Active and passive surface-wave recordings along high-speed lines

Seismic uniform linear arrays (ULAs) with a length of 23.75 m and composed by 96 geophones spaced at intervals of 25 cm were installed in 3 different sites (sites 1, 2 and 3). The ULAs were positioned on the cess (i.e. the track side) along the railway, at approximately 2 m from the rails, on track 1 for site 1 and track 2 for sites 2 and 3. Active seismic data was acquired by vertically striking a metal plate placed in-line, 12.5 cm away from the first (direct shot) and last (inverse shot) geophones.The impact was achieved with a hammer (1.5 kg) and waves propagation along the ULA was recorded for 2 s with a sampling interval of 0.5 ms (i.e. sampling rate of 2 kHz) and a pre-triggering delay of -0.02 s. Six direct and inverse shots were stacked in the time domain to enhance signal-to-noise ratio.HST passages on tracks 1 and 2 were also recorded with the exact same ULAs for durations of 120 s with a sampling interval of 2 ms (i.e. sampling rate of 500 Hz). The recordings were initiated manually upon visual confirmation of approaching trains at the site.地震均匀线列阵（uniform linear arrays，以下简称ULAs）长度为23.75米，由96个间距25厘米的检波器构成，被部署于3个不同测点（测点1、2、3）。ULAs设置在铁路沿线的轨侧路肩（即轨道侧边区域），距钢轨约2米；其中测点1的ULAs布置在1号轨道旁，测点2与测点3的ULAs布置在2号轨道旁。主动地震数据采集采用沿列阵轴线垂直敲击金属板的方式，该金属板距首个检波器（正放炮）与末个检波器（反放炮）均为12.5厘米。敲击动作由1.5千克重锤完成，沿ULAs传播的地震波被记录时长为2秒，采样间隔为0.5毫秒（即采样率为2千赫兹），预触发延迟为-0.02秒。为提升信噪比，对6次正放炮与反放炮数据进行了时域叠加处理。同时，利用完全相同的ULAs对1号和2号轨道上的高速列车（High-Speed Train，简称HST）通行过程进行录制，单段录制时长为120秒，采样间隔为2毫秒（即采样率为500赫兹）。录制工作由现场人员目视确认列车接近后手动启动。