利用气枪主动源资料研究高频GPS与强震仪信号特征

Investigation on signal characteristics of high-rate GPS and accelerometer by airgun active source experiment

高频GPS在地震学研究中起着重要作用,然而其地震信号的稳定性和适用范围仍不清楚;由于气枪震源可重复性比较高,可提供定量的震源波形信号进行分析,特别适于对仪器的信号特征进行分析和标定.我们根据2016年5月在福建漳州南一水库的气枪主动源激发观测实验获取的高频GPS与强震仪资料,对比分析了不同频率下高频GPS和强震仪的信号特征.研究发现:(1)气枪的沉放深度、枪阵的尺寸以及水深影响两者信号相关性;(2)高频GPS记录到的位移信号与强震仪仿真的位移信号具有高相关性,且在10~60 s频带内两者的波形相关性最高;在长周期上,高频GPS比强震仪稳定性更高.对比发现高频GPS可以作为地震观测的“位移计”,在大震的近场观测中具有其独特的优势,可以作为地震仪观测的有效补充;同时,高频GPS可以应用于地震预警与烈度速报以及快速确定大震破裂过程等工作中.

High-rate GPS plays an important role in seismological research,however,the stability and applicability of its seismic signals are still unclear;benefiting from the relatively high repeatability of airgun seismic sources,it can provide quantitative source waveform signals for analysis,which is especially suitable for analyzing and calibrating the signal characteristics of instruments.We compared and analyzed the signal characteristics of high-rate GPS and accelerometer at different frequency bands based on the information of high-rate GPS and accelerometer obtained from the active airgun source experiment in May 2016 at Nan Yi Reservoir,Zhangzhou,Fujian.It is found that:(1)the sinking depth of the airgun,the size of the gun array and the water depth affect the correlation coefficient between the two types of signals;(2)the displacement record of high-rate GPS is in good consistence with the corrected displacement signal recorded by accelerometer,and the correlation coefficient is highest in the 10~60 s frequency band;and the displacement of high-rate GPS record is more stable than that of accelerometer at longer periods.The comparison shows that high-rate GPS can be used as a“displacement meter”for seismic observation and has unique advantages in the near-field observation of large earthquakes,which can be an effective supplement to seismograph observation.In addition,high-rate GPS can be applied to earthquake early warning,intensity fast reporting,as well as rapid determination of the rupture process of strong earthquakes.