CAJ | 학술논문

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100-500 m深度范围的S波速度结构. 研究发现, 浅部100 m的平均S波速度低于300 m/s. 当深度增加到500 m时S波速增加到800 m/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.
근지표침적층적S속도결구시강지면진동모의화지진재해고계적중요삼수, 우기시천부적S파속도결구재공정상구유중요적응용의의. 목전대부분자료래원우공정찬공혹공정지진탐측, 흔소유지진파빈솔범위내적S파속도결구, 혹자심도체수백미적S파속도결구. 통과대천연지진적정하파파형기록적분석, 제공료일충측량지진파빈솔범위심체수백미적S파속도적유효방법. 수집료수도권지구44개정하파적근진기록, 이용엄의사선방법학인료직체S파급기재지표적반사파진상, 병통과측량불동태참상량개진상적도시차, 획득료수도권지구천층100-500 m심도범위적S파속도결구. 연구발현, 천부100 m적평균S파속도저우300 m/s. 당심도증가도500 m시S파속증가도800 m/s, 평균속도제도위0.8 (m/s)/m. 연구결과표명, 정하파지진기록파형시연구침적분지천층S파결구적중요자료, 장위침적분지적강지면진동모의제공중요기출삼수.
Near surface S velocity of sedimentary layers is crucial for strong motion simulation and seismic hazard assessment. S velocity of the top hundreds' meters is particularly significant for earthquake engineering. While S velocity can be measured by well-logging or shallow seismic survey, it is deduced from the data with frequency band much higher than the band of seismic signals from earthquakes, or the depth profile is too shallow. We present an effective method for resolving near surface velocity structure by modeling borehole seismograms. By analyzing seismograms from hundreds of earthquakes in Beijing region, we have identified direct S and surface-reflected S waves by using generalized ray theory, and determined S velocity structure for the depth of 100-500 m by modeling the interval between the two S waves. The average S velocity is found to be lower than 300 m/s at top 100 m, but increases to about 800 m/s at the depth of 500 m, with an average gradient of 0.8 (m/s)/m. Therefore borehole seismograms are valuable data for studying shallow S-wave velocity structure of sedimentary basins and can provide basic parameters for strong motion simulation in the basins.