Schouten Thomas L A, Gebraad Lars, Noe Sebastian, Gülcher Anna J P, Thrastarson Solvi, van Herwaarden Dirk-Philip, Fichtner Andreas
Structural Geology and Tectonics, Geological Institute, Department of Earth and Planetary Sciences, ETH Zurich, Sonneggstrasse 5, 8092, Zurich, Switzerland.
Seismology and Wave Physics, Institute of Geophysics, Department of Earth and Planetary Sciences, ETH Zurich, Sonneggstrasse 5, 8092, Zurich, Switzerland.
Sci Rep. 2024 Nov 4;14(1):26708. doi: 10.1038/s41598-024-77399-2.
Determining Earth's structure is paramount to unravel its interior dynamics. Seismic tomography reveals positive wave speed anomalies throughout the mantle that spatially correlate with the expected locations of subducted slabs. This correlation has been widely applied in plate reconstructions and geodynamic modelling. However, global travel-time tomography typically incorporates only a limited number of easily identifiable body wave phases and is therefore strongly dependent on the source-receiver geometry. Here, we show how global full-waveform inversion is less sensitive to source-receiver geometry and reveals numerous previously undetected positive wave speed anomalies in the lower mantle. Many of these previously undetected anomalies are situated below major oceans and continental interiors, with no geologic record of subduction, such as beneath the western Pacific Ocean. Moreover, we find no statistically significant correlation positive anomalies as imaged using full-waveform inversion and past subduction. These findings suggest more diverse origins for these anomalies in Earth's lower mantle, unlocking full-waveform inversion as an indispensable tool for mantle exploration.
确定地球结构对于揭示其内部动力学至关重要。地震层析成像揭示了整个地幔中与俯冲板块预期位置在空间上相关的正波速异常。这种相关性已广泛应用于板块重建和地球动力学建模。然而，全球走时层析成像通常仅纳入有限数量的易于识别的体波震相，因此强烈依赖于震源 - 接收器几何结构。在此，我们展示了全球全波形反演对震源 - 接收器几何结构的敏感性较低，并揭示了下地幔中许多先前未被检测到的正波速异常。这些先前未被检测到的异常中有许多位于主要海洋和大陆内部下方，没有俯冲的地质记录，例如西太平洋下方。此外，我们发现使用全波形反演成像的正异常与过去的俯冲之间没有统计学上的显著相关性。这些发现表明地球下地幔中这些异常的起源更加多样，使全波形反演成为地幔勘探不可或缺的工具。
