Model for small-scale crustal heterogeneity in Los Angeles basin based on inversion of sonic log data
Model for small-scale crustal heterogeneity in Los Angeles basin based on inversion of sonic log data
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基于声波测井反演的洛杉矶盆地小尺度地壳非均质性模型
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
K. Olsen
中科院分区：
文献类型：
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作者：
W. Savran;K. Olsen
地震工程设计所需的高频地震地面运动（10+Hz）在很大程度上受地壳米级结构的控制。然而，国家的最先进的速度模型很难解决小尺度的地下速度和密度变化的功能。我们反演35声波测井（深度达3000米）在洛杉矶盆地，加利福尼亚州，以获得一个小规模的非均质性的盆地的统计描述。假设一个冯卡门自相关函数，我们的分析发现，赫斯特数，ν，在0.0和0.2之间，垂直相关长度，az，15-150米，标准偏差约为5%的特点，在钻孔数据的变化。我们报告了洛杉矶盆地的平均参数：ν = 0.064（0.058，0.069）± 0.01（0.006，0.012），az = 54（51.1，57.6）± 5.9（1.79，9.53）m，95%置信区间列于括号中。尽管测井深度范围很大，但统计参数随深度变化不大。我们的分析371深度平均剪切波速度在上30米，Vs 30，提供了一个上限的盆地尺度长度估计，由于粗略的采样距离，赫斯特数约为0.3和横向相关长度，ax的5-10公里。
SUMMARY High-frequencyseismicgroundmotion(10+Hz),asneededforearthquakeengineeringdesign purposes, is largely controlled by the metre-scale structure of the earth’s crust. However, the state-of-the-art velocity models poorly resolve small-scale features of the subsurface velocity and density variation. We invert 35 sonic logs (up to 3000 m in depth) in and near Los Angeles basin, CA, to obtain a statistical description of the small-scale heterogeneities of the basin. Assuming a von Karman autocorrelation function, our analysis finds that Hurst numbers, ν, between 0.0 and 0.2, vertical correlation lengths, az, of 15–150 m and standard deviations of about 5 per cent characterize the variability in the borehole data. We report average parameters for Los Angeles basin of ν = 0.064(0.058, 0.069) ± 0.01(0.006, 0.012) and az = 54(51.1, 57.6) ± 5.9(1.79, 9.53)m with 95 per cent confidence intervals listed in the parentheses. Despite the large depth range of the logs, there is no significant variation of the statistical parameters with depth. Our analysis of 371 depth-averaged shear wave velocities in the upper 30 m, Vs30, provides only an upper bound of basin scale-length estimates due to the coarse sampling distance, with a Hurst number of about 0.3 and lateral correlation lengths, ax ,o f 5–10 km.