全波模型的震相分析

模型震相分析是超声地震模型实验研究中的一项基础性工作。全波模型震相分析法可用来研究震相的初动方向。分析震波位移方向有两种方法,即解析法和矢量法。解析法是通过计算反射和透射系数的正负,来确定反射和透射的位移初动方向;矢量法是按入射波波前位移,考虑波阻抗的相对大小定出主矢量,然后在反射和透射方向上进行分解,从而得到相应波的初动方向。此外在考虑模型表面与接收换能器之间的相对位移对震相的初动方向影响时,尚需考虑仪器性能,换能器的指向性以及发、收换能器的组合。由于衰减和多次反射、透射波的存在,使得某些震相消失了,不同震相波的相干叠加还可能造成假象,使许多震相初动点模糊不清。在震相初动方向分析中,还要同时考虑走时、射线路径、振幅、周期、续至相位等运动学、动力学特征。

Full wave model phase analysis (FPA)

Model phase analysis is the basic work of supersonic seismic model experiment.The full wave model phase analysis can be used to study the first motion direction of waves.We have two methods for analysing the motion directions of seismic waves, namely,analytics and vector method.The analytics determines the directions of first motions of reflected wave and transmitted wave according to the signs of reflection and transmission coefficients.The vector method first determines the principal vector in terms of incident wavefront displacement and the relative magnitude of acoustic impedance at both sides of a reflector, then resolves,principal vector to obtain the first motion, directions of reflected and transmitted waes .When studying how the relative displacement between receiving transducer and model surface influences on the first motion directions of waves, we also consider instrument performance,the directivity of transducer,and the array of transmitting and receiving transducers,Some waves vanish from sight because of attenuation and the presence of multiples an d }.ransmitted waves.The coherence of different waves causes false appearance,making some first motion points blurred, The kinematic and dynamic features,such as travel time, raypath,amplitude, period and secondary arrivals,also must be considered in analysing the first motion direction of waves.