喀什基准台宽频带井下和地表地震计记录数据对比研究

Earthquake Waveform Comparison of Broadband Records between Borehole and Ground Seismometers in Kashi Seismic Station

对比分析喀什基准台麦盖提井下和相邻地表宽频带地震计记录的背景噪声、麦盖提M_(L)3.1近震和棉兰老岛M_(L)6.6远震波形记录以及功率谱,并进一步研究了相关的震级差和台站下方结构。研究结果表明,井下和地表地震计记录到的波形特征和功率谱既存在相似性,又具有差异性;井下地震计记录的近、远震波形更清晰、简洁,且功率谱也相对较低。麦盖提台站下方地壳厚度约50km,井下地震计下方59m和地表地震计下方47m深度范围内的平均S波速度分别为0.59km/s和0.47km/s。井下地震计得到的近震和远震震级分别比地表地震计得到的震级小0.518和0.025。本文研究结果对合理布设地表和井下地震计,以及利用其观测数据进行地震学研究具有一定的指示意义。

We analyzed and compared the waveforms and power spectrums of background noise of Maigaiti M_(L)3.1 and Mindanao M_(L)6.6 earthquakes recorded by broadband seismometers in borehole and at ground in Maigaiti seismic station in Kashi.We further studied the amplitude differences and structure beneath the Maigaiti station based on the records from borehole and ground seismometers.The results show a more clear and concise waveforms of earthquakes and lower power spectrum recorded by the borehole seismometer and coexistence of both similarity and difference between the waveforms and power spectrums.The crustal thickness is 50km beneath the Maigaiti station.The average S-wave velocities at a range of 0~59m deep beneath the borehole seismometer and 0~47m deep beneath the ground seismometer are 0.59km/s and 0.47km/s,respectively.The magnitudes of local earthquake and teleseism obtained by borehole seismometer are 0.518 and 0.025 smaller than those obtained by ground seismometer,respectively.The results obtained in our studies are useful to the deployment of ground and borehole seismometers as well as seismic study by using their observational data.