In 1998, two wide‐angle reflection and refraction profiles were carried out around Jiashi area at the northeast side of the Pamirs and its adjacent area. The results show that obvious differences of crustal structures exist in West Kunlun Mountains, Tarim basin, and Tianshan Mountains. Tarim block has the crustal structure features of a stable block, its average crustal velocity is relatively high (6.5 km/s). Southwards intoWest Kunlun Mountains, the crust thickens distinctly, the thickness is about 70 km, its average crustal velocity is lower (6.0–6.2 km/s), and this low average crustal velocity mainly results from relatively low velocity of the lower crust. It implies special features of the lower crust medium in West Kunlun fold zone. Northwards into Tianshan fold region, the crust also thickens, but the extent of thickening is weaker, the thickness of the crust is about 50–55 km. The Tianshan Mountains are also characterized by low crustal velocity (6.2 km/s). It implies that the crust of Tianshan Mountains is relatively “soft”. But the low average crustal velocity of Tianshan block results from both lower crust and middle crust, where low velocity is distributed widely. Under strong compressional actions of India plate, the crust of this area has undergone inhomogeneous deformation and the Tarim block interpolates beneath the West Kunlun and Tianshan blocks in south and north directions respectively, which formed a deep tectonic setting for frequent occurrence of strong earthquakes in this area.

The extended finite element method (XFEM) is a new numerical method for modeling discontinuity. Research about numerical modeling for concrete hydraulic fracturing by XFEM is explored. By building the virtual work principle of the fracture problem considering water pressure on the crack surface, the governing equations of XFEM for hydraulic fracture modeling are derived. Implementation of the XFEM for hydraulic fracturing is presented. Finally, the method is verified by two examples and the advantages of the XFEM for hydraulic fracturing analysis are displayed. extended finite element method (XFEM), hydraulic fracture, concrete, numerical modeling

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Damage in a structure alters its dynamic characteristics. Significant research has been conducted in damage detection and structural health monitoring using dynamics-based techniques. But simultaneously determining the presence, severity, and location of damage using the existing damage detection methods can still prove challenging. In this study, a new practical method of structural damage detection called Local Damage Factor (LDF) is presented, which is capable of determining the presence, severity, and location of structural damage at the same time. By including the dynamic characteristics of the intact local structure in the LDF method, the influence of structural nonlinearity, imperfections, and system noise is considered, so that the accuracy of damage detection is improved. Furthermore, a modified LDF (MLDF) method is proposed, which can detect damage without requiring benchmark data for the intact local structure. As a demonstration, the proposed LDF and MLDF methods are applied to damage detection in a 3-D steel frame structure, and the experimental results indicate that both methods can effectively determine the presence, severity, and location of a crack cut into one of the pillars in the frame with a saw. The LDF method is effective in a way that can eliminate both the nonlinear severity effect of structure itself and the ambient noise inherent in the intact structure, whereas the MLDF method is advantageous in that it does not require information about the intact local structure, which is often unavailable for damage detection. The proposed LDF method of in situ damage detection is illustrated using the concrete columns in a wharf structure. The successful detection of damage in the 3-D steel frame, as well as the wharf, demonstrates that the proposed local damage factor technique can be effectively and efficiently used in damage detection and structural health monitoring of structures.