ALBERT

Description: Die vorliegende Ausgabe des GFZ-Journals „System Erde“ soll einen Einblick in die am GFZ betriebene Forschung zur Seismologie geben.

Description: Diese Ausgabe des GFZ-Journals „System Erde“ wurde im Dezember 2016 produziert und erscheint im Januar 2017. Das ist der Monat, in dem das Deutsche GeoForschungsZentrum seinen 25. Geburtstag feiert. Der Schwerpunkt Südamerika ist dabei durchaus passend, denn die Forscherinnen und Forscher des GFZ arbeiten dort seit der Gründung des Zentrums. Die Südpazifikküste mit den großen Subduktionsbeben, die Anden mit ihren Vulkanen und all die geologischen Prozesse, die in der Region sichtbar werden, sind wie die Seiten eines Lehrbuchs der Geologie – wenn man sie denn zu entziffern weiß. Selbst die so genannten passiven Kontinentalränder an den Küsten des Südatlantiks bieten uns tiefe Einblicke in die Erdgeschichte; sie sind Geoarchive erster Ordnung. Hinzu kommt, dass sie Lagerstätten für Rohstoffe bergen.

Description: Film 7: "Die Stilllegung eines CO2-Speichers – Pilotstandort Ketzin" (Länge 10:39) Produktionsjahr: 2015

Description: Very long baseline interferometry (VLBI) is one of the fundamental space geodetic techniques. Important goals for the next generation of VLBI technology are continuous operations as well as automated data processing. For this reason, it is necessary to introduce real time capable parameter estimation algorithms, such as Kalman filters, to VLBI data analysis. In this study, such a filter was implemented in the VLBI software VieVS@GFZ, and several aspects related to VLBI data processing were investigated. Within the corresponding module VIE_KAL it is possible, for example, to estimate all parameters important in VLBI analysis, adapt their stochastic models, flexibly define the datum, integrate external data, as well as extract datum free normal equations. The foci of the investigations were on the effects of the troposphere, the most important error source in VLBI analysis, and on the determination of station positions, which are of great importance in geodesy. For the stochastic model of the tropospheric delays, station- and timedependent differences were considered. In comparisons with tropospheric parameters from GNSS, water vapor radiometers and numerical weather models, the Kalman filter solution yielded 5 to 15% smaller differences than a least squares solution based on the same models and VLBI data. Also in the case of estimated station coordinates, the Kalman filter solution exhibited better baseline length and station coordinate repeatabilities. The application of station-based process noise led to additional improvements. Furthermore, the Kalman filter was used to estimate subdaily station coordinate variations caused by tidal and loading effects. Finally, the findings were used to determine Kalman-filter-based global terrestrial reference frames (TRFs). For the stochastic model of the coordinate variations of particular stations, loading deformation time series were utilized. The non-deterministic approach of the Kalman filter allowed the consideration of non-linear station movement, for example, due to irregular seasonal effects or post-seismic deformations. In comparisons with a VLBI TRF solution from a classical adjustment and ITRF2008, a good agreement in terms of transformation parameters and station velocities was achieved. The findings from testing different options related to the parameterization and to the stochastic model will help to improve future reference frames.

Description: The Eifel is the youngest volcanic area of Central Europe. The last eruption occurred approximately 11000 years ago. Little is known about the deep origin and the mechanism responsible for the Eifel volcanic activity. Earthquake activity indicates that the Eifel is one of the most geodynamically active areas of Central Europe. In this work the receiver function method is used to investigate the upper mantle structure beneath the Eifel. Data from 96 teleseismic events (mb 〉 5.2) that were recorded by both permanent stations and a temporary network of 33 broadband and 129 short period stations had been analyzed. The temporary network was operating from November 1997 till June 1998 and covered an area of approximately 400x250 km^2 centered on the Eifel volcanic fields. The receiver function analysis reveals a clear image of the Moho and the mantle discontinuities at 410 km and 660 km depth. Average Moho depth is approximately 30 km and it shows little variation over the extent of the network. The observed variations of converted waveforms are possibly caused by lateral variations in crustal structure, which could not resolved by it receiver functions}. Inversions of data and migrated it receiver functions} from stations of the central Eifel array suggest that a low velocity zone is present at about 60 to 90 km depth in the western Eifel region. There are also indications for a high velocity zone around 200 km depth, perhaps caused by dehydration of the rising plume material. The results suggest that P-to-S conversions from the 410-km discontinuity arrive later than in the IASP91 reference model. The migrated data show a depression of the 410 km discontinuity of about 20 km, which correspond to an increase of temperature of about 140° Celsius. The 660 km discontinuity seems to be unaffected. This indicates that no mantel material rises up from directly below the 660 km discontinuity in the Eifel region or the Eifel-Plume has its origin within the transition zone.

Description: Der Scientific Technical Report (STR) 03/08 ist die teilweise überarbeitete Diplomarbeit des Autors, welche im November 2002 am Lehrstuhl für Astronomie des Instituts für Planetare Geodäsie der Fakultät Forst-, Geo- und Hydrowissenschaften an der Technischen Universität Dresden eingereicht wurde.

Description: The work contained in this thesis considers deformations of the Earth, which are produced by the loads of the last ice-age glacial sheets. The forces the Earth sets against the surface loads are the buoyancy force of the Earth's mantle and the opposing force by the elastic flexure of the lithosphere. Because the time scale of the ice-age of some 100,000 years is short with respect to geological time scales, the viscoelastic behaviour of the Earth has to be considered. Viscoelasticity results in a retarded response of the Earth, which is observed as postglacial uplift in previously glaciated regions, 8,000 years after deglaciation. To model the buoyancy of the Earth's mantle, often a viscous incompressible fluid of homogeneous density is assumed. More recent studies consider also compressibility of the mantle material, but keep the homogeneous density. This results in an inconsistent reference state, because the self compression due to hydrostatic pressure is neglected. These models are discussed here, and the problems are shown, which arise from the description of the field equations for a viscoelastic compressible gravitating continuum in a half-space geometry. The opposing force by the elastic flexure of the lithosphere is determined by the flexural rigidity of the lithospheric plate. If we consider viscoelastic layers in the lithosphere, the flexural rigidity is reduced. Therefore, the overall thickness of a viscoelastic layered lithosphere is much larger than its effective elastic thickness deduced from assuming one elastic plate. Consequently the effective elastic thickness looses its merit for assessing the lithosphere thickness. We show, how strong effective elastic thickness and lithosphere thickness may differ, in which way the viscoelastic structure of the Earth influences this difference for glacial loads and which consequences arise for the lithospheric stress state.