Publication Date:
2021-12-23
Description:
Abstract
Description:
The deep seismic reflection survey DEKORP 1-Laacher See was conducted as additional measurements in the Laacher See area in 1987 as part of the DEKORP-1 project, one main traverse of the German continental seismic reflection program. This small survey was an attempt to reveal the 3-D crustal structure in an area of the Quaternary East Eifel Volcanism and possibly find some magma chambers in the crust with high-fold near-vertical incidence vibroseis acquisition (DEKORP Research Group, 1991). The measurement consists of a 8,64 km long, multifold 2D seismic line 8701 across the Laacher See in NE-SW direction and two pseudo-3D seismic areas 8702 north of the lake and 8703 beneath the lake with one-fold coverage in each case.
Laacher See or Lake Laach is a caldera lake in the Rhineland-Palatinate, Germany, one of the volcanic centres of the East Eifel Volcanic Field. It belongs together with the West Eifel to the youngest volcanic areas in Central Europe. The caldera of the Laacher See was formed about 12 900 years ago after the volcano explosively erupted, and the remaining crust collapsed into the empty magma chamber below. The Laacher See is still considered to be an active volcano, proven by seismic activities and thermal anomalies under the lake.
The first processing of the Laacher See data was carried out at the Geophysical Institute of the CAU University Kiel in 1990. Unfortunately, these results have not been preserved or published. According to DEKORP Research Group (1991) the first processing resulted in poor data quality caused by high scattering and attenuation in the volcanic material near the surface. This reflected energy was not enough to image a magma chamber beneath the lake or any other structures. Thus, information about the structure of the Earth’s crust of the Eifel is mainly based on the deep seismic reflexion profile DEKORP 1B, running ca. 25 km to the west from the Laacher See und crossing DEKORP 1A at its northern profile end.
In recent years, deep low‐frequency (DLF) earthquakes have been detected in the Laacher See area indicating ongoing magmatic activity in the lower crust and upper mantle (Hensch et al., 2019, Dahm et al. 2020). These and other signatures suggested the reprocessing of the Laacher See data with modern methods. Thus, the 2D seismic line 8701 has been reprocessed in 2020 within the framework of the Master’s thesis by Agafonova (2020) written at the Technical University of Berlin and supervised by the GFZ Potsdam.
All reprocessed data come in SEGY trace format, the final sections additionally in PNG or PDF graphic format: as raw FF-sorted unstacked data, as preprocessed CDP-/FF-sorted unstacked data as well as poststack-time/-depth unmigrated and migrated sections. Moreover, the results of the tomographic inversion are included. Detailed information about acquisition and reprocessing parameters of line 8701 can be found in the accompanying Technical Report (Agafonova & Stiller, 2021).
The reprocessed results of the Laacher See survey 1987 can be of importance for better understanding the structure of the Eifel crust. Even though significant knowledge gaps and uncertainties exist due to the insufficient data quality, such important questions can already be discussed as:
•How complex is the structure beneath the Laacher See?
•Can the Mantle-Crust Boundary be defined at ca. 34 km depth?
•Are the strongly inclined events in the Upper Crust between 1-5 km depth parts of caldera ring-faults?
•Do the reflections between 5-7 km depth indicate boundaries of a possible magma chamber?
Description:
Other
Description:
The German Continental Seismic Reflection Program DEKORP (DEutsches KOntinentales Reflexionsseismisches Programm) was carried out between 1984 – 1999 as the German national reflection seismic program funded by the Federal Ministry of Research and Technology (BMFT), Bonn (now: the Federal Ministry of Education and Research (BMBF)). DEKORP was administrated by the former Geological Survey of Lower Saxony (NLfB), Hanover (now: the State Authority for Mining, Energy and Geology (LBEG)). In 1994 the DEKORP management was taken over by the Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences.
The aim of DEKORP was to investigate the deep crustal structure of Germany with high-resolution near-vertical incidence (mostly vibro)seismic acquisition, supplemented by wide-angle seismic and other target-oriented piggy-back experiments, all complemented by optimized methods of data processing and interpretation. The DEKORP project was closely linked with the KTB (German continental deep-drilling program) and was an equivalent to many other deep-seismic programs world-wide such as COCORP, BIRPS, LITHOPROBE, ECORS, CROP, BELCORP, IBERSEIS and many more. The DEKORP-Atlas (Meissner & Bortfeld, 1990) gives a detailed overview about most of the different campaigns and results.
In sum, the resulting DEKORP database includes approximately 40 crustal-scale 2D-seismic reflection lines covering a total of ca. 4 700 km and one 3D-seismic reflection survey covering ca. 400 km². Each DEKORP survey is provided with all datasets that are necessary for either a re-processing (i.e. raw unstacked field records in SEGY) or a re-interpretation (i.e. finally processed sections in SEGY or PNG). The raw data are sorted by records or by CDPs. The final data are available as unmigrated or migrated stacks without or with coherency enhancement. Automatical line-drawings are also included. All data come with additional meta information for each domain (source, receiver, CDP) like coordinates, elevations, locations and static corrections combined in ASCII-tables for geometry assignment. Furthermore, all metadata originating from paper copies are made available as scanned files in PNG or PDF, e.g. field and observer reports, location maps in different scales, near-surface profile headers and others.
The DEKORP datasets provide unique and deep insights into the subsurface below Germany covering the earth’s crust from the surface to the upper mantle and are increasingly requested by academic institutions and commercial companies. Fields of applications are geothermal development, hazard analysis, hydrocarbon/shale gas exploration, underground gas storage, tunnel construction and much more.
Keywords:
DEKORP
;
Deutsches Kontinentales Reflexionsseismisches Programm
;
deep crustal structure
;
crustal-scale seismic survey
;
near-vertical incidence seismic reflection
;
Vibroseis acquisition
;
Rhenish Massif
;
Varisca Orogenic Belt
;
Rhenohercynian
;
Laacher See Volcano
;
East Eifel Volcanic Field
;
deep low-frequency earthquakes
;
Mohorovičić discontinuity
;
geothermal resources
;
seismic risks
;
EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 EARTHQUAKES 〉 SEISMIC PROFILE
;
EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 PLATE TECTONICS
;
In Situ/Laboratory Instruments 〉 Profilers/Sounders 〉 SEISMIC REFLECTION PROFILERS
;
lithosphere 〉 earth's crust
Type:
Dataset
,
Dataset
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