The Inversion Of Slip-rate On Qilianshan Fault Through Chaos-genetic Algorithm

To inverse fault slip and rotation from geodetic observation data is the most essential andimportant method in crust deformation research, earthquake mechanism exploration and top-ographicalevents explanation. The current thesis will combine the GPS data with thedislocation model, using the Chaos-Genetic Algorithm to inverse the slip rate of Qilianshanfault, locating in the Northeast Margin of Tibet Plateau. Main work and conclusions are asfollows:1. Discusses the mathematical theory of inverse and the fault activity model, thus givingthe mathematics analytic expressions of the fault activity model.2. Analyzes the advantages and disadvantages of Genetic Algorithm, introduces in theChaos optimization theory, then intelligent integrates it with Genetic Algorithm to developChaos-Genetic Algorithm. The results of function test show that the algorithm convergence isbetter than the Simple Genetic Algorithm in both the rate of convergence and precision.3.-Based on GPS data collected during2001to2004, this thesis adopts Chaos-GeneticAlgorithm to inverse the Qilianshan fault slip velocity. The results show that:Besides obviouscrust shortening, left-lateral slip movement of Qilianshan fault is also remarkable. Thedistribution of this movement range is spatially uneven, and they are2mm/yr，0.4~1mm/yrand3.8~5mm/yr from west to east.4. Through comparing and analyzing the inversion result of Qilianshan fault slip rate andthe fault slip rate of GPS section, it can be concluded that their results are consistent ingeneral. This proves the feasibility of the Chaos-Genetic Algorithm to inverse the fault sliprate.5. When simulating the horizontal motion velocity field around Qilianshan based oninversion result of the Qilianshan fault slip rate, the simulating values and GPS measuredvalues are responding to each other very well. The differences are mainly embodied in thefact that GPS measured values reflect the result caused by regional fractures as a whole, whilethe simulation result only represents crust deformation caused by a single fault sliding ofQilianshan.