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近地表沉积层的S速度结构是强地面震动模拟和地震灾害估计的重要参数,尤其是浅部的S波速度结构在工程上具有重要的应用意义.目前大部分资料来源于工程钻孔或工程地震探测,很少有地震波频率范围内的S波速度结构,或者深度达数百米的S波速度结构.通过对天然地震的井下摆波形记录的分析,提供了一种测量地震波频率范围深达数百米的S波速度的有效方法.收集了首都圈地区44个井下摆的近震记录,利用广义射线方法确认了直达S波及其在地表的反射波震相,并通过测量不同台站上两个震相的到时差,获得了首都圈地区浅层100—500m深度范围的S波速度结构.研究发现,浅部100m的平均S波速度低于300m/s.当深度增加到500m时S波速增加到800m/s,平均速度梯度为0.8(m/s)/m.研究结果表明,井下摆地震记录波形是研究沉积盆地浅层S波结构的重要资料,将为沉积盆地的强地面震动模拟提供重要基础参数.
The S-velocity structure of the near-surface sediments is an important parameter for strong ground vibration simulation and seismic disaster estimation, especially the shallow S-wave velocity structure has an important application significance in engineering.At present, most of the data comes from engineering drilling or engineering There are few S-wave velocity structures in the frequency range of seismic waves or S-wave velocity structures with a depth of several hundred meters.On the basis of analysis of downhole waveform records of natural earthquakes, a method is provided to measure the seismic wave frequency range up to An effective method to measure the S-wave velocity of several hundred meters.We collected the records of 44 wells in the metropolitan area and used the generalized ray method to confirm the direct S wave and its reflection phase on the earth surface. The results show that the average S-wave velocity at 100m shallow part is less than 300m / s, and when the depth increases to 500m, the S-wave velocity structure in shallow depth of 100-500m is obtained The wave velocity increases to 800 m / s and the average velocity gradient is 0.8 (m / s) / m. The results show that the downhole seismic waveforms are important data for studying shallow S-wave structures in sedimentary basins, Intended to provide important basic parameters.