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For the purpose of batter evaluating ground fissure susceptibility (GFS), this study developed a hybrid model based on factor optimization and support vector machines (SVM). Firstly, an evaluation index system of GFS was established containing 15 influence factors. Then, the data sample was normalized by certainty factors (CF) for the preparation of data analysis and machine learning. In the process of factor optimization, Schmidt orthogonalization (SO) was used to reduce collinearity in the data, and Pearson correlation coefficient (PCC) analysis was utilized to estimate its effect. Following, the principal component analysis (PCA) was applied to integrate and reduce the dimension of samples, and 9 component vectors were selected for the construction of SVM eventually. In the procedure of SVM modeling, the modeling data set was composed of 140 land fissure data and 140 non-deformation points. The cross-validation (CV) method was adopted to determine the required parameters, and the performance of the completed model was verified by statistical analysis and receiver operating characteristic (ROC) curve. The prediction accuracy of the final model reached a level of 0.852 with selected parameters. Finally, the GFS values of whole data in the study area were calculated by the trained model, and the GFS map was produced with its effect assessed. In conclusion, the model in this research can evaluate the GFS accurately and has a high value in both scientific research and engineering application. [ABSTRACT FROM AUTHOR]

The pavements of the Beijing Capital International Airport (BCIA), China, where a buried fault zone lies beneath, have undergone continuous severe damages since 2008, but its causes remain unclear. This study focuses on the combined effect of moving aircraft loads and a buried fault zone existence, considering the enormous number of airport operations at the BCIA and the complex conditions of the pavement structure. Hence, a series of numerical simulations conducted using the three-dimensional finite element model were performed. Two models were developed in this study. Model 1 contained a buried fault zone, whereas model 2 did not. The simulation scenarios in each model include a low-speed scenario (scenario 1), a moderate-speed scenario (scenario 2), and a high-speed scenario (scenario 3). Our results show that the most evident deflections caused by the aircraft loads were largely concentrated on the pavements built on the fault zone. The maximum vertical displacement after loading once in model 1 was determined as 0.5 ~ 0.7 mm, whereas in model 2 was 0.4 ~ 0.5 mm. The greatest vertical displacements were generated in scenario 1 rather than in scenario 3, in both models 1 and 2. Moreover, the maximum shear strains on the pavement surface in model 1 are about 2 ~ 19 times larger than in model 2. These findings suggest that aircraft moving loads in the BCIA, especially the low-speed loads, contributed a lot to the recurrent pavement faulting and demonstrate the adverse effects of the buried fault zone on pavement performance. [ABSTRACT FROM AUTHOR]

Earth fissures (EF) form in the northeastern Beijing Plain, causing horizontal and vertical displacements of the ground surface and damaging hundreds of buildings and roads. In addition, since 2009, an unprecedented number of cracks with vertical offsets have occurred in the Beijing Capital International Airport (BCIA), which is the busiest airport in China, causing serious financial losses and increasing the risk of air travel. The EF were divided into three groups, including EF1, EF2, and EF3, based on their distribution and deformation patterns. In general, the EF1 and EF2 fissures formed along segments of the NE-SW trending regional normal faults and have large vertical offsets but small widths. The deformation patterns, trenches and geophysical prospecting profiles, demonstrate that the EF1 and EF2 fissures propagated from the preexisting faults. In contrast, the EF3 fissures formed in a disorganized pattern above the paleochannels of the Chaobai River with short lengths and negligible vertical offsets. The monitoring data for the EF1 fissures indicates that the formation and deformation of the EF in the northeastern Beijing Plain were induced by groundwater pumping. The formation processes of the EF1, EF2, and EF3 fissures are classified into two categories: (1) on the existence of preexisting normal faults and (2) on the existence of paleochannels. Two hypothetical conceptual models are presented to illustrate the formation processes. [ABSTRACT FROM AUTHOR]

