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

使用密集地震台阵确定洛杉矶盆地的结构

• 批准号: 1520081
• 负责人: Robert Clayton
• 金额: $ 39.5万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-11-01 至 2021-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1520081&HistoricalAwards=false
• 关键词: Using; Dense; Seismic; Arrays; Determine

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.

通过这项研究，我们计划将石油公司勘测的地震数据与南加州地震台网的地震数据相结合，以确定洛杉矶盆地地表顶部 1-3 公里的速度。这些信息很重要，因为它直接关系到由于土壤和地下结构的变化而可能发生的地震的震动程度。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地震活动。这对于理解在洛杉矶发生地震的物理过程非常重要。地下速度结构将由表面波和折射体波决定。这些波将通过石油公司和地震监测数据的互相关从环境噪声场中提取。产生这些波浪的源头是海洋微震，因此始终存在。相关性将在许多天内完成，并将使用小孔径子阵列来最大限度地减少背景噪声。结果将是中央盆地的近地表剪切波和压缩波速度图，其中射线覆盖最密集。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，形成完整的速度模型，可用于模拟盆地中的地震波。