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  • 1
    Electronic Resource
    Electronic Resource
    First results from the Reykjanes Ridge Iceland Seismic Project 1977 (1979)
    [s.l.] : Nature Publishing Group
    Nature 279 (1979), S. 56-60 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The experiment described here was a joint land-sea project with a number of shotpoints on sea and land giving a set of reversed and overlapping profile segments and large observational distances. Figure 1 shows positions of shots and receivers. Nineteen shots with charges from 0.4 to 4.0 tons were ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/279056a0
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    3-D Prestack-migration of Wide-angle Data from a Variscan Transition Zone (1999)
    Springer
    Pure and applied geophysics 156 (1999), S. 173-186 
    Details
    ISSN: 1420-9136
    Keywords: Key Words: Variscan basement, 3-D wide-angle data, DEKORP, deep seismic sounding, crustal structure, prestack-migration.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —In addition to the near normal-incidence observations within the German DEKORP 2 project in 1984, wide-angle observations have been carried out on a parallel profile across the boundary between the Saxothuringian and Moldanubian crust, approximately 50 km NE of the main transect to control three-dimensional variations. Explosion sources have been used for the entire survey, providing excellent conditions for wide-angle registrations. A velocity model has been derived on the basis of in- and off-line refraction measurements using a kinematic raytracer which was extended to three dimensions by interpolation of 2-D velocity fields between parallel sections. Although prestack-migration of the data led to aliasing effects due to large shot and geophone spacing, stable results were obtained by forming envelopes after single-shot migration. The migrated sections reveal a strongly reflective Moho at about 31 km depth and a steeply (50°) dipping intracrustal reflector, which seems to be related to the border between the two Variscan units.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050295
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Focusing in Prestack Isochrone Migration Using Instantaneous Slowness Information (1999)
    Springer
    Pure and applied geophysics 156 (1999), S. 187-206 
    Details
    ISSN: 1420-9136
    Keywords: Key Words: Prestack migration, instantaneous slowness, migration artefact, crystalline crust, DEKORP.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —Prestack migration finds increasing application in processing crustal seismic data. However, less effort has been made to incorporate slowness information in the imaging process. The combination of slowness information with migration leads to an improved image in the depth domain, especially by reducing migration artefacts and noise. A slowness-driven isochrone migration scheme is introduced for migration of 2-D seismic data. Instantaneous slowness information p(x, t) is extracted from the data using correlation analysis in moving time and space windows. Slowness values resulting from spatial coherent energy (signal) and incoherent background noise are distinguished by the simultaneous evaluation of an instantaneous coherence criterion g(x, t). In slowness-driven isochrone migration this information is used for locally weighting the amplitude A(x, t) smearing on the isochrone surface. In particular, slowness p and coherence criterion g determine position and sharpness of a Gaussian weighting function. The method is demonstrated using two synthetic data examples and is subsequently applied to two deep crustal data sets, one wide-angle (along DEKORP4) and one steep-angle reflection seismic observation (KTB8506). Both data sets were collected in the surroundings of the KTB drill site, Oberpfalz, as part of the German DEKORP project.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050296
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Recent investigations of surficial and deeper crustal structures of the Eastern and Southern Alps (1972)
    Springer
    International journal of earth sciences 61 (1972), S. 349-395 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract After a review of the surficial structures of the Eastern and Southern Alps a discussion of some important theories of the Alpidic Orogeny is presented. Geological cross sections, based as far as possible on the latest data, are then presented in detail. In the geophysical part the most important results of seismic, gravimetric and magnetic work have been compiled. Two vertical profiles through the earth's crust are presented showing lines of equal velocity of longitudinal waves.
    Abstract: Résumé Après avoir donné un aperçu sur les structures de surface des Alpes Orientales et Méridionales, les auteurs discutent quelques hypothèses importantes sur la formation alpidique des montagnes. Une description de profiles géologiques esquissés d'après les connaissances d'aujourd'hui suit cette discussion. Le chapitre sur la géophysique résume les résultats de levées sismiques, gravimétriques et magnétiques les plus importants. Deux coupes verticales à travers la croûte terrestre démontrent les lignes de vélocité égale des ondes longitudinales.
