ALBERT

Beschreibung: The German lake district "Mecklenburger Kleinseenplatte" between Berlin and Rostock shows a great variety of lakes having different trophical states. Remote sensing of water quality is investigated to help monitoring the lake waters and to guide the water sampling more carefully over space and time. Satellite data of the Indian Remote Sensing Satellite of summer 1996 are analysed for a general overview of the variety of lake water within the test area. To get more quantitative information hyperspectral scanner data of the Compact Airborne Spectrographic Imager (casi) are investigated. For these data a ratio of two bands pointing to chlorophyll absorption at 680 nm and a hull function over the absorption band have been applied. The results could be well related to the ground truth data taken by the Institute of Fresh Water Ecology in Brandenburg. They show differences in chlorophyll content even in December, a season of minimal bioproduction. Thus, further research in the summer season is promising to get good results in estimation of water quality parameters.

Beschreibung: Zusammenfasung: In den letzten 20 Jahren ist das globale Netz von Erdbebenstationen (GSN) modernisiert und erweitert worden. Es umfasst jetzt eine grosse Zahl von digitalen Stationen, die die seismischen Signale hochaufloesend ueber einen weiten Frequenzbereich registrieren. Durch diese internationalen Bemuehungen, an denen sich das GFZ im Rahmen des GEOFON-Programms beteiligt, hat sich nicht nur die Qualitaet der Erdbebenueberwachung deutlich verbessert, sondern es ist nun auch moeglich, die Feinstruktur des Erdinnerns mit hoeherer Praezision zu untersuchen. Letzteres wird hier an zwei Beispielen ueber die Tiefenerstreckung von kontinentalen und ozeanischen Strukturen sowie ueber die Feinstruktur der Uebergangszone zwischen oberem und unterem Mantel verdeutlicht. Durch die temporaere Verdichtung seismischer Netze mittels portabler Stationen ist es moeglich, spezifische Fragen zur Struktur der Lithosphaere und das gesamten Erdinnern zu untersuchen. Hierzu werden gewoehnlich Registrierungen von Fernbeben herangezogen, aus denen Strukturbilder in den Tiefen abgeleitet werden koennen, die mit explosionsseismischen Quellen wegen der geringeren abgestrahlten Energie nicht ausreichend durchstrahlt werden koennen. Als Beispiel hierzu zeigen wir Ergebnisse von einem Feldexperiment in Tibet. Abstract Starting about 20 years ago the global network of seismograph stations (GSN) has been upgraded and expanded to a large number of digital stations recording seismic signals with high resolution in a very broad frequency band. This coordinated international effort, with GFZ Potsdam contributing through its GEOFON program, has improved considerably the monitoring capabilities of seismic networks, and it provides the data that allow us to study Earth structure in unpredecedented detail. This is demonstrated for two examples dealing with the depth extent of continental and oceanic structure, and the transition zone between upper and lower mantle. In addition to permanent seismograph stations, portable seismograph networks have been used to temporarily increase the station density in areas of scientific interest, thus enabling detailed studies of both the structure of the lithosphere and the entire globe using data from distant earthquakes. The methods developed for the processing and interpretation of earthquake recorderings have resulted in improved structural images at greater depths that are difficult to probe by explosions because of their limited energy. This is demonstrated in an example of lithospheric and upper mantle studies in Tibet.

Beschreibung: Short-period three-component recordings of the seismic wave field of peaceful nuclear explosions (PNEs) along several long-range profiles in northern Eurasia are analyzed to study the structure of the upper mantle. We use the date to search for evidence of the disputed 520 km discontinuity in the mantle transition zone. Here we present short-period evidence for the existence of this proposed mantle discontinuity. On three long-range profiles in Siberia we observe in the distance range from 2400 to 2600 km a typical change of the apparent velocity of the first arrivals and the appearance of two characteristic travel time branches. We interpret these phenomena as being caused by the proposed upper mantel discontinuity. To determine the optimum one-dimensional P wave velocity model, synthetic seismograms were calculated with the reflectivity method. By comparing them with the observed data, we estimate the P wave velocity contrast across the 520 km discontinuity to be 0.25 +- 0.0005 km/s, while the velocity gradient below the boundary is 0.001 +- 0.0005 1/s. This result indicates that in the mantle transition zone both phase transitions and variations in chemical composition can occur.

Beschreibung: 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.

Beschreibung: 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.

