【摘要】 利用2001年1月至2008年6月四川固定地震台网和临时地震台站记录到的大量P波到时资料,反演了龙门山断裂带及周边地区的地壳精细三维P波速度模型.结果表明,汶川主震以北和以南地区的结构存在较大差异,以北地区的龙门山断裂带具有很强地壳不均匀性,这与该区发生了大量汶川地震的余震相一致.这些结果有意义地改进了前人对龙门山断裂带仅为不同块体过渡带的认识.汶川主震震源区下方存在有明显低波速异常体,表明流体可能存在于龙门山断裂带内.这些流体可能直接影响汶川大震的形成.本文的成像结果为下地壳流沿龙门山断裂带上浸提供了可靠的地震学证据.更多还原

【Abstract】 In this study we used a large number of P-wave arrival times recorded by the Sichuan permanent and portable seismic stations during January 2001 and June 2008 to obtain a fine threedimensional P-wave tomographic model of the crust around the Longmenshan fault zone. The results show that there exist obvious differences between south and north of the Wenchuan mainshock in the seismic structure. North of the Wenchuan mainshock there exist much more heterogeneities, where many aftershocks occurred. These results have significantly improved over the previous results suggesting that the Longmenshan fault zone is only a transition zone between different blocks. The source area of the Wenchuan mainshock is underlain by obvious low velocity anomalies, suggesting that there exist fluids within the Longmenshan fault zone. These fluids may affect the occurrence of the large Wenchuan earthquake. The present results provide significantly seismological evidence for the upward intrusion of the lower crustal flow along the Longmenshan fault zone.更多还原