The Huangzhuang-Gaoliying (H-G) fault, located in the northwest edge of Beijing fault depression belt, forms the north segment of the western boundary fault system of the North China Basin. To know the geological characteristics of the fault, a high-resolution seismic exploration, which includes Mini-Sosie vibrator available to the city noise environment, was conducted. The study focuses on the part of the fault through Beijing 2008 Olympic Game Park by using Mini-Sosie method and near-surface seismic profile. Ray tracing method is implemented to design the geometry and estimate parameters in filed data acquisition to meet the requirement for city seismic survey. The decoded principle and the capacity of anti-noise of Mini-Sosie vibrator are analyzed to demonstrate that Mini-Sosie is feasible for the city environment with strong noise. After high-resolution data processing, a seismic depth migration section in the strong noise environment of this survey area was obtained. Results show that the H-G fault is mainly featured as a listric fault with a dip angle ranging from 600 to 400 for depth at ~100 m through 250 m, and has a displacement of about 80 m on the Cenozoic bottom of the depression. Together with previous studies on similar fault systems around the central segment, these findings help to understand the formation mechanism of North China Basin.
Near surface seismic profile holds important information about crust structure at shallow depths. To map subsurface fine structure, near surface seismic methods are especially useful, since the resolution of data for such methods is higher than that in traditional oil and gas industry. As a result, near-surface seismic methods have been widely used in civil engineering, earthquake engineering and archaeology (Buker, et al., 1998; Shtivelman,et al., 1998). In this paper, we will investigate the subsurface structure of the Huangzhuang-Gaoliyin (H-G) fault zone that passes though the center of 2008 Beijing Olympic Park in the northern part of Beijing City. In such an urban area, the seismic source should be portable and a non-explode type, since traditional explode seismic source and wheeled vibrator are forbidden. Therefore, we chose a Mini-Sosie source, a pseudo vibroseis that creates a series of signals with random frequency (Barbier, 1983). This type of seismic source can generate higher frequency signals without destroying the ground surface, and has a strong ability to reduce environmental noise, thereby suitable for city shallow seismic observations (Steeples and Miller, 1998). Such a method has been successfully used in some environmentally sensitive areas (Pratt et al., 2002).
The H-G fault trends in north-northeast direction, and is the northern part of the western boundary fault system of the North China Cenozoic Basin (Figure 1). Deformation of the H-G fault is featured mainly by normal faulting, with the fault plane dipping to the east. On the east side of the H-G fault (fault no. 5 in Figure 1), the Beijing depression was developed in association with the deformation of the Xiadian normal fault (fault no. 8 in Figure 1).