Beschreibung: Hydrogenetic ferromanganese crusts incorporate elements from ambient seawater during their growth on seamounts. By analysing Nd, Pb and Be isotope profiles within crusts it is possible to reconstruct seawater tracer histories. Depth profiles of 10Be/9Be ratios in three Pacific ferromanganese crusts have been used to obtain growth rates which are between 1.4 and 3.8 mm/Ma. Nd and Pb isotopes provide intact records of isotopic variations in Pacific seawater over the last 20 Ma or more. There were only small changes in Pb isotope composition in the last 20 Ma. This indicates a constant Pb composition for the erosional sources and suggests further that erosional Nd inputs may have been uniform too. εNd values vary considerably with time and most probably reflect changes in ocean circulation. The Epsilon(tief:Nd) values of the crusts not only vary as a function of age but also as a function of water depth. From 25 to 0 Ma, crust VAl3/2 from 4.8 km water depth has a similar pattern of εNd variation to the two shallower crusts from 1.8 and 2.3 km, but about 1.0 to 1.5 units more negative. This suggests that εNd stratification in Pacific seawater, as demonstrated for the present day, has been maintained for at least 20 Ma. Each crust shows a decrease in εNd from 3-5 Ma to the present, which is interpreted in terms of an increase in the NADW component present in the Pacific. From 10 to 3-5 Ma ago the crusts show an increase in εNd. This suggests a decreasing role for a deep water source with εNd less than circum-Pacific sources. In this regard the Panamanian gateway restriction from ~ 10 Ma with final closure at 3-5 Ma may have played an important role in reducing access of Atlantic-derived Nd to the Pacific.

Beschreibung: An analysis of the steady-state heat conduction model for the Earth's crust and the upper mantle revealed that the main difficulties in the downward continuation of subsurface geothermal measurements q were connected with an estimation of the heat flow density q"SUB M" at the Moho boundary and of the source distribution f. Solving the steady-state heat conduction equation numerically by means of finite differences (finite elements), we can describe the relation between q, q"SUB M" and f by a linear algebraic system. To overcome the non-uniqueness and instability, a least squares approach is suggested to solve these systems. Bounds for the square-means of the unknown parameters q"SUB M" and f are introduced, whereby it is possible to find solutions with appropriate mean properties. A two-dimensional geothermal profile crossing Central Europe is used to demonstrate this method. The difficulties in estimating reasonable mantle heat flow density and optimal heat source models from geothermal measurements only are pointed out.-Authors

Beschreibung: Ausgehend von der Analyse werrasulfatischer Sedimentgefüge am Osthang der zechsteinzeitlich wirksamen Eichsfeld-Schwelle und ihrem Vergleich mit bekannten Gefügetypen von Beckensulfaten, kann die Entstehung des Sulfatwalles der Eichsfeld-Schwelle und anderer Sulfatwälle des Zechsteinbeckens erklärt und damit ein Beitrag zur paläotektonischen Entwicklung der Mitteleuropäischen Zechsteinsenke geleistet werden. Morphologische Vorbedingungen führen zur Ausbildung unterschiedlicher Lösungstiefen und verursachen dadurch unterschiedlich wirksame Eindunstung. Diese bedingt verstärkten Lösungsnachstrom und damit erhöhte Stoffzufuhr zu den Schwellengebieten. Es entsteht ein starkes Konzentrationsgefälle, das über den Untiefen intensive Sulfatabscheidung, in den Beckenräumen jedoch wegen dort nur allmählich zunehmender Lösungskonzentration die Bildung von geringmächtigen Sulfatlaminiten hervorruft. Bei sich angleichender Lösungskonzentration gelangen Flaseranhydrite, zugleich auf die Schwellenhänge übergreifend, zur Ablagerung. Mehrfach sich wiederholende Lösungeverdünnungen und nachfolgende Konzentrationen erzeugen rhythmisch sich wiederholende Konzentrationsgefälle mit stark unterschiedlichen Sedimentationsraten über Schwellen- und Beckenregionen. Am Schwellenhang bildet sich allmählich eine Sedimentationsterrasse. Längere Perioden anhaltender Lösungsverdünnung bedingen stabile Konzentrations- und Mächtigkeitsungleichgewichte. Sedimentumlagerungen sind die Folge. Die Resedimentation erfaßt zunächst das Lockermaterial der Schwellen. Es entstehen Sulfatturbidite, die auf Grund des Transportmechanismus von Trübeströmen auch über die Schwellenhänge hinaus in benachbarte Beckenräume getragen werden (distale Turbidite) und dort eine Mächtigkeitsaufblähung der Laminite verursachen. Bei extremen Mächtigkeitsungleichgewichten geht die turbiditische Resedimentation in die Umlagerung teilverfestigter und verfestigter Materialien über. Es entstehen Sulfat-Olisthostrome (Osthang der Eichsfeld-Schwelle).

