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Li Y.,Chengdu University of Technology | Zhou R.,Institute of Earthquake Engineering | Zhao G.,Chengdu University of Technology | Li H.,Chinese Academy of Geological Sciences | And 6 more authors.
Quaternary International

Many uncertainties need to be taken into account to estimate the relationship between tectonic uplift, the landslide volume triggered by the Wenchuan earthquake, and constraints on the orogenic growth of the Longmen Shan (Mountain). In this research, coseismic tectonic uplift, landslides, and postseismic debris-flows in Hongchun Gully located at the earthquake epicenter have been studied. Field data, aerial photographs, and digital elevation data were used to estimate the quantitative relationship between the tectonic uplift and landslides, debris-flows and their constraints on the orogenic growth of the Longmen Mountains. The coseismic tectonic uplift volume (667×104m3) was more than the coseismic landslide volume (380.01×104m3). Only 57% of the volume of the tectonic uplift has been converted to the volume of landslides in Hongchun Gully, indicating new uplift and orogenic growth of the Longmen Shan. The volume of postseismic debris flows was 70.5×104m3, indicating that 20% of the volume of coseismic landslides was converted into postseismic debris flows by heavy rainfall. The volume of materials discharged by Minjiang River (the main river) is 48.5×104m3, indicating that only 13% of coseismic landslide sediments has been removed from the range by fluvial processes, and at least 86% of landslide sediments still remain in the Hongchun Gully. Coseismic tectonic uplift volume exceeds coseismic landslides volume, and the Wenchuan Earthquake caused new uplift and geomorphic growth of the Longmen Mountains. This is not consistent with a previous conclusion that mass wasting triggered by the 2008 Wenchuan earthquake exceeds orogenic growth and led to a net material deficit in the Longmen Shan region. © 2014 Elsevier Ltd and INQUA. Source

Li Y.,Chengdu University of Technology | Li H.,Chinese Academy of Geological Sciences | Zhou R.,Institute of Earthquake Engineering | Su D.,Chinese Academy of Geological Sciences | And 2 more authors.

Longmen Shan is located at the boundary between the Sichuan Basin and Tibetan Plateau, representing the steepest gradient of any edges of the plateau. Three endmember models of uplift process and mechanism have been proposed, including crustal thickening, crustal flow, and crustal isostatic rebound. Here, we use tectonostratigraphic units in the Late Triassic foreland basin to restraint uplift process and mechanism in the Longmen Shan during Indosinian orogeny. The Late Triassic foreland basin developed as a flexural foredeep on the Yangtze passive continental margin during the Indosinian orogeny. The basin fill includes the Maantang Formation, the Xiaotangzi Formation and the Xujiahe Formation, and it is divided into four tectonostratigraphic units with wedge-shaped or tabular cross-sectional geometry by unconformities and flooding surfaces in this paper. The first and third ones are wedge-shaped tectonostratigraphic units and correspond to underfilled condition with basal unconformities or major flooding surfaces, the high rate of subsidence and sediment accumulation, coarsening-upward succession and a dual sediment supply, and them may link to strong active thrust loading events or the rapidly advance rate of the orogenic wedge; the second and fourth ones are tabular tectonostratigraphic units and correspond to overfilled condition with the unconformity, the low rate of subsidence and sediment accumulation, fining-upward succession, a single sediment supply, the mass emergence of conglomerate layers, and they may be related to isostatic rebound and erosion unloading. Two endmember models of uplift process and mechanism in the Longmen Shan during Indosinian cycle have been proposed by coeval Late Triassic sedimentary sequences in the foreland basin here: (1) crustal thickening during the wedge-shaped tectonostratigraphic units, (2) crustal isostatic rebound during the tabular tectonostratigraphic units. This two endmember models proposed in this paper may be helpful to understand the mechanism of the Wenchuan Earthquake. © 2013 Elsevier B.V. Source

Yu R.-F.,China Earthquake Administration | Zhou X.-Y.,Beijing University of Technology | Yuan M.-Q.,Institute of Earthquake Engineering
Structural Engineering and Mechanics

For generally damped linear systems with repeated eigenvalues and defective eigenvectors, this study provides a decomposition method based on residue matrix, which is suitable for engineering applications. Based on this method, a hybrid approach is presented, incorporating the merits of the modal superposition method and the residue matrix decomposition method, which does not need to consider the defective characteristics of the eigenvectors corresponding to repeated eigenvalues. The method derived in this study has clear physical concepts and is easily to be understood and mastered by engineering designers. Furthermore, this study analyzes the applicability of step-by-step methods, including the Newmark beta and Runge-Kutta methods for dynamic response calculation of defective systems. Finally, the implementation procedure of the proposed hybrid approach is illustrated by analyzing numerical examples, and the correctness and the effectiveness of the formula are judged by comparing the results obtained from the different methods. Source

Li Y.,Chengdu University of Technology | Zhou R.-J.,Institute of Earthquake Engineering | Zhao G.-H.,Chengdu University of Technology | Su D.-C.,Chinese Academy of Geological Sciences | And 3 more authors.
Journal of Chengdu University of Technology (Science and Technology Edition)

The tectonic pattern of the Longmenshan mainly is detachment and napping. With apparent seismic activities in recent five years, the Wenchuan (Ms 8. 0) earthquake and the Lushan (Ms 7. 0) earthquake occurred in the Longmenshan Mountains and its front in 2008 and 2013, respectively. Based on the focal mechanism solution, rupture process, seismic intensity, surface deformation, aftershocks of the Lushan earthquake and active faults on the southern segment of the Longmenshan, the authors divide the southern segment of the Longmenshan and its front into two tectonic deformation belts including the Longmenshan thrusting belt and the frontal propagation belt in this paper. By comparing the differences of tectonic deformation style, active faults and history earthquake between the two belts, the authors put forward two kinds of seismotectonic models. One is the thrusting belt characterized by the napping and detachment and another is the frontal propagation belt characterized by thrusting and detachment folding. By analyzing the seismogenic mechanism of thrusting and detachment folding in the frontal propagation belt during the Lushan earthquake, the authors consider that the Lushan earthquake formed by thrusting and detachment folding in the frontal propagation belt of the Longmenshan. The seismogenic fault of the Lushan earthquake is the Dayi fault, which dips to NW with listric surface and conver over the detachment surface. The detachment surface is just the seismic source layer of the Lushan earthquake. Source

Yu R.,China Earthquake Administration | Yuan M.,China Earthquake Administration | Yuan M.,Institute of Earthquake Engineering | Yu Y.,China Earthquake Administration
Applied Mechanics and Materials

The U.S. Geological Survey Parkfield Dense Seismograph Array (UPSAR) successfully recorded strong motions during 2003 San Simeon earthquake (M 6.5) and 2004 Parkfield earthquake (M 6.0). Because the array covers a very small area (0.45km 2), these data offer some interesting insights into spatial variations of seismic ground motions that suits for engineering scale. in this research, we study the spatial coherency function of seismic ground motion in the horizontal and vertical directions by digital signal processing. The results show that when the circular frequency is smaller than π, the degressive trend of the coherency function becomes significant with the separation distance elongation, while the data deviation of the coherency function becomes larger with the frequency rise, which shows no obvious rules. in addition, based on the strong-motion data, a suitable spatial coherency model of ground motion is selected through comparing existing model functions, and the appropriate recommendations for improvement is put forward. Finally, according to different frequency range, the fitting parameters of the spatial coherency function of ground motion are obtained through numerical simulation. The spatial coherency function proposed in this paper is practical in simulation of ground motion field. © (2011) Trans Tech Publications. Source

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