Receiver Functions From Freauency Domain With Single Event To Calculate Crustal Thickness And Poisson’s Ratio In Yunnan

Receiver functions is currently a popular and powerful tool to study the crust and upper mantle. The principle is to transform the complicated teleseismic body waves to the pulses such that the arrival time of converted waves becomes easy to accurately recognize. In the mathematical sense, the receiver functions are similar to the Green’s function. However, most of the programs of receiver functions are introduced from abroad. One of the most important motivation of this thesis to build and test a program of receiver functions in the frequency domain by ourselves and independently.From the application prospective, most are focused on superposition of multiple events and few employ a single event for computation of receiver functions. The superposition of multiple events is advantageous in that undesired interference and noise can be removed, but has to employ a reference Earth model for moveout correction. Because the reference Earth model may not well represent the actual model in the region under investigation, the moveout correction may have error which further results in the inaccuracy of the superposed (final) trace. For this reason, this study attempts to use the approach of a single event, and the associated disadvantage is the possible difficulty in identifying of the converted phases.Yunnan is located on the southeast side of Tibet Plateau and the east side of Tethys Ocean, with strong seismicity and complex geological setting. In nature it is an ideal experimental field to study continental collisions. We use the receiver functions to get the crustal thickness and Poisson’s ratio in this region. The results show that the Moho depth is well correlated with the altitude of the ground surface, presenting a feature of being thick in the north and shallow in the south. This can be well interpreted using the isostatic theory. The three volcano areas in Yunnan have high Poisson’s ratio, which is reasonable in physics. The area in contact with Sichuan Basin has low Poisson’s ratio. Along the Honghe Fault there are three zones having high Poisson’s ratio, indicating that the fault has rheological behavior.