Application of Wavelet Multi‐Resolution in the Study of Crust‐Mantle Heterogeneous Scale

Abstract

AbstractUsing “zoom” multi‐resolution of wavelets, we developed a varying scale phase analysis method for complicated waveforms of crust‐mantle transitional zone (CMTZ), and integrated the method with the study of heterogeneous scale of CMTZ, thus transforming the conventional phase identification from “static” into “dynamic”. Relevant computer programming has been completed. With reference to Pm waveform of CMTZ along Maqin‐Lanzhou‐Jingbian profile, two continent‐continent collision zones were revealed with the complexity coefficient method. The two zones correspond to the Maqin fault and the M=8.5 Haiyuan earthquake region, respectively. The multi‐layer Pm phase under the Maqin fault and Haiyuan earthquake was obtained with the varying scale phase analysis method. The result shows that CMTZ under Haiyuan earthquake is about 20km thick, with distinguishable layers. It consists at least of 3 layers of high and low velocity alternatively, whereas CMTZ corresponding to the Maqin fault is composed of 2 thin layers. This difference in stratification and thickness shows that the contact zone between Ordos block and Qilian block differs obviously from the contact zone between Bayankar block and Chaidamu block in the present distinguishable heterogeneous scale of CMTZ, because the continent–continent collisions happened at different times and the continents interacted in different ways.