Beschreibung: 1. Einleitung 2. Problemstellung 3. Paläogeographisch-paläotektonischer Rahmen des Untersuchungsgebietes 4. Untersuchungsergebnisse 4.1. Gradierte Werra-Sulfate und ihre Genesebestimmung 4.2. Brekzien des Werra-Sulfats 4.2.1. Genetische Deutung der Sulfatbrekzien 4.2.2. Der Bewegungsmechanismus des Sulfat-Olisthostroms 4.3. Die Beziehungen zwischen sulfatischen Turbidit- und Olisthostrom-Ablagerungen 5. Die Entwicklung der Sedimentationsverhältnisse an der Eichsfeld-Schwelle und ihre Beziehungen zur Beckensedimentation 5.1. Die Herkunft der turbiditischen und olisthostromaren Umlagerungsprodukte 5.2. Der Umlagerungsvorgang und seine Ursachen 5.3. Die Reichweite der turbiditischen und olisthostromaren Umlagerungen 5.4. Die Tiefe des Südharzbeckens 5.5. Die stratigraphische Einordnung der Umlagerungen 5.6. Die Sedimentgefüge der Becken- und Schwellensulfate und ihre Interpretation 5.7. Zu Randerscheinungen der Turbidit- und Olisthostrom-Genese 6. Das Modell der Sedimentationsverhältnisse an der Eichsfeld-Schwelle und im Südharzbecken 7. Paläotektonische Schlußfolgerungen Literatur Anhang (Abbildungen I bis XVII)

Beschreibung: The tables and graphs result from evaluation of Model 1 (see Veröffentlichungen des Zentralinstituts für Physik der Erde, Nr. 41, Potsdam 1976). They help to approximate values of the hydrostatic pressure P, the bulk modulus and its pressure derivative and the seismic parameter of a sample at any volume contraction x in the range between 0.5 and 1 if these quantities referred to the initial state (P = 0) are known. The considered functions are tabulated for a set of grid points of the rectangle 0.5 ≤ x ≤ 1, 2.1 ≤ ϰ_1 ≤ 10, where ϰ_1 is the initial value of the pressure derivative of the bulk modulus. The lattice pitchs are 0.01 in x and 0.1 in ϰ_1. The inverse problem can also be solved approximately with the aid of the tables and, above all, the plots presented here by using the "method of corresponding curves".

Beschreibung: Summary 1. Preface 2. Theoretical excursus 3. Some remarks on Model 1 4. Instructions for using tables and plots 5. References 6. Tables and figures

Beschreibung: The PUNA (Plateau Untersuchung Nw Argentinien) seismograph network was deployed across the Andes at ∼23.5°S. The array was centered in the backarc, atop the Puna high plateau in NW Argentina and was in operation for approximately 100 days between late August and late November 1997. Most stations were equipped with short-period1-Hz 3-component seismometers and PDAS data loggers recording continuously 100 sps. The deployment was part of the collaborative research center „Deformation processes in the Andes - SFB267”. Waveform data are available from the GEOFON data centre, under network code ZB under CC-BY 4.0 license.

Beschreibung: Vorwort EZ, v.v.: Tektonische Deformation und Regionalmetamorphose PATALACHA, E.I.; SMIRNOV, A.V.: Die Hauptmechanismen des plastischen Fließens von Gesteinen bei tektonischen Prozessen und ihre praktische Bedeutung BANKWITZ, P.: Einige Aspekte der Faltenbildung PATALACHA, E.I.; POLJAKOV, A.I.: Regelmäßigkeit und Symmetrie geologischer Strukturen HOFMANN, J.: Quarzge.füge (c-Achsen-Orientierung) der Metamorphite des Erzgebirges und des sächsischen Granulitgebirges als tektonische Indikatoren MATim, G.: Der Einfluß tektonischer Bewegungen auf die metamorphe Kristallisation -- Beispiele aus dem kristallinen Grundgebirge Sachsens KAEMMEL, Th.; MAASS, I.; WAND, u.: Bemerkungen zu Isotopenvariationen des Kohlenstoffs ·in hochinkohlten Substanzen und Graphiten vordevonischer Sedimente und Metamorphite MÖBUS, G.: Einige Gedanken zum Mobilitätsverhalten der Gesteine in der Erdkruste, speziell im Grundgebirge und im glazigen beeinflußten Känozoikum SCHROEDER, E.: Zur zeitlichen Abfolge und zur Korrelation von Deformations- und Metamorphoseetappen PAECH, H.-J.: Versuch einer tektonischen Rayonierung der Faltungszonen Europas unter Berücksichtigung der faltungsbezogenen Deformationsintensitäten (Einengung und Interndeformation)

