Eikonal Tomography of the Southern California Plate Boundary Region
Eikonal Tomography of the Southern California Plate Boundary Region
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DOI：
10.1029/2019jb017806
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发表时间：
2019-09
期刊：
影响因子：
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通讯作者：
H. Qiu;F. Lin;Y. Ben‐Zion
中科院分区：
文献类型：
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作者：
H. Qiu;F. Lin;Y. Ben‐Zion
我们使用Eikonal层析成像，以获得在南加州的板块边界区域的表面波的相速度和群速度。分析了2014年由346个站距为1 - 30 km的台站记录的2 - 20 s期间的地震噪声数据。瑞利波和勒夫波的相位传播时间是使用垂直-垂直和横向-横向噪声互相关测量的，并且群传播时间是从相位测量导出的。使用每个位置和周期的Eikonal方程，各向同性相速度和群速度以及2-psi方位各向异性通过不同虚拟源的测量进行统计确定。从SCEC共同体速度模型开始，在0.05° × 0.05°网格上联合反演观测到的2.5 - 16 s各向同性相位和群频散曲线，以获得局部一维分段剪切波速度（Vs）模型。与初始模型相比，最终结果在地壳浅部（顶部3-10 km）的Vs通常较低，特别是在盆地和断层带等区域。结果还显示，在圣安德烈亚斯，圣哈辛托，埃尔西诺和加洛克断层明显的速度对比，并建议圣戈尔戈尼奥山口东南的圣安德烈亚斯断层是倾向于东北。对一维Vs反演的非唯一性的研究表明，对顶部3 km Vs结构进行成像需要较短周期（≤2 s）的表面波频散测量或其他类型的数据集，如瑞利波椭圆率。
We use Eikonal tomography to derive phase and group velocities of surface waves for the plate boundary region in Southern California. Seismic noise data in the period range 2 and 20 s recorded in year 2014 by 346 stations with ~1‐ to 30‐km station spacing are analyzed. Rayleigh and Love wave phase travel times are measured using vertical‐vertical and transverse‐transverse noise cross correlations, and group travel times are derived from the phase measurements. Using the Eikonal equation for each location and period, isotropic phase and group velocities and 2‐psi azimuthal anisotropy are determined statistically with measurements from different virtual sources. Starting with the SCEC Community Velocity Model, the observed 2.5‐ to 16‐s isotropic phase and group dispersion curves are jointly inverted on a 0.05° × 0.05° grid to obtain local 1‐D piecewise shear wave velocity (Vs) models. Compared to the starting model, the final results have generally lower Vs in the shallow crust (top 3–10 km), particularly in areas such as basins and fault zones. The results also show clear velocity contrasts across the San Andreas, San Jacinto, Elsinore, and Garlock Faults and suggest that the San Andreas Fault southeast of San Gorgonio Pass is dipping to the northeast. Investigation of the nonuniqueness of the 1‐D Vs inversion suggests that imaging the top 3‐km Vs structure requires either shorter period (≤2 s) surface wave dispersion measurements or other types of data set such as Rayleigh wave ellipticity.