Approximate Reflection Coefficients at a Fracture for Microseismic Needs

Reflection seismic data from microseismic events were recently used to image fractures and determine reservoir properties. In this context we earlier considered reflections induced by an incident plane wave at a fluid layer embedded in an elastic medium. The exact formulas are quite complex, so that for further calculations a simplification is useful. If we use quantities as they are used in microseismicity, we can expand the exact formulas and find such simplification. In this work we introduce the corresponding approximate reflection coefficients (PP, PS, SS, SP) that actually represent the exact reflection coefficients at an ideal slip interface. We have shown that the ideal slip interface is a good approximation of a fluid layer for values of parameters used in microseismicity. These results might be useful in the research related to reflections at fractures.