The aim of this work is to expand the list of possible applications of microseismic data and use it for reflection imaging. Microseismic events are considered as an analogue of active seismic sources and the corresponding wavefield is treated as seismic reflection data. In this thesis a special method is developed that takes the specific character of microseismic waveforms into account and allows its use this wavefield for the imaging of seismically active zones.The first question one has to answer is whether any reflected waves are presented in the microseismic recordings. To check this, a new algorithm for grouping and sorting seismograms is proposed. The produced seismic data gathers show that in many cases microseismic waveforms contain coherent signals that can be associated with reflections. Low energy and the complicated radiation patterns of microseismic sources as well as the usually restricted data aperture, make the application of conventional imaging techniques problematic. The Microseismic Reflection Imaging method employs the directional migration approach called “Fresnel Volume Migration”. It strongly reduces the imaging artefacts caused by the low aperture of the data, but it requires the estimation of the polarity of the wavefield. Unfortunately, the exact calculation of the polarisation is not always possible for weak microseismic signals. The proposed method uses a hodogram analysis to identify the parts of the recordings for which one can get a reliable polarisation. Only these parts are then used for imaging, while the rest of the data are automatically excluded. The method takes advantage of the unique properties of microseismic data, such as location of the microseismic sources directly inside the area of interest and the high frequency of reflection data. This allows one to get images of small-scale heterogeneities in a seismically active zone or stimulated reservoir.The Microseismic Reflection Method is applied to both natural and induced seismicity data sets with various data qualities and acquisition geometries. The application results show the potential of microseismic waveform data for seismic reflection imaging. Migrated microseismic reflection data can provide information about the internal structure of a seismically active zone or a stimulated reservoir. Moreover, the presented method helps to observe the features of a seismically active area that are not visible to other methods.
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