Effect of stress ratio and friction coefficient on composite P wave radiation patterns
Resource
Chinese Journal of Geophysics-Chinese Edition, 54(4), 994-1001
Journal
Chinese Journal of Geophysics-Chinese Edition
Journal Volume
54
Journal Issue
4
Pages
994--1001
Date Issued
2011
Author(s)
Abstract
In order to study the impact of stress ratio and friction coefficient on P-wave radiation patterns from a large number of earthquakes, we present how the shear stress, friction stress and Coulomb failure stress of the fault varies as a function of its orientation with respect to different stress ratios. The results show that the shear stress on the fault plane with various orientations indicates larger differences comparing to friction stress variations for different fault orientations. Assuming the spatial distribution of Coulomb failure stress is relevant to the P wave radiation pattern, and fault plane orientations are randomly distributed over the whole space, we superpose P wave radiation patterns from all fault orientations, and illustrate the characteristics of composite P wave radiation pattern in terms of different stress ratio and friction coefficient. We find that the stress ratio and friction coefficient both affect the composite P wave radiation pattern. To some extent, the shape of the composite P wave radiation can be changed by varying any of the two parameters, indicating the difficult to solve both of the parameters indepdently. However, if the friction coefficient can be determined by other methods, we can obtain a reasonable stress ratio by using P wave first motions. This work provides new idea to accurately determine stress field considering friction coefficient by large number of P first motion polarity data.
Type
journal article