Schreiter, Lena, Hlousek, Felix, Hellwig, Olaf and Buske, Stefan (2015) Characterization of seismic reflections from faults in a crystalline environment, Schneeberg, Germany: Seismic reflections from faults. Geophysical Prospecting, 63 (4). pp. 1015-1032. DOI 10.1111/1365-2478.12255.

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Abstract

We present an approach for analysing seismic reflections from faults in a crystalline hard rock environment. We analysed 3D seismic reflection data for geothermal reservoir characterization acquired in the Erzgebirge Region, Germany. The seismic image derived from this data set revealed two main features: a less pronounced reflector corresponding to a steeply dipping major fault zone Roter Kamm and a group of pronounced reflectors attributed to the existence of conjugate mineralized faults. We analysed these reflections in the pre‐stack data to characterize the nature and origin of reflectivity. This was done by extracting the corresponding waveforms from the raw data and carefully pre‐processing them, including amplitude correction for geometrical spreading and signal‐to‐noise enhancement. Reflection coefficients were derived from the pre‐processed shot gathers by comparing the amplitudes of the reflected and direct waves. Synthetic waveform modelling using the reflectivity method has been performed for several model families consisting of one‐dimensional velocity–depth functions with varying velocities, densities, and thicknesses of the layers. A comparison of the modelled and observed waveforms revealed that a reflection coefficient of 0.18 for the conjugate mineralized faults can be explained by single layers with high impedance contrast and a thickness between 30 m and 40 m, whereas the reflection from the Roter Kamm fault zone with a reflection coefficient of −0.23 requires a model consisting of several low‐velocity layers with a total thickness of up to 100 m embedded in a high‐velocity background model. These results are in accordance with the geological interpretation of these reflectors. However, the characteristics of these reflections vary significantly within the investigation area, both in terms of the reflection coefficient and the waveform, which is also in agreement with the general lateral variation of fault zone characteristics known from tectonic investigations such as geological mapping of outcrops and fabric analysis.

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