不同裂缝密度的物理模型研究魏建新.pdf

41 4 　　　 V ol.41, No .4 2002 12 GE OPHYSICAL PROSPE CTI NG F OR P ET RO LEU M Dec., 2002 :1000-1441(2002)04-0433-06 魏建新1, 2 (1.石油大学物探重点实验室, 北京1000 83;2.国家地震局地球物理研究所, 北京100081) :, 。 , 。, , , , , , 。(6 %), 。, , 。 :;; :P631.4+1　　　　　　:A A physical model study of different crack densities We J anx nl, 2 (1.T he Un vers ty of Petroleum, Be j ng l00083, Ch na;2.Inst tute of G eo phy s cs, Ch na Se smolog cal Bureau, Be j ng l000 83, Ch na) Abstract:T he effect of crack dens ty and structure on the propagat on of se sm c shear w ave s stud ed throug h labo ra- tory ex per ments w th nst llat o n -controlled crack dens t es.T he phys cal mo dels that are used n the exper ments are made of epoxy res n w th s l con rubber sl m s embedded n them to s mulate the cracks.T he exper ments show that shear w av es are spl t n some deg ree n the or ented crack models of d ff erent crack dens t es.In these models, f ast shear w ave veloc ty s stable, w hereas slow shear w ave veloc ty decreases w th the crack dens ty ncreases.The t me d ff erence of shear w ave spl tt ng s dependent on veloc ty of the slow shear w ave.In case of low crack dens ty (less than 6%), the relat onsh p betw een crack dens t es and veloc t es of the f ast and slow shear w aves ag rees w ell w th theoret cal pre- d ct o n.T he analys s of the slow shear w ave f eld reveals that the polar zat on s reversed w hen the crack shape var es and the dens ty s h g h, but the eff ect of the crack structure on veloc ty s less than that on attenuat on.T hu s prov des another k nd of method to descr be the crack structure and ts character st cs.