Rayleigh面波衰减特性与汶川地震关系研究

We selected 489 pairs of Rayleigh wave from 7321 wavefoms recorded by 72 stations in continental China. The pure-path attenuation coefficients of the Rayleigh wave for each cell in China are attained by inversting each cell after getting mix-path attenuation coefficients by the phase-matched method and the frequency-domain Wiener filter was used．We conclude that the attenuation of Rayleigh wave is lower in Sichuan basin than Songpan-Ganmzi fold belt at short period,that is 20~50km,which shows this depth is upper mantle in east china and crust in west china; Also we think that there is a close connection between the distribution of seismic wave attenuation and large earthquke.Wenchuan earthquake and it's aftershocks occurred the transitional zone of high attenuation in Sichuan and low attenuation in eastern Qinghai-Tibet plateau and close to low attenuation area and that occurred in the crust above high attenuation zone. And we think there is a wedge high attenuation in crust in Songpan-Ganmzi fold belt, which extend to Yangzi block. At the same time, we found Sichuan basin doesn't dive to Longmen mountain, and the main reason of Wenchuan earthquake is that upper crust decouple from high attenuation in Songpan-Ganmzi fold belt forming Spade thrust-nappe structure.