Using Dense Seismic Arrays to Determine Structure in the Los Angeles Basin

通过这项研究，我们计划将石油公司调查的地震数据与南加州地震台网的地震地震数据结合起来，以确定洛杉矶盆地地表顶部1-3公里的速度。这一信息很重要，因为它直接关系到由于土壤和地下结构的变化而导致的地震可能产生的震动程度。它将与地面震动的实际测量一起使用，以确定洛杉矶盆地中部的地震危险地图。此外，我们将利用石油公司调查提供的密集覆盖范围来确定盆地的微震活动。这对于理解洛杉矶发生地震的物理过程很重要。地下速度结构将由面波和折射的体波决定。这些波将通过石油公司和地震监测数据的相互关联从环境噪声场中提取出来。产生这些海浪的来源是海洋微震，因此总是存在的。相关将在许多天内完成，并将使用小孔径子阵将背景噪声降至最低。结果将是中央盆地的近地表剪切和压缩波速度图，那里的射线覆盖最密集。然后将近地表速度添加到洛杉矶地区的参考模型(SCEC速度模型)中，形成一个完整的速度模型，可以用来模拟盆地中的地震波。

With this study we plan to combine seismic data from oil-company surveys with the earthquake seismic data from the Southern California Seismic Network to determine the velocity in the top 1-3 km of the surface in the Los Angeles Basin. This information is important because it directly bears on the level of shaking that can be expected from earthquakes due to the variations soils and subsurface structures. It will be used along with actual measurements of ground shaking to determine maps of seismic hazard for the central part of the Los Angeles Basin. In addition, we will use the dense coverage provided by the oil-company surveys to determine the micro-earthquake activity in the basin. This is important for understanding the physical process that generates the earthquakes in Los Angeles.The subsurface velocity structure will be determined by surface waves and refracted body waves. These waves will be extracted from the ambient noise field by cross-correlation of the oil-company and earthquake-monitoring data. The source that generates these waves is ocean microseisms, and hence is always present. The correlations will be done over many days and will use small-aperture sub-arrays to minimize the background noise. The result will be a map of the near-surface shear and compressional wave velocities for the central basin, where the ray coverage is the densest. The near-surface velocities will then be added to the reference model of the Los Angeles region (SCEC velocity model) to make a complete velocity model that can be used to simulated earthquake-generated wave in the basin.