Seismic heterogeneities beneath the Atlantic and Africa - thermal or chemical?

我们正计划调查南大西洋和非洲地幔中的地震结构，这些地震结构与层析成像图像中可见的大型低速剪切波异常有关。利用阵列地震学和偏移技术，从地震波场中提取尽可能多的信息，我们将试图确定大剪切波异常是热成因还是化学成因。非洲永久和临时台阵记录的南美洲和南桑威奇群岛的事件将特别阐明南大西洋下方大切变速度异常的边缘。寻找地震构造，利用差分构造（一个事件提供几个深度的构造信息）和波形、频率等信息，可以确定观测到的地震构造的异常程度和物理参数。在以与观测相同的方式分析合成数据之后，将把以地球动力学研究和矿物物理参数为输入的地震建模结果与观测到的地震数据进行比较。利用所有的信息，我们可以测试关于异常起源的不同假设。

We are planning to investigate seismic structures in the Earth s mantle beneath the South Atlantic and Africa, associated with the large low velocity shear wave anomaly that can be seen in tomographic images. Using array seismology and migration and extracting as much information as possible from the seismic wavefield, we will try to determine, whether the large shear wave anomaly has a thermal or chemical origin. Events in South America and South Sandwich Islands recorded at permanent and temporary arrays in Africa will especially illuminate the edge of the large shear velocity anomaly beneath the South Atlantic. Searching for seismic structures and using differential structures (one event gives information on structures in several depths) and information on waveforms, frequencies etc, we can determine the extent of the anomaly and the physical parameters of the observed seismic structures. Seismic modeling results with inputs from geodynamic studies and mineral physical parameters will be compared to the observed seismic data after analysing the synthetic data in the same way as the observations. Using all information, we can test the different hypotheses regarding the origin of the anomaly.