Xinxiang-Shangqiu Fault starts from Yuhekou in the west and extends eastward into Anhui Province through Xinxiang, Yanjin, Fengqiu, Lankao, Minquan, Shangqiu and Xiayi, with a total length of about 400km and a general strike of NWW. It is a regional concealed fault in Henan Province and a boundary fault between northern North China depression and southern North China depression.

This study focuses on the Fengqiu section of Xinxiang-Shangqiu Fault, which is the boundary structure between the Kaifeng sag, Neihuang uplift and Dongpu sag. Controlled by the NE-NEE trending Changyuan Fault and Yellow River Fault at its east and west end, this fault section has a length of about 30km and controls the Mesozoic to early Cenozoic sedimentation in the Kaifeng sag and the south side of Dongpu sag.

In this paper, the shallow structural characteristics and Quaternary activities of Fengqiu section of the Xinxiang-Shangqiu Fault are revealed by the combination of reflection seismic exploration and drilling detection. Two shallow seismic exploration profiles and one composite drilling geological section are arranged across the fault.

The results of shallow seismic exploration show that the Fengqiu section of Xinxiang-Shangqiu Fault is NWW trending. It is a north-dipping normal fault accompanied by several nearly parallel normal faults, and the fault is still active since the Quaternary.

In the composite drilling geological section at Yaowu, the latest faulted stratum is a clay layer between borehole YW5 and YW7, and the buried depth of the upper breakpoint is between 57.00~61.50m. Combined with the dating results of the collected samples, it is comprehensively judged that the latest activity age of Fengqiu section is the middle of late Pleistocene. Since the middle of late Pleistocene, the whole region is in a relatively stable tectonic period. It is verified that the comprehensive detection method of shallow seismic exploration with drilling can effectively find out the accurate location of hidden faults.

The zone with strong vertical differential movement is often the zone where earthquakes occur. The vertical differential movement between Kaifeng sag and Neihuang uplift is very strong, and the difference reaches nearly 1^{}000 meters since Neogene. Moreover, the structural pattern of the main strong earthquakes in the North China Plain is characterized by zoning in NE direction and segmentation in NW direction, especially at the intersections of NWW-trending faults and NE-trending faults. The Xinxiang-Shangqiu Fault intersects with a series of NE-NEE trending faults, including Tangdong, Changyuan, Yellow River and Liaolan faults from west to east. The Fengqiu section is at the intersection with the Changyuan Fault and the Yellow River Fault, and is located in the Fengqiu M6.5 potential seismic source area of the North China plain seismic belt. The intersection of two groups of Quaternary active faults is a favorable place for the preparation and generation of moderate and strong earthquakes. Therefore, the research results provide seismological basis for the site selection of major engineering projects, urban planning and construction in this area, and have reference value for discussing the geodynamic issues such as deep and shallow structural relationship and structural evolution of Xinxiang-Shangqiu Fault.

As one of the rhombic blocks in North China, Kaifeng depression is on the south of the northern Huabei depression and in the north of the southern Huabei depression, bounded by Xinxiang-Shangqiu Fault and Zhengzhou-Kaifeng Fault, respectively. So far, the activity of Zhengzhou-Kaifeng Fault during Kainozoic era and the relationship between Zhengzhou-Kaifeng Fault and Xinxiang-Shangqiu Fault is still unknown. We interpreted several deep seismic profiles across Taikang uplift and Kaifeng depression on the basis of the strata sequence exposed by the 8 drill holes in the related area. The outcomes indicate that the Zhengzhou-Kaifeng Fault strikes EW on the whole, presenting undulating feature in plain, with a length about 154km. The profiles show the dip angle of the fault is steeper in the shallow than that in the deep, with an obvious "L-shaped" turning point. In Paleogene, the fault was a normal fault. In its hanging wall, the Kaifeng depression, there deposited hundreds of meters of Eogene. After middle Himalayan movement, Zhengzhou-Kaifeng Fault converted to a strike-slip fault, the dip angle became steeper, but the activity became weaker. The Zhengzhou-Kaifeng Fault ended its activity before Quaternary. As a response to the compression in the footwall caused by the sustained sinistral shearing, there developed a series of NW-trending, en echelon wide and gentle folds. Then, the activity in Kaifeng depression shifted to its north boundary.

On the basis of dividing and comparison of the Neogene strata and their bottoms revealed by 7 drill holes in Taikang area, we completed 101 seismic profiles with a total length of 4991km. Seismic data were compared and interpreted. The results indicate that Xinzheng-Taikang Fault, as a blind fault extending from Xinzheng to Taikang, which was considered as an EW striking fault from Xuchang to Taikang before, is the boundary of Taikang uplift and Zhoukou depression, controlling the sedimentation since Neogene Period. So we named the fault the Xinzheng-Taikang Fault, which is composed of two branches, mainly, the east and west branches. The west branch strikes northwest, dipping northeast with steep angles, and the fault plane extending more than 140km in length. As revealed on the seismic profiles, the eastern segment of the west branch is normal fault, while the west segment of the branch shows characteristics of strike-slip fault. The east branch trends NW-NEE, dipping SW-SSE with the length of about 50km. Two branches form a minus flower structure, indicating the strike slip-extension tectonic background. The bottom of Neogene strata is offset about 120m by the east branch, 20m by the west branch, and the bottom of Quaternary is probably offset too. Meanwhile, latest studies suggest that the composite strip of the two branches of Xinzheng-Taikang Fault, which is a tectonic transfer zone, is the subduction zone between the two strike-slip faults. The tectonic stress tends to be released by the east-west branch fault, and the zone should be the seismogenic structure for the recent seismicity in Taikang area. In 2010, the latest earthquake ofM_S4.7 occurred in this area, causing 12 people wounded. The seismogenic structure was considered to be the Xinzheng-Taikang Fault. So locating the fault exactly is of great importance to disaster prevention.