    Notes: Zusammenfassung Nach einem Überblick über die Oberflächenstrukturen der Ost- und Südalpen werden einige wichtige Theorien über die alpidische Gebirgsbildung besprochen. Es folgt eine Beschreibung geologischer Profile, die nach dem derzeitigen Kenntnisstand entworfen wurden. Im geophysikalischen Teil werden die wichtigsten Ergebnisse seismischer, gravimetrischer und magnetischer Untersuchungen zusammengefaßt. In zwei Vertikalschnitten durch die Erdkruste werden die Linien gleicher Geschwindigkeit der Longitudinalwellen dargestellt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01896323
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Physical parameters measured on cores and cuttings from the pilot well (0 m–4000.1 m) of the German continental deep drilling program (KTB) in the Oberfalz area, Bavaria, Federal Republic of Germany (1992)
    Springer
    Surveys in geophysics 13 (1992), S. 1-34 
    Details
    ISSN: 1573-0956
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The project of an ultradeep drill hole (KTB) in the Oberpfalz area at the western margin of the Bohemian Massif has completed a pilot drill hole to a depth of 4000.1 m in April 1989. This well is situated only about 200m away from the main drill hole aimed at 10 km depth where drilling started in September 1990. The cores of the pilot well have a diameter of 9.4 cm or 10.16 cm, respectively. In addition to cores and cuttings there was also mud available for geochemical, petrological and some geophysical measurements. The pilot drill hole has a core recovery length of as much as 3042.6 m (about 76%), among which 193.1 m were obtained by rotary drilling and 2849.5 m by wireline drilling. Several petrophysical parameters were measured in a specially established field laboratory at the drill site immediately after sampling in order to obtain as good as possible in-situ values. Results for the following parameters are reported: density, natural gamma ray activity, velocities of seismic longitudinal and shear waves, thermal conductivity, electrical resistivity, natural remanent magnetization, magnetic susceptibility, porosity and inner surface. The methods of measurement are characterized briefly and the results of the pilot drill hole are presented and discussed in connection with the lithology and the geophysical anomalies, which have been observed on the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901949
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    Paper (German National Licenses)
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  • 6
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    Deep Vertical Seismic-/Multi source Point-Profiling (VSP/MSP) at the KTB Deep Crustal Lab (1998)
    In:  Evaluierung
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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  • 7
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    Seismic Velocity and Anisotropy Measured in Situ until 8550 m Depth at the KTB Deep Drillhole (Oberpfalz, South Germany) (2001)
    In:  EGS XXVI. General Assembly
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/conferenceObject
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  • 8
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    Crustal structure of the Eastern Alps along the TRANSALP profile from wide-angle seismic tomography (2006)
    In:  Tectonophysics
    Details
    Publication Date: 2020-02-12
    Description: The objective of the TRANSALP project is an investigation of the Eastern Alps with regard to their deep structure and dynamic evolution. The core of the project is a 340-km-long seismic profile at 12°E between Munich and Venice. This paper deals with the P-wave velocity distribution as derived from active source travel time tomography. Our database consists of Vibroseis and explosion seismic travel times recorded at up to 100 seismological stations distributed in a 30-km-wide corridor along the profile. In order to derive a velocity and reflector model, we simultaneously inverted refractions and reflections using a derivative of a damped least squares approach for local earthquake tomography. 8000 travel time picks from dense Vibroseis recordings provide the basis for high resolution in the upper crust. Explosion seismic wide-angle reflection travel times constrain both deeper crustal velocities and structure of the crust–mantle boundary with low resolution. In the resulting model, the Adriatic crust shows significantly higher P-wave velocities than the European crust. The European Moho is dipping south at an angle of 7°. The Adriatic Moho dips north with a gentle inclination at shallower depths. This geometry suggests S-directed subduction. Azimuthal variations of the first-break velocities as well as observations of shear wave splitting reveal strong anisotropy in the Tauern Window. We explain this finding by foliations and laminations generated by lateral extrusion. Based on the P-wave model we also localized almost 100 local earthquakes recorded during the 2-month acquisition campaign in 1999. Seismicity patterns in the North seem related to the Inn valley shear zone, and to thrusting of Austroalpine units over European basement. The alignment of deep seismicity in the Trento-Vicenza region with the top of the Adriatic lower crust corroborates the suggestion of a deep thrust fault in the Southern Alps.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 9
