Analysis of Regional Phase Data from USArray

来自加州大学圣地亚哥分校斯克里普斯海洋学研究所（SIO）的科学家们正在分析USArray项目（美国国家科学基金会Earthscope项目的一部分）在区域距离（200至2000公里）记录的地震和爆炸的地震图。这些资料为美国西部地壳和上地幔结构提供了新的约束条件。特别是研究上地幔地震相Pn和Sn以及地壳相Pg和Lg。该项目包括使用USArray相位选择进行Pn层析成像，生成地壳厚度和最上层地幔P速度各向同性和各向异性变化的地图，这些地图在大尺度特征上与之前的结果一致，但在许多地区显示了更多细节。初步结果表明，USArray的Sn数据质量相当，使得联合Pn/Sn反演能够约束上地幔结构和各向异性。在许多情况下，USArray数据集可以在很远的距离上观测到Lg等地壳相，从而可以对Pg和Lg的时间和振幅进行综合分析，以解决较低的地壳速度和衰减。这些结果补充了剪切波分裂、表面波和体波断层扫描研究，为地壳下部和上地幔深度的结构提供了更高的分辨率。这项研究将导致美国西部地壳和上地幔结构模型的改进，这将对地质学，构造学和地球动力学社区产生兴趣。该项目通过为研究生提供资金来支持SIO和UCSD的教育计划。研究结果将通过出版物、会议报告以及提供给SIO教育和推广项目的材料广泛传播。

Scientists from Scripps Institution of Oceanography (SIO), University of California, San Diego (UCSD), are analyzing seismograms from the USArray project (part of NSF's Earthscope program) from earthquakes and explosions recorded at regional distances (200 to 2000 km). These data provide new constraints on crust and upper-mantle structure in the western United States. In particular, researchers are studying the upper-mantle seismic phases Pn and Sn and the crustal phases Pg and Lg. The project involves performing Pn tomography using USArray phase picks, producing maps of crustal thickness and both isotropic and anisotropic variations in uppermost mantle P velocity that agree with previous results in their large-scale features but show more detail in many regions. Preliminary results suggest that Sn data in USArray are of comparable quality, enabling joint Pn/Sn inversions to constrain uppermost mantle structure and anisotropy. In many cases, crustal phases such as Lg can be observed to long distances in the USArray dataset, making possible a comprehensive analysis of Pg and Lg times and amplitudes to resolve lower crustal velocities and attenuation. These results complement shear-wave splitting and surface- and body-wave tomography studies by providing superior resolution for structures at lower crustal and uppermost mantle depths. This research will lead to improved models of crust and upper-mantle structure in the western United States, which will be of interest to the geology, tectonics, and geodynamics communities. The project supports the educational program at SIO and UCSD by providing funds for a graduate student. Results will be widely disseminated through publications, conference presentations, and material provided to SIO's education and outreach programs.