| The Coulomb failure function (CFF) quantitatively describes stress changes in sec-ondary faults near the source fault of an earthquake. It can be employed to monitor how stress transfers and then to shed some light on the probability of successive events occurring around a source fault. Accordingly, it has become a crucial quantitative index to investigate and interpret mainshock-mainshock, mainshock-aftershock, mainshock-volcano and volcano-volcano triggering phenomena as well as communication among major active faults over the past two decades. Nevertheless, there are still some funda-mental problems which should be figured out. One is which kind of receiver fault should be chosen for the analysis of earthquake stress triggering and the other is how sensitive the CFF is to its parameters. Besides, what the characteristic of stress evolution is when coseismic, postseismic and interseismic Coulomb stresses are completely considered also should be investigated, compared with that of conventional coseismic Coulomb stress. Therefore, the aim of this dissertation is twofold:(1) setting up a general analytical Coulomb stress model and estimator of CFF; (2) exploring stress transfer among the 1997 Mw7.6 Manyi earthquake and the 2001 Mw7.8 Kokoxili earthquake and stress evolution due to coseismic, postseismic and interseismic Coulomb stress of the 2008 Wenchuan earthquake.Based on the basic philosophy of Coulomb stress that the seismogenic fault would slide if the shear stress on it overcomes its frictional force and it would unclamp if its normal stress is extensional and vice versa, I build a unified model to determine an optimally oriented plane and its corresponding Coulomb stress, then apply the model to the 2003 Mw 6.6 Bam (Iran) earthquake and the 2008 Mw 7.9 Wenchuan (China) earthquake, thereby checking its effectiveness. The results show that spatial correla-tion between positive Coulomb stress changes and aftershocks are, for the 2003 Bam earthquake,47.06% when elastic Coulomb stress changes are resolved on uniform planes and 87.53% when these are resolved on optimally oriented planes at depth; for the 2008 Wenchuan earthquake the correlations are 45.68% and 58.20%, respectively. It is recommended that account be taken of optimally oriented planes when drawing a Coulomb stress map for analyzing earthquake triggering effects between mainshock and aftershocks, in which case the source mechanisms of aftershocks are often undetermined.I next construct an error estimator of Coulomb stress model based on the unified model built previously and then systematically investigate the sensitivity of Coulomb stress model to the uncertainties of the slip distribution of source fault, the stress tensor relative to seismogenic earthquake fault, the friction coefficient of receiver fault, the strike, dip and rake of receiver fault and tectonic background stress as well as Coulomb stress model itself. The results show that:(1) The larger the standard deviation of the slip distribution of source fault inverted, the more fluctuational the spatial pattern of Coulomb stress is, especially in the vicinity of source fault, and the relative error of Coulomb stress arising from the uncertainty of stress tensor imparted by source fault is generally 90%-100%, both of which indicate that the slip distribution of source fault should be carefully constrained in order to draw a reasonable Coulomb stress map; (2) The Coulomb stress is not dramatically sensitive to the uncertainty of friction coefficient for strike-slip source fault but it is slightly affected for dip-slip and tensile source faults, implying that choosing an empirical friction coefficient is reasonable according to the secular slip history of seismogenic fault; (3) The uncertainty of the strike of receiver fault affects Coulomb stress more heavily than that of the dip of receiver fault does and for the rake of receiver fault case its effect is more trivial, and thus the strike of receiver fault should be better constrained for the analysis of Coulomb stress than the other two;(4) When the magnitude of tectonic background stress chosen is relatively smaller than those of stress induced by earthquake, both the magnitude and direction of tectonic background stress have minor role in changing the spatial pattern of