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    Seismicity and stress field in the vicinity of the KTB location (1997)
    In:  Journal of Geophysical Research
    Details
    Publication Date: 2020-02-12
    Description: A local, broadband, seismic network of four observatory-quality stations (KTB-NET) was operated during the drilling of the KTB hole, within the framework of the interdisciplinary German Continental Deep Drilling Program (KTB). The aim was to investigate the seismic activity with regard to the tectonic stress field and to compare it with data from in situ measurements in the 9.1-km deep borehole sections (bottom temperature of 260°C and heat flow of 82–85 mW/m2). From October 1990 to November 1995, over 80 local microearthquakes with magnitudes from 0.2 to 2.8 ML were recorded: eight small events by the KTB-NET only and four earthquake swarms with 73 events by the KTB-NET and stations of the Vogtland/Western Bohemia networks. Six of the small events are located within or close to the KTB-NET. The swarm events occurred at the southwestern extension of the Ohre rift, in an area 20 km north of the drill site, which is revealed to be part of the Vogtland/Western Bohemia seismotectonic unit, characterized by swarm activity. The hypocenters are limited to the upper 13 km of the crust, with a distinct concentration between 10 and 12 km. All types of fault plane solutions are found, but at depths greater than 8 km, reversed faulting mechanisms predominate. P axes are very uniformly oriented in a NNW-SSE direction, corresponding to the well-known regional stress orientation in central Europe and in agreement with the special in situ stress measurements of the KTB program. The focal mechanism of a ML=1.2 event induced by a fluid injection experiment fits into the results obtained from the natural events. Possible indications for the brittle-ductile transition are discussed in view of the observed earthquake depth and focal mechanism distributions.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 10
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    Origin and nature of crystal reflections : results from integrated seismic measurements at the KTB superdeep drilling site (1997)
    In:  Journal of Geophysical Research
    Details
    Publication Date: 2020-02-12
    Description: For almost 10 years the KTB superdeep drilling project has offered an excellent field laboratory for adapting seismic techniques to crystalline environments and for testing new ideas for interpreting seismic reflections in terms of lithological or textural properties of metamorphic rock units. The seismic investigations culminated in a three-dimensional (3-D) reflection survey on a 19 × 19 km area with the drill site at its center. Interpretation of these data resulted in a detailed, structural model of the German Continental Deep Drilling Program (KTB) location with dominant, steep faults in the upper crust. The 3-D reflection survey was part of a suite of seismic experiments, ranging from wide-angle reflection and refraction profiles to standard vertical seismic profiles (VSP) and more sophisticated surface-to-borehole observations. It was predicted that the drill bit would meet the most prominent, steeply dipping, crustal reflector at a depth of about 6500–7000 m, and indeed, the borehole penetrated a major fault zone in the depth interval between 6850 and 7300 m. This reflector offered the rare opportunity to relate logging results, reflective properties, and geology to observed and modeled data. Post-Variscan thrusting caused cataclastic deformation, with partial, strong alterations within a steeply dipping reverse fault zone. This process generated impedance contrasts within the fault zone on a lateral scale large enough to cause seismic reflections. This was confirmed by borehole measurements along the whole 9.1 km deep KTB profile. The strongest, reflected signals originated from fluid-filled fractures and cataclastic fracture zones rather than from lithological boundaries (i.e., first-order discontinuities between different rock types) or from texture- and/or foliation-induced anisotropy. During the interpretation of seismic data at KTB several lessons were learned: Conventional processing of two-dimensional (2-D) reflection data from a presite survey showed predominantly subhorizontal layering in the upper crust with reflectivity striking in the Variscan direction. Drilling, however, revealed that all rock units are steeply dipping. This confirms that surface common depth point (CDP) seismics strongly enhances subhorizontal reflectivity and may thus produce a very misleading crustal image. Although this was shown for synthetic examples earlier, the KTB provides the experimental proof of how crucial this insight can be.
    Language: English
    Type: info:eu-repo/semantics/article
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