Beschreibung: The architecture and implementation of a rule-based fuzzy approach to the detection and classification of man made objects in satellite image data are presented. In a first processing step fuzzy clustering is used to obtain an initial coarse presegmentation of the data. Subsequently, a rule-based fuzzy system performs the classification. Its rules are generated both manually (based on common-sense or higher level expert knowledge) and automatically by a neural network evaluating image features which are difficult to extract or to evaluate directly. Some experimental results, a discussion of the potential of the approach and directions of possible future research conclude the paper.

Beschreibung: During the Kenya Rift International Seismic Project (KRISP 90) a 450-km east-west seismic profile was shot across the rift in the vicinity of the Equator. Reflectivity modelling of some of the P- and S-phases combined with results derived from the ray-trace forward model enable more information to be extracted from the data set. The Pg phase at the western end of the profile required a different velocity-depth gradient in the Archaean and the Proterozoic terranes crossed by the profile. This, combined with structural and seismic velocity differences derived from the forward model, provides the means for the two units to be distinguished throughout the whole crust. A phase in the PmP coda from shot points within the rift has been successfully modelled as a PmP multiple reflected from the base of or from within the rift infill. The clearest S-phase on the cross-rift profile, SmS, has been reproduced by reflectivity modelling and compared to the same phase from the KRISP 90 flank line: combining these observations with the results from the spectral analysis of the principal P- and S-phases observed from all the shot points on the cross-rift profile supports the contention that most of the seismic attenuation occurs immediately beneath the rift in the upper crust or in the rift infill, with little attenuation occurring in the lower crust.

Beschreibung: The Middle Urals are characterized by a major virgation in the linear trend of the Urals orogen, and represent the most highly contracted part of the late Palaeozoic collisional belt. This part of the orogen is dominated by metamorphic complexes and major fault and shear zones. The Main Uralian Fault zone (MUF), the east-dipping suture of the orogen containing low-grade metamorphic rocks, separates the Sysert Complex in the east from the Ufaley Complex in the west. The Sysert Complex in the hanging wall of the MUF consists of intensely deformed gneisses, granitic intrusions and a metamorphosed mélange zone. Tectonic and isotopic investigations suggest the following stages for the evolution of the Sysert Complex: (a) pre-orogenic rifting and magmatism during Ordovician and Silurian times; (b) oceanic closure, island arc formation related to convergence and subduction during Devonian times; (c) major ductile deformation under amphibolite facies conditions related to NW-directed thrusting associated with crustal stacking during collision in Carboniferous times; (d) exhumation and contractional intracontinental tectonics during Permian times; and (e) closing of isotope systems related to cooling and the end of orogenic shortening through Triassic times. The Ufaley Complex, in the footwall of the MUF, is interpreted as an east-dipping crustal stack that records an amphibolite facies Uralian metamorphism. Lithologically the complex can be divided into pre-orogenic European basement (West Ufaley) and intensely deformed Palaeozoic metasediments and amphibolites (East Ufaley). High-pressure relics in the East Ufaley Complex are interpreted to be the result of subduction, whereas intense ductile deformation is related to overthrusting onto West Ufaley. The West Ufaley Complex is composed of gneisses, amphibolites, migmatites and granitic intrusions and has been thrust onto Devonian limestones along a major shear zone. In both Sysert and Ufaley Complexes, NW-trending stretching lineations and top-to-the-NW kinematic indicators suggest an oblique plate convergence with a significant sinistral component. The MUF is interpreted as a major normal fault that developed congruent with continental subduction and that compensated lithospheric thickening and the rapid exhumation of subducted crust in the footwall.

