Assessment of seismic tomographic models of the contiguous United States using intermediate-period 3D wavefield simulation
Assessment of seismic tomographic models of the contiguous United States using intermediate-period 3D wavefield simulation
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使用中周期 3D 波场模拟评估美国本土地震层析模型
DOI：
10.1093/gji/ggab406
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发表时间：
2021
影响因子：
2.8
通讯作者：
Li, Jiaqi
中科院分区：
文献类型：
--
作者：
Zhou, Tong;Xi, Ziyi;Chen, Min;Li, Jiaqi
由于地球望远镜可移动阵列的发展，毗邻的美国已经很好地配备了宽带地震台。以前的研究已经为地壳和上地幔提供了各种分辨率更高的三维地震波速模型。然而，由于数据集和层析成像方法的不同，这些模型之间存在差异，这给北美之下成像的岩石圈结构带来了不确定性。使用最好的数据复盖率和先进的层析成像方法(如全波形反演)进行的进一步模型改进预计将提供更好的地震学约束。初始模型对FWI的收敛有显著影响。然而，如何选择一个最优的初始模型并没有得到很好的研究。在这里，我们提出了一种数据驱动的初始模型选择程序，通过评估来自候选模型的观测和合成之间的波形拟合和失配函数，为连续的美国及其周围地区选择初始模型。我们使用了北美5820个台站记录的30次地震的波形数据集。结果表明，测试的三维模型很好地捕捉到了长周期的波形，而在短周期内表现出了差异，特别是在切向分量上。这表明地壳和上地幔的小尺度非均质性和径向各向异性没有得到很好的约束。基于我们的测试结果，一个混合初始模式结合了S40RTS或S362ANI在地幔和US.2016用于Vsv和CRUST1.0用于地壳Vshin是兼容于未来的FWIs来精炼北美的岩石圈结构。
The contiguous United States has been well instrumented with broad-band seismic stations due to the development of the EarthScope Transportable Array. Previous studies have provided various 3-D seismic wave speed models for the crust and upper mantle with improved resolution. However, discrepancies exist among these models due to differences in both data sets and tomographic methods, which introduce uncertainties on the imaged lithospheric structure beneath North America. A further model refinement using the best data coverage and advanced tomographic methods such as full-waveform inversion (FWI) is expected to provide better seismological constraints. Initial models have significant impacts on the convergence of FWIs. However, how to select an optimal initial model is not well investigated. Here, we present a data-driven initial model selection procedure for the contiguous US and surrounding regions by assessing waveform fitting and misfit functions between the observations and synthetics from candidate models. We use a data set of waveforms from 30 earthquakes recorded by 5820 stations across North America. The results suggest that the tested 3-D models capture well long-period waveforms while showing discrepancies in short periods especially on tangential components. This observation indicates that the smaller scale heterogeneities and radial anisotropy in the crust and upper mantle are not well constrained. Based on our test results, a hybrid initial model combining S40RTS or S362ANI in the mantle and US.2016 forVsvand CRUST1.0 forVshin the crust is compatible for future FWIs to refine the lithospheric structure of North America.