upper mantle low-shear-velocity zones that extend to at least 150 km deep underlie the north and central regions of recent alkali magmatism. These anomalies appear distinct at depths <100 km, suggesting that any connection between the zones lies at depths greater than the resolution of surface-wave tomography. An additional low-shear velocity anomaly is also identified at depths 50–150 km beneath the southwest region of intraplate volcanism. We interpret these three low-velocity regions as upwelling asthenosphere beneath the island, producing high-elevation topography and relatively low-volume magmatism.