The influence of irregular seafloor topography on the seismic wave field and migration imaging
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The influence of irregular seafloor topography on the seismic wave field and migration imaging Fuxing Han1, Kun Wang2, Jianguo Sun1* 1 College for Geoexploration Science Technology, Jilin University, Changchun 130026, China 2 Jilin Communications Polytechnic, Changchun 130012, China
Received 2 May 2018; accepted 15 August 2018 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
One of the problems experienced in marine geophysical exploration is that the layered features in the migration imaging profile are blurred and the seismic energy reflected is weaker in the middle or lower parts. In this study we model the seismic wavefield records in the undulating seafloor when there is both a slight change and significant change in seafloor topography to analyze its influence on the seismic reflection data and migration imaging profiles. We compare and analyze the wave field records collected at the same point on the original and modified velocity models, and the cross-bonding resulting migration imaging profiles. The results show that whether the seismic reflection data collection is performed along the direction of the survey line or against the direction of the survey line, slight changes in the seafloor topography have little effect on the wave field records and the migration profile, while significant changes in the seafloor topography have great effect on both the wave field records and migration profile. Key words: seafloor topography, seismic wave field, seismic reflections, migration imaging Citation: Han Fuxing, Wang Kun, Sun Jianguo. 2019. The influence of irregular seafloor topography on the seismic wave field and migration imaging. Acta Oceanologica Sinica, 38(3): 151–158, doi: 10.1007/s13131-019-1407-5
1 Introduction In recent years, the growing global scarcity of land resources has forced resource exploration shifted from the land to the sea. China has invested a lot of effort and financial resources in marine oil and gas exploration which concentrated in the deep waters of Qiongdongnan Basin, located in the northern part of South China Sea. According to the previous geophysical studies (Tao et al., 2005; Li, 2006; Duan and Zhang, 2006), it is known that the area is characterized by a complex geological structure, with a sudden increase in water depth over a wide range, which changes from a few hundred meters to a few kilometers. As a result, the dip angle suddenly becomes steeper and the sea floor undulates strongly. This kind of structure influences the propagation of seismic wave field energy greatly, thereby affecting the imaging quality of seismic data significantly. Most 2D seismic profiles from this area have the following problems: (1) the structure of the sunken floor is not clear; (2) the basal surface cannot be imaged properly; (3) the reflection is disordered; (4) the signal to noise ratio in the middle and deep layers is low; (5) there are strong multiple waves; (6) the side waves have developed (Zhu et al., 2008; Deng et al., 2010). Pre
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