Coulomb stress, whereas when the magnitude of tectonic background stress chosen is larger, say tens of times of the magnitude of earthquake stress, the direction of tectonic background stress begins to dominate the spatial pattern of Coulomb stress. Given that tectonic background stress is commonly larger than the stress induced by earthquake, the direc-tion of tectonic background stress should be carefully determined when one considers Coulomb stress on optimally oriented plane receiver fault;(5) The spatial pattern of Coulomb stress calculated with a simpler Coulomb stress model where an assumption that pore pressure is proportional to normal stress of fault exits is not dramatically different from that of Coulomb stress calculated with the Coulomb stress model without such assumption. However, the difference of the magnitude of Coulomb stress owing to this assumption is not ignorable. Therefore, the Coulomb stress model without this assumption should be employed for analysis of Coulomb stress triggering.After presenting a unified Coulomb stress model and systematically investigating the sensitivity of Coulomb stress model to its parameters and thereby bearing some creteria in mind, I explore stress transfer and stress evolution of three strong earth-quakes, the 1997 Mw7.6 Manyi earthquake, the 2001 Mw7.8 Kokoxili earthquake and the 2008 Mw7.9 Wenchuan earthquake in Tibet Plateau as case studies of Coulomb stress triggering.I examine the coupling of stress transfer among strong earthquakes in the vicinity of Kunlun fault such as 1937 M7.5 Huashixia earthquake,1963 M7.0 Doulan earthquake, 1973 M7.3 Manyi earthquake,1997 Mw7.6 Manyi earthquake,2001 Mw7.8 Kokixili earthquake and 2010 Mw6.9 Yushu earthquake with focus on stress transfer between the 1997 Mw7.6 Manyi earthquake and the 2001 Mw7.8 Kokoxili earthquake with Coulomb stress model. The result show that the occurrences of these six strong earthquakes can be interpreted with coseimsic Coulomb stress map. Nevertheless, Only 2010 Mw6.9 Yushu earthquake can be interpreted with coseismic and interseismic Coulomb stresses remarkably well, which might arise from the fact that the effect of viscoelastic relaxation of lower crust and upper mantle is not considered. Besides, the Coulomb stresses im-parted by the 1997 Mw7.6 Manyi earthquake on ruptured fault planes of the 2001 Mw7.8 Kokoxili earthquake are-0.03-0.02bars with the average being 0.002bars and most of fault planes have positive Coulomb stress, indicating that the former weakly promoted the latter; The 2001 Mw7.8 Kokoxili earthquake imparted all positive Coulomb stresses no larger than 0.08bars on the fault planes of the 1997 Mw7.6 Manyi earthquake and hence it would hasten potential earthquakes to occur on ruptured planes of the 1997 Manyi earthquake.I probe the spatial pattern of aftershocks of the 2008 Wenchuan Mw7.9 earth-quake and stress evolution due to coseimsic, postseismic and interseismic deformation on major active faults around this strong earthquake. The coseismic stress imparting from the 2008 Mw7.9 Wenchuan earthquake, postseismic stress due to postseismic re-laxation of lower crust and upper mantle and interseismic strain accumulation are now completely considered, compared with previous analysis of Coulomb stress triggering of the 2008 Mw7.9 Wenchuan earthquake. The results show that the spatiotemporal pattern of aftershocks of the 2008 Mw7.9 Wenchuan earthquake is consistent with the net Coulomb stresses remarkably well, that is, most of the aftershocks lie in zones with positive Coulomb stresses. The coseismic stresses on major faults imparted by the 2008 Mw7.9 Wenchuan earthquake is changed by time-dependent postseismic and interseis-mic Coulomb stresses and therefore complete Coulomb stresses coming from different phases such as coseismic, postseismic and interseismic ones in earthquake cycle should be considered in order to make a robust assessment of the segments of faults with po-tential earthquake hazard. The net Coulomb stress map shows that Yushu-Maqu fault, Xianshuihe fault, Anninghe fault, Zemuhe fault, Daliangshan fault, the eastern Kunlun fault and Haiyuan fault are all gradually being loaded with positive Coulomb stresses and pose earthquake hazards in future.
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