Analysis of Regional Phase Data from USArray

来自加州大学圣地亚哥分校(UCSD)斯克里普斯海洋研究所(SIO)的科学家们正在分析美国国家科学基金会(NSF)地球望远镜计划的一部分--来自美国阵列项目的地震图，这些地震图记录了区域距离(200至2000公里)的地震和爆炸。这些数据为美国西部的地壳和上地幔结构提供了新的制约因素。特别是，研究人员正在研究上地幔地震相Pn和Sn，以及地壳相Pg和Lg。该项目包括使用USArrow相位拾取器进行PN层析成像，制作地壳厚度和最上地幔P速度的各向同性和各向异性变化图，这些图在大尺度特征上与以前的结果一致，但在许多区域显示了更详细的情况。初步结果表明，美国阵列中的锡数据具有相当的质量，使联合Pn/Sn值反演能够约束最上地幔结构和各向异性。在许多情况下，可以在USArray数据集中远距离观测到Lg等地壳震相，从而可以对PG和Lg时间和幅度进行综合分析，以解决较低的地壳速度和衰减问题。这些结果补充了横波分裂和面波和体波层析成像研究，为低地壳和最高地幔深度的结构提供了更好的分辨率。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界产生兴趣。该项目通过为研究生提供资金来支持SIO和UCSD的教育计划。结果将通过出版物、会议报告和向SIO的教育和外展计划提供的材料广泛传播。

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.