地面爆炸地震波的演化及频率特征

Evolution and Frequency Characteristics of Ground Explosion Seismic Wave

对地面爆炸所诱发的地震波进行试验测试,并依据测试结果对其时空演化和频率特征进行了分析。地面爆炸地震波R波前沿陡峭,具有冲击特征。随着距离的增大,质点振动时间逐渐拉长,P、S波逐渐明显且高频分量逐渐增加。P、R波的初振方向在一定距离上发生翻转,原因可能为震源临近区域初振方向由震源函数决定,而远离震源处初振方向由震源函数对时间的导数决定。由于地表有疏松覆盖层,P、S及R波均发生频散现象。频域分析表明,地面爆炸地震波的优势频率带均在5~30 Hz,高于天然地震波。随着距离的增大,某些优势频率成分衰减很快,导致优势频率带发生分裂。

Experiment of ground explosion causing seismic waves was carried out and its evolution in time-space,and frequency pattern were analyzed according to the experiment results.The R wave has a sharp front which shows the impact property of the blast seismic origin.The time length of the wave is enlarged,P and S waves are gradually emerging,and high frequency wave components increase with the increase of distance.The initial directions of the vibrations of P and R waves turn over and the reason may be that the vibration close to the origin is determined by seismic source function,while it is determined by the derivative of seismic source function.All the P,S and R waves are dispersing since there is a loosen layer on the ground.The dominant frequencies are in the range of 5-30 Hz which are higher than those of nature seismic waves.Some dominant frequency components decrease rapidly with the increase of distance,which causes the splitting of the dominant frequency band.