No abstract

Landslides cause a considerable amount of damage around the world every year. Landslide susceptibility assessments are useful for the mitigation of the associated potential risks to local economic development, land use planning, and decision makers. The main aim of this study was to present a novel hybrid approach of bagging (B)-based kernel logistic regression (KLR), named the BKLR model, for spatial prediction of landslides in the Shangnan County, China. We first selected 15 conditioning factors for landslide susceptibility modeling. Then, the prediction capability of all conditioning factors was evaluated using the least square support vector machine method. Model validation and comparison were performed based on the area under the receiver operating characteristic curve and several statistical-based indexes, including positive predictive rate, negative predictive rate, sensitivity, specificity, kappa index, and root mean square error. Results indicated that the BKLR ensemble model outperformed and outclassed the KLR and the benchmark support vector machine model. Our findings overall confirmed that a combination of the meta model with a decision tree classifier based on a functional algorithm can decrease the over-fitting and variance problems of data, which could enhance the prediction power of the landslide model. The resultant susceptibility maps could be useful for hazard mitigation in the study area and other similar landslide-prone areas.

No abstract

Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics, provenance, and tectonic implications. Petrographic features show that the sandstones are characterized by low‐medium compositional maturity and textural maturity. The CIA and CIW values reveal weak and moderate weathering history in the source area. The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature, while the provenance of the western and southwestern sediments were mainly from the Qinling‐Qilian Orogenic Belt. The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc, which is closely related to the evolution of the Qinling‐Qilian Orogenic Belt. However, the sandstones in the northwestern Ordos Basin show complex features, which may be resulted from a typical recycling process. Overall evidence from petrography, geochemistry and sedimentology, together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin, respectively, and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin, where a large, uniform sediment dispersal system developed during the Late Triassic.

Multi‐scale intracontinental deformations were developed in response to the tectonic evolution of the southern Longmenshan tectonic belt (LMS) on the eastern margin of the Tibetan Plateau. Detailed studies, including field structural analysis and anisotropy of magnetic susceptibility (AMS), were conducted on sedimentary rocks in the foreland basin of the southern Longmenshan tectonic belt (FBSL) in order to better understand the tectonic evolution of the southern LMS. Field observations show that FBSL deformations are mainly characterized by broad and gentle folds in a NE–SW direction and shallow thrust faults. At least two sedimentary discontinuities and two‐stage deformations occurred after the deposition of Cretaceous strata. Samples of magnetic fabrics from the Qionglai–Changshiba profile were characterized by the triaxial magnetic susceptibility ellipsoids common in sedimentary rocks. The magnetic fabrics of the profile represent a weak deformation that was associated with layer‐parallel shortening before folding and mainly reflect the Mesozoic–Cenozoic NW–SE convergence. There are also the following atypical magnetic fabrics: magnetic foliation that is oblique to the bedding and that was associated with layer‐parallel simple shearing during folding; and magnetic lineation that is to varying degrees oblique to the strike of bedding and represents a superposition of structures. Based on the correlation results of magnetic fabrics for samples of different ages, a tectonic superposition since the Late Indosinian Orogeny was found in FBSL. By combining field structural analysis and magnetic fabrics, it was suggested herein that the FBSL is a propagation product of Mesozoic–Cenozoic deformations of southern LMS to the southeast, which therefore experienced a composite superposition of deformations. This finding provides the basis for a comprehensive understanding of the southern LMS and may shed light on the uplift of the eastern margin of the Tibetan Plateau and the tectonic response of its eastern boundary.