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The strength of tectonic deformation in tectonically complex regions, particularly multi-stage superimposed tectonic regions, can have a significant impact on shale gas preservation conditions. However, differential tectonic deformation has still not been quantitatively constrained, and its impact on the preservation conditions of shale gas is thus poorly understood in the northern Guizhou Province, southwest China. This study investigates the differential preservation conditions of marine shale gas in four eroded synclines (including Shixi, Daozhen, Zhongguan, and Fuyan Synclines) of the northern Guizhou Province. Interpretation of structures in field outcrops, geometry and kinematic analysis, and typical gas reservoir anatomy are combined to quantitatively explore the effect of superimposed deformation on the preservation conditions of shale gas. According to a set of new structural and kinematic constraints, the Riedel shear model for strike-slip faults is firstly conducted in the eroded synclines in the northern Guizhou Province, which innovatively established a linkage between detailed structural analysis and evaluation of shale-gas preservation conditions. We demonstrate that superimposing of deformations plays a role in differential accumulation in eroded synclines. The results indicate that (1) fault strike in the Shixi Syncline is more concentrated than Zhongguan and Fuyan Synclines, whereas fault strikes in the Zhongguan and Fuyan Synclines are more scattered. There is only one direction of maximum principal stress (σ 1) in the Shixi and Daozhen Synclines. There are two maximum principal stress directions (σ 1) in the Zhongguan and Fuyan Synclines. The Zhongguan and the Fuyan Synclines have tensional environments, whereas the Shixi and the Daozhen Syncline have compressional settings; (2) the formation dip angle, distance to a class II fracture, average detachment layer thickness, intensity of superimposed modifications, and interlimb angle may be positively correlated with gas content; (3) the progressive transformation pattern is established. These findings lay the foundation for the future research on the differential preservation mechanism of eroded synclines and may be useful for enhancing research on worldwide strike-slip faults controlling hydrocarbon accumulation. • Riedel shear model first adopted on shale-gas preservation in complex structure zone. • Superimposed deformation was clarified by new structural and kinematic constraints. • Differential shale-gas conceptual accumulation model on eroded synclines is built. • Strike-slip stepwise transformation model for shale-gas accumulation first stressed. [ABSTRACT FROM AUTHOR]

At 8:40 p.m. (Beijing time) on July 23, 2019, a large landslide occurred at Jichang, a village in Shuicheng, Guizhou Province, China, resulting in 42 deaths, 9 missing people, and 21 buildings buried. Field investigation and unmanned aerial vehicle (UAV) photography allow us to characterize this slope failure and analyze its process and causes. Initially, the materials detached from the mountainside and slid over from the slope. Then, the sliding materials partly accumulated in the middle and upper parts of the slope which were blocked by a convex terrain. The rest turned into a high-speed debris flow, divided by the stable block, and descended along two existing gullies at high velocity, and finally decelerating and accumulating. Based on the high-resolution post-sliding DEM data, the original topography of the study area was reconstructed to estimate the volume of the landslide that was about 1,500,000 m3. Based on a first-order evaluation of the landslide kinematics, the whole sliding process of this event lasted about 60 s, the maximum speed was about 25 m/s, and the average speed was 16.6 m/s, indicating a typical high-speed long-runout debris flow. Analysis suggests that continuous heavy rainfall was the dominant factor to trigger this landslide, and the loose weathered regolith and special local topography were the basic intrinsic factors for this event. [ABSTRACT FROM AUTHOR]

On July 23, 2019, a large-scale landslide occurred in Jichang town, Shuicheng County, Liupanshui City, Guizhou Province in China. The landslide, which moved along two gullies, resulted in strong punching-shear, induced scarping on vegetation and large destruction of houses, and finally formed a deposit with a volume of 2 × 106 m3. This research aims to understand the effect of topography on landslide kinematics. To achieve this aim, a detailed field investigation was first carried out with an unmanned aerial vehicle (UAV) aerial photography survey, resident interviews, and field sampling. The rainfall analysis indicates the effective rainfall within 7 days before landslides was 70.14 mm which exceeded the rainfall threshold of 54.3 mm in this region, which finally triggered the landslide. Traditional soil mechanic tests were then performed to identify the soil properties of the source material. Combined with numerical simulation using the nonlinear shallow water equation, the whole process of landslides was divided into four stages: instability stage, acceleration stage, transformation stage, and impact and accumulation stage. The simulations results show the landslide block slid with a low velocity of 8 m/s for about 100 m. Then, Froude number of landslide increases from 2 to 3 when passing the high and steep terrain, indicating that landslide change to inertial dominated with potential same Froude behavior of classic debris flow. The rupture mass slid with the peak velocity of 23 m/s and diverged in two gullies and ran out for about 600 m. The maximum velocity is 23 m/s in east gully while only 15 m/s in west gully. Compared with deep and incised valleys in the west, shallow and straight valley in the east decreases the deposit depth and further increases the velocity of landslide material with increased runout distance. This research may provide a fast flow path of back analyzing geo-hazards on complex terrain and serve as a basis for future research on long runout landslides. [ABSTRACT FROM AUTHOR]