Yanliang Pei

Gravity and magnetic field and tectonic structure character in the southern Yellow Sea

The research of the geophysical survey in the east of the southern Yellow Sea (SYS) (122°-125°E) in 1999 reveals that the SYS has a structure of three-uplifts and two-basins. The structure can be well concordant with the gravity and magnetic anomalies. In the basins, most of the gravity and magnetic anomalies are low and gentle. As well in the uplifts, the gravity anomalies are high positive ones, but the magnetic anomalies are plus and minus variant ones. Seismic data show that the mid-uplift is a Cenozoic one. The Paleozoic is under the Q+N strata, the thickness of which is less than 1 km, with no Palaeogene. The Wunansha uplift area and the Sunan uplift area have good continuity, which indicates that they belong to the same geological unit. The basin in the northern part of SYS, which developed in the late Cretaceous period, is a Cenozoic one mainly made up of Cenozoic sediment. On the contrary, the basin in the southern part is the seaward extension of Subei basin and is a medial Cenozoic sediment basin mainly made up of Cenozoic sediment. Because of the striking left-lateral sense translation of Tanlu fault zone, the east plate of fault zone moved northward on a large scale, which generated a massive north-south pull-apart stress field to make the earth crust pulled apart, revolved and tilted, and the pulling-apart basin came into being in the upper part of the crust.

Assessment of structural stability in Bohai Sea area based on AHP-GDM model

The AHP-GDM model is used for the assessment of structural stability, with the Bohai Sea area as an example. In this model, the credit degree of each expert is calculated through the assessment matrix based on the similarity and diversity of vector. The comprehensive opinions of expert panel are quantitatively obtained by considering the effect of credit degree. According to the geological structural setting, the Bohai Sea is divided into twelve assessment zones of structural stability by non-uniform element method. The structural stability grade of each zone is obtained on the basis of the latest geophysical data, earthquake statistical data, and the information of fault activities, current stress field and crustal deformation. The results show that there are one relatively stable area, three relatively sub-stable areas, six relatively sub-unstable areas and two relatively unstable areas. The assessment results of non-uniform element method are very close with those of uniform grid method with size of 0.25° in longitude direction and 0.14° in latitude direction. However the workload of non-uniform element method is only 1/16 of the latter. Compared with traditional assessment methods of structural stability, a more objective and reliable assessment result can be obtained by combining non-uniform element method and AHP-GDM model.

An aeromagnetic survey system based on an unmanned autonomous helicopter: Development, experiment, and analysis

ABSTRACT China has very long coastline, but special surface conditions make it very difficult to conduct ground magnetic and marine geomagnetic surveys over beach–shallow sea transition areas such as mariculture areas, harbours, and wharfs; as a result, marine survey data cannot be linked to continental survey data, giving rise to missing data. To address this issue, an aeromagnetic survey technology based on an unmanned autonomous helicopter is proposed. Not only is an unmanned autonomous helicopter capable of aeromagnetic surveying the beach–shallow sea transition area inaccessible to vehicles and vessels but its high efficiency and low cost also enable it to be deployed on a vessel, thus making it suitable for aeromagnetic surveying oceanic islands, too. The setup of the aeromagnetic survey system based on an unmanned aerial vehicle (UAV) is introduced, and its trial flight information and processed and analysed magnetic survey data obtained in trial flights are discussed. The measurement accuracy of UAV aeromagnetic data is shown to be comparable to that of marine geomagnetic survey data, and the system effectively compensates for missing magnetic data from inshore and continent–ocean transition zones.

Fault Activity in the Surrounding Sea Areas of the Nuclear Power Plant in Cang-Nan, China

The fault activity in the area surrounding a nuclear power plant is crucial and critical for site selection. This study aims to analyze the fault activity in the surrounding sea areas of the Cang-nan nuclear power plant. The strata information is obtained by both a high-resolution multi-channel seismic survey and a single-channel seismic survey. Based on the processed seismic data, the seismic profiles are interpreted by combining the regional tectonic background and the exploration data from the neighboring nuclear power plant. Seven seismic reflection interfaces are obtained by using the seismic stratigraphy method. According to the active fault criterion, no fault is found in the Quaternary sedimentary layer, indicating that no breakpoint exists. The results show that there is no Quaternary active fault in the concerning area of the Cang-nan nuclear power plant (<25 km) and the site can meet the requirements of the industry standard.