广角地震速度结构反演中的不确定性分析*

doi:10.11978/2015132

Abstract

Abstract: Ocean bottom seismometer (OBS) wide-angle seismic exploration is an important geophysical method to obtain elaborate crust-mantle structure of deep sea. The main theory is to invert the deep crustal structure by refraction and reflection seismic phase and to provide basal seismic information for studying crust structural features. Based on the principle of seismic tomography structure inversion, we aimed at the uncertainty of velocity structure inversion in OBS wide-angle seismic experiment in this study. Several synthetic models and data were built by Tomo2D to study issues such as how different sedimentary layers may influence the inversion result of whole crust velocity structure, how the OBS space may influence the resolving accuracy of high velocity layer (HVL) in lower crust and the effectiveness of identifying the deep crust anomalous bodies. Our results show that the HVL thicker than 4 km can be well inverted and the thinner HVL (<2 km) is poorly inverted for its scale and shape. The deviation of sedimentary thickness in initial model can influence how to identify HVL; the larger deviation corresponds to worse identification. The low-velocity layer within the crust has significant impact on inverting the scale of HVL in lower crust, but the thickness of the low-velocity layer is insignificant. The smallest scale of velocity anomalous body that can be identified is 5 km in the horizontal and 3 km in the vertical when the OBS space is 10 km; and they are 10 km in the horizontal and 3 km in the vertical when the OBS space is 20 km and 30 km.

Key words: ocean bottom seismometer, wide-angle seismic, high velocity layer, velocity structure inversion, South China Sea

CHEN Jinhu, XIA Shaohong, CAO Jinghe, WAN Kuiyuan, QIU Xuelin. Analysis on uncertainty in velocity structure inversion in wide-angle seismic experiments[J].Journal of Tropical Oceanography, 2016, 35(5): 75-87.

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Analysis on uncertainty in velocity structure inversion in wide-angle seismic experiments

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