标题： 使用应变计阵列校准DAS记录的应变幅度 显示英文标题

标题： Calibration of the strain amplitude recorded with DAS using a strainmeter array

摘要： 分布式声学传感（DAS）的威力在于它能够仅使用一个探测单元（IU）在光纤上数百个位置采样形变信号。 虽然IU被校准为记录“光纤应变”，但电缆的特性及其与岩石的耦合控制着“应变传递率”，从而决定了“岩石应变”在记录信号中所占的比例。 我们使用地下安装中的DAS记录，以地震信号在0.05 Hz到0.1 Hz之间来现场校准“应变传递率”。 使用了一种紧包层电缆和一种标准松套管通信电缆（并行运行），其中一部分电缆由松散沙子和沙袋加载，与另一部分仅在地板上展开的电缆进行比较。 “应变传递率”根据电缆和安装类型的不同在0.13到0.53之间变化。 沙袋没有显示出明显的影响，而紧包层电缆通常提供更大的“应变传递率”。 相对于应变计的“应变传递率”校准不依赖于波传播参数。 因此，它适用于大振幅地表波信号，在与大圆方向几乎垂直的应变分量中，这种信号的波形与地震仪数据比较无法进行。 在研究的频段内，“岩石应变”的噪声背景约为紧包层电缆在1/6十倍频程内的均方根振幅为0.1 nstrain。 这使得在微震振幅高的时候可以检测到海洋微震。 显示英文摘要

摘要： The power of distributed acoustic sensing (DAS) lies in its ability to sample deformation signals along an optical fiber at hundreds of locations with only one interrogation unit (IU). While the IU is calibrated to record 'fiber strain', the properties of the cable and its coupling to the rock control the 'strain transfer rate' and hence how much of 'rock strain' is represented in the recorded signal. We use DAS recordings in an underground installation near an array of strainmeters in order to calibrate the 'strain transfer rate' in situ, using earthquake signals between 0.05 Hz and 0.1 Hz. A tight-buffered cable and a standard loose-tube telecommunication cable (running in parallel) are used, where a section of both cables loaded down by loose sand and sand bags is compared to a section, where cables are just unreeled on the floor. The 'strain transfer rate' varies between 0.13 and 0.53 depending on cable and installation type. The sandbags show no obvious effect and the tight-buffered cable generally provides a larger 'strain transfer rate'. Calibration of the 'strain transfer rate' with respect to the strainmeter does not depend on wave propagation parameters. Hence it is applicable to the large amplitude surface wave signal in a strain component almost perpendicular to the great-circle direction for which a waveform comparison with seismometer data does not work. The noise background for 'rock strain' in the investigated band is found at about an rms-amplitude of 0.1 nstrain in 1/6 decade for the tight-buffered cable. This allows a detection of marine microseisms at times of high microseism amplitude.