Beschreibung: The seismic refraction-wide-angle reflection experiments carried out in 1985 and 1990 in the Kenya rift (KRISP '85 and KRISP '90) show major crustal thickness variations both along and across the rift. Along the rift axis crustal thickness varies from 35 km in the south beneath the Kenya dome to 20 km in the north beneath the Turkana region. Due to the distribution of crustal thickness beneath the rift flanks, it can be stated that the major amount of variation in crustal thickness along the rift axis is due to the Tertiary rifting episode. The northwards decrease in crustal thickness can be correlated with changes in surface topography (northwards decrease), rift width (northwards increase), surface estimates of extension (5–10 km in the south and 35–40 km in the north) and Bouguer gravity, the regional northwards increase of which can be explained entirely by the change in crustal thickness. Below the 750 km long axial rift profile, uppermost mantle P(tief)n velocities are low, being 7.5–7.7 km/s. However, under the northern part of the rift two layers with velocities of 8.1 km/s and 8.3 km/s are embedded in the low-velocity mantle material at 40–45 km and 60–65 km depth, respectively. In contrast, the wide-angle data show that beneath the Kenya dome, in the southern part of the rift, low mantle velocities occur down to at least 65 km depth. This mantle velocity structure is indicative of the depth to the onset of melting being at least 65 km beneath the northern part of the rift and thus not being shallower than the depth (45–50 km) to the onset of melting under the Kenya dome to the south. A profile across the rift north of the Kenya dome at the latitude of Lake Baringo shows that the low uppermost mantle P(tief)n velocity of 7.5–7.7 km/s and crustal thinning of 5–10 km is confined to below the surface expression of the rift. An abrupt change in Moho depths and P(tief)n velocities occurs as the rift boundaries are crossed. Beneath the rift flanks, normal P(tief)n velocities of 8.0–8.2 km/s occur. The presence of hot mantle material beneath the Kenya dome since the onset of volcanism here at 15–20 Ma is still compatible with the abrupt change in mantle P-wave velocities as the rift boundaries are crossed. Petrological interpretation of the seismic velocities indicates a few (up to 5) percent basaltic melt in the mantle below the rift except in the two layers with velocities greater than 8.0 km/s under the northern part of the rift where some crystal orientation (anisotropy) is necessary. Below about 45–50 km depth beneath the southern part of the rift the magma could exist as in situ partial melt. The above results, taken together with results from teleseismic studies, petrology and surface geology, indicate anomalously hot mantle material appearing below the present site of the Kenya rift at about 20–30 Ma. The active uprising of this anomalously hot mantle material since this time has given rise to widespread volcanism along the whole length of the rift and has modified the crust beneath the rift by mafic igneous underplating and intrusion, especially into the basal crustal layer. Accompanying the uprise of the anomalously hot mantle material minor crustal extension (5–10 km) has occurred beneath the Kenya dome in the southern part of the rift where crustal thickness is large (35 km). Under the Turkana region in the northern part of the rift, a greater amount of extension (35–40 km) has taken place and the crustal thickness is small (20 km), although the depth to the onset of melting under the northern part of the rift is, if anything, greater than under the southern part of the rift.

Beschreibung: The architecture of the European Variscides has been subdivided by Kossmat (1927) into paleogeographically coherent units which are presently interpreted as former plate fragments. The Mid-German Crystalline Rise (MGCR) separates two fragments (Rhenohercynian and Saxothuringian belts) at the site of an inferred plate boundary and reequilibrated orogenic root. The commonly favoured model interprets the MGCR as the magmatic arc on Saxothuringian crust above a south-dipping subduction zone in Upper Devonian and Carboniferous times. Data from the MGCR, the kinematic evolution of the Mid-European Variscides, and first order volume balancing suggest a reinterpretation of this unit which challenges classical views on the MGCR as well as on the subdivision of Variscan architecture. The MGCR is composed of two rock groups with different tectonic identity. A Lower Carboniferous low pressure-high temperature magmatic arc association on Lower Paleozoic basement rests tectonically on a stack of medium pressuremedium temperature rocks of inferred Rhenohercynian origin. The latter were tectonically accreted to the base of the overriding plate by tectonic underplating. The entire process was controlled by oblique convergence. This led to regional partitioning of the plate kinematic vector into contractional domains (lower Rhenohercynian plate and back-arc area of the upper Saxothuringian plate), bulk heterogeneous plate margin parallel extensional domains (MGCR), and plate margin parallel wrench domains (MGCR boundaries). During this process material was continually transferred from the lower plate to the upper plate, uplifted and exhumed by net crustal extension. The concomitant removal of parts of the former arc and the entire orogenic root necessitates a reappraisal of Variscan architecture and evolution.