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Three‐dimensional focused seismic imaging for geothermal exploration in crystalline rock near Schneeberg, Germany
Author(s) -
Hloušek Felix,
Hellwig Olaf,
Buske Stefan
Publication year - 2015
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12239
Subject(s) - seismic vibrator , geology , seismology , syncline , fault (geology) , geophysical imaging , geothermal gradient , seismic survey , echelon formation , geological survey , geophysical survey , tectonics , paleontology , geophysics
We present the results of a 3D seismic survey acquired near the city of Schneeberg in the western Erzgebirge (Germany). The main objective of this survey was to use reflection seismic exploration methods to image a major fault zone in crystalline rock, which could serve as a geothermal reservoir at a target depth of about 5 km–6 km with expected temperatures between 160°C–180°C. For this purpose, a high‐resolution 3D Vibroseis survey was performed in late 2012 covering an area of about 10 km × 12 km. The 3D survey was complemented by a wide‐angle seismic survey for obtaining velocity information from greater depths using explosives along ten profile lines radially centred at the target area. The region itself is dominated by the northwest‐southeast striking Gera‐Jáchymov fault system and the southwest–northeast striking Lössnitz–Zwönitz syncline. The main geological features in the survey area are well known from intensive mining activities down to a depth of about 2 km. The seismic investigations aimed at imaging the partly steeply dipping fault branches at greater depths, in particular a dominant steeply northeast dipping fault (Roter Kamm) in the central part of the survey area. In addition to this main structure, the Gera–Jáchymov fault zone consists of a series of steeply southwest dipping conjugate faults. For imaging these structures, we used a focusing pre‐stack depth migration technique, where the wavefield coherency at neighbouring receivers is used for weighting the amplitudes during migration. This method delivers a clear, focused image of the 3D structures within the target area. A 3D velocity model for depth imaging was obtained by first‐arrival tomography of the wide‐angle survey data. With this approach, we were able to image several pronounced structures interpreted as faults within the crystalline rock units, which partly reach the target depth where the temperatures for a geothermal usage would be sufficient. In general, the results show a complex three‐dimensional image of the geological structures with different reflection characteristics, which can serve as a basis for a detailed characterization of the potential deep geothermal reservoir.