Three Component Rotational Ground Motion Obtained from Explosive Source Data
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摘要: 三分量旋转地震动是目前地球物理研究重点之一.利用爆炸震源的平动地震仪观测资料，通过间接计算获得三分量旋转地震动.利用了3炮500 kg炸药的观测资料，3个爆炸点到观测台阵的距离分别是1.8、2.8和8.9 km，计算得到了台阵相对于这3个爆炸点的旋转地震动，其最大峰值旋转角速度分别是41.65、21.98和0.29 μrads/s，与国际同行的旋转地震动结果量级接近.地震动峰值随震中距的衰减是地震工程中关注的问题.提取出三分量的旋转角速度峰值，利用指数函数对三分量的峰值进行拟合，初步得到三分量的旋转地震动角速度峰值随震中距的衰减关系.衰减曲线的主要特征是，1~3 km旋转角速度能量迅速衰减，大于5 km以后衰减逐渐减慢，随着震中距增大曲线的变化越来越趋于平缓.Abstract: Three component rotational ground motion is one of the most important point of geophysics research. In this paper, the rotational ground motions with three components were deduced by calculation using records of translational seismographs from explosions. The observational data used are from three shots with explosive charge of 500 kg for each and observational distances of 1.8, 2.8, 8.9 km respectively. The rotational motions of the array from these three shots were obtained by calculation. The largest peak angular velocities of ground motion are 41.65, 21.98 and 0.29 μrads/s respectively, which are quite near the results from international colleagues. How the peak values of the ground motion decay with the epicenter distance is always the focal problem in earthquake engineering. In this paper, the peak angular velocities of ground motion are fit with exponent function, and the decay of peak values with distance is obtained. The main features of the decay curves are as follows: The values decay very fast within 1-3 km and slow down gradually beyond 5 km. And with the increase of the distance, the curve tends to more and more flat.
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Key words:
- seismology /
- translational--velocity /
- rotational--velocity /
- seismic array /
- explosive source.
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图 3 SP2炮点的平动地震记录和计算出的z分量地面旋转角速度
a.平动地震记录；b.旋转角速度
Fig. 3. Seismic records and z-axis rotational velocities obtained from SP2
图 4 SP2炮点的平动地震记录和计算出的x分量地面旋转角速度
a.平动地震记录；b.旋转角速度
Fig. 4. Seismic records and x-axis rotational velocities obtained from SP2
图 5 SP2炮点的平动地震记录和计算出的y分量地面旋转角速度
a.平动地震记录；b.旋转角速度
Fig. 5. Seismic records and y-axis rotational velocities obtained from SP2
图 6 利用SP1炮的平动地震记录计算出的三分量地面旋转角速度
Fig. 6. Three component ground rotational velocities calculated by the seismic records from SP1
图 7 利用SP3炮的平动地震记录计算出的三分量地面旋转角速度
Fig. 7. Three component ground rotational velocities calculated by the seismic records from SP3
图 8 三分量旋转地震动峰值随震中距的衰减拟合曲线
Fig. 8. Fitting attenuation curve of three component peak ground rotational velocities with the epicentral distance
图 9 三分量峰值平动速度随震中距的衰减关系拟合系数
Fig. 9. Fitting attenuation coefficient of three component peak ground translational velocities with the epicentral distance
表 1 三分量峰值旋转角速度
Table 1. Three component peak ground rotational velocities
炮点编号 Rx Ry Rz 震中距 (km) SP2 30.258 41.651 32.195 1.8 SP1 13.547 21.983 21.010 2.8 SP3 0.180 0.293 0.206 8.9 注：PGRV单位为μrad/s. 
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表 2 三分量峰值旋转角速度随震中距的衰减关系拟合系数
Table 2. Three component fitting attenuation coefficient of peak ground rotational velocities three component with the epicentral distance
拟合系数 Rx Ry Rz A 128.300 0 131.400 0 73.540 0 B -0.802 8 -0.638 5 -0.454 9
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表 3 三分量峰值平动速度随震中距的衰减关系拟合系数
Table 3. Fitting attenuation coefficient of three component peak ground translational velocities with the epicentral distance
拟合系数 Tx Ty Tz A 5.009 0 3.102 0 3.038 0 B -0.669 8 -0.480 3 -0.563 8
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