利用线性密集台阵揭示南襄盆地枣阳凹陷浅层结构及沉积特征OA

Using continuous waveform data collected by 66 nodal seismometers deployed in the Zaoyang sag area of the Nanxiang basin from March to April 2025,cross-correlation calculations were performed to extract 998 Rayleigh wave phase velocity dispersion curves.A direct surface wave inversion method was applied to obtain a high-resolution shear wave velocity structure down to 3 km depth in the region.The H/V spectral ratio method was also used to preliminarily estimate the sediment thickness.A sudden change in the shear wave velocity interface was observed at 15 km along the survey line:the 2.5 km/s contour rises from 2 km depth to 0.5 km depth from north to south,with a variation amplitude of 1.5 km,consistent with the location of the Xiangfan-Guangji fault.Within the 0-15 km range of the survey line,the shear wave velocity characteristics correlate well with the variation in Cretaceous residual thickness in the Zaoyang sag of the Nanxiang basin,indi-cating that the Zaoyang sag was a basin controlled by the western segment of the Xiangfan-Guangji fault during the Cretaceous.Based on the morphology of the basin boundary,it is inferred that the western segment of the Xiangfan-Guangji fault behaved as a normal fault dominated by extension,with strike-slip characteristics,dur-ing the Cretaceous.The fault blocks within the low-velocity zone and the low-velocity continuity near the sur-face reflect the basin sedimentation process from differential block uplift at the early stage of basin formation to stable Neogene sedimentation.