Using the US Geological Survey (USGS) finite fault model, the co-seismic horizontal displacement and horizontal principal stress field in North and Northeast China generated by the Tohoku-Oki M9.0 earthquake of March 11th, 2011, were retrieved by linear elastic finite element numerical simulation. On this basis, the static Coulomb failure stress variations of the main active faults and tectonic zones in North and Northeast China were calculated, and the triggering effect of the earthquake on seismicity in North and Northeast China was discussed. Results were as follows: (1) the co-seismic horizontal displacement field caused by the great earthquake was eastward in North China; the maximum value, which occurred in the Shandong Peninsula and north Jiangsu Province, was about 12 mm; and the values gradually decreased from east to west. The co-seismic horizontal displacement field in Northeast China was SE-SEE and the maximum value, which occurred in northeast Jilin Province, was about 30 mm. The simulated results for the co-seismic horizontal displacement field were in good agreement with GPS observational results. (2) The near-surface co-seismic maximum horizontal principal stress (ΔσHmax) was tensile stress ranging from 0 to 2.0 KPa. From Northeast China to North China, the direction gradually altered from NW to NWW to nearly EW to NEE. The co-seismic minimum horizontal principal stress (ΔσHmax) was compressive as well as tensile stress, with a magnitude of 0-0.75 KPa, which is approximately equal to zero. From Northeast China to North China, the direction gradually changed to NNW from NE to NNE to nearly NS. Although the co-seismic stress effect generated by the great earthquake had some effect on the present tectonic stress field of North and Northeast China, its influence was too slight to change the present framework of the regional tectonic stress field. (3) Coulomb failure stress variations on active fault zones in North and Northeast China mainly increased; however, the amount of increase was less than 1 KPa. The increases were largest in the middle and northeastern segments of the Tancheng-Lushan fault zone and the Mishan-Dunhua fault zone. The Tohoku-Oki Mw9.0 earthquake did have some triggering effect on seismic activity in North and Northeast China, but the effects were limited. [ABSTRACT FROM AUTHOR]

After the Wenchuan M 8.0 Earthquake, which occurred on May 12, 2008, in Sichuan Province, China, we conducted a series of hydraulic fracturing stress measurements in three 200 m deep boreholes (ZK01, ZK02, and ZK03) drilled in Beichuan and Jiangyou regions near the northeastern segment of Longmenshan fault belt in 2009. These measurements revealed the near-surface stress field in the fault region one year after the Wenchuan M 8.0 Earthquake. However, the lack of the stress measurements before the earthquake in the same region makes it difficult to understand variations of the in situ stress field (near-surface) by comparative analysis. In order to determine the unknown horizontal principal stresses before the earthquake in Beichuan and Jiangyou regions, the following research method was tentatively applied. Firstly, we calculate the static co-seismic stress field by linear elastic finite element numerical simulation with ANSYS, based on the co-seismic static displacement generated by the Wenchuan M 8.0 Earthquake along the central Longmenshan fault plane in Beichuan and Jiangyou. Secondly, combining hydraulic fracturing measurements (after the earthquake) with the co-seismic stress (simulation), the magnitudes and orientations of horizontal principal stresses before the earthquake were calculated. Finally, the variation of the in situ stress (near-surface) in Beichuan and Jinagyou, both before and after the Wenchuan M 8.0 Earthquake, were obtained by comparative analysis. To do this the magnitude of S was decreased on average by 13.01 and 6.54 MPa after the earthquake in ZK02 and ZK03, respectively and the magnitude of S was decreased by 2.54 and 5.29 MPa in ZK02 and ZK03, respectively. Following the earthquake, the average direction of S rotated anticlockwise by 42.5°. [ABSTRACT FROM AUTHOR]

The crustal stress and seismic hazard estimation along the southwest segment of the Longmenshan thrust belt after the Wenchuan Earthquake was conducted by hydraulic fracturing for in-situ stress measurements in four boreholes at the Ridi, Wasigou, Dahegou, and Baoxing sites in 2003, 2008, and 2010. The data reveals relatively high crustal stresses in the Kangding region (Ridi, Wasigou, and Dahegou sites) before and after the Wenchuan Earthquake, while the stresses were relatively low in the short time after the earthquake. The crustal stress in the southwest of the Longmenshan thrust belt, especially in the Kangding region, may not have been totally released during the earthquake, and has since increased. Furthermore, the Coulomb failure criterion and Byerlee's law are adopted to analyzed in-situ stress data and its implications for fault activity along the southwest segment. The magnitudes of in-situ stresses are still close to or exceed the expected lower bound for fault activity, revealing that the studied region is likely to be active in the future. From the conclusions drawn from our and other methods, the southwest segment of the Longmenshan thrust belt, especially the Baoxing region, may present a future seismic hazard. [ABSTRACT FROM AUTHOR]