【摘要】 我们率先用钻孔应变仪观测资料研究了地球自由振荡.泰安地震台有差应变和体应变两种钻孔应变观测仪器,都观测到2004年12月26日苏门答腊大地震激发的地球自由振荡.体应变仪观测到地球的球型振荡,而差应变仪观测到地球的环型振荡.两种观测还记录到环型振荡与球型振荡相互的耦合作用.观测也记录到明显的一些振型的谱线分裂现象.用直接观测到的高质量的环型振荡资料求解了0T8~0T19等主要振型的Q值.根据两个方向的剪应变观测数据,求解了环型振荡的最大剪应变方向,发现这个方向是相当稳定的.这种研究表明,高精度钻孔应变观测仪是一种理想的地壳形变观测仪器,可以为地球自由振荡研究提供更丰富的信息.更多还原

【Abstract】 We first studied Earth’s free oscillations using observations of borehole strainmeters. Two kinds of borehole strainmeters at the Tai’an Observation Station, TJ dilatometer and RYR shear strainmeter, both have observed the Earth’s free oscillations excited by the great Sumatra earthquake occurred on December 26, 2004, with dilatometer for spheroidal modes and shear strainmeter for torsional modes. They also observed coupled modes as well as split modes. Q-values of ₀T₈～₀T 19 are determined from high-quality data of torsional oscillations. According to recordings of the RYR borehole shear strainmeter in two perpendicular directions, the torsional oscillation symmetrical axis orientation of the earthquake is calculated and found to be quite steady with time and modes. High-precision borehole strainmeter proved to be ideal for crustal deformation observation and able to provide unique data for researches of Earth’s free oscillation.更多还原