GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Online Resource
    Online Resource
    Local earthquake tomography of Central America : structural variations and fluid transport in the Nicaragua-Costa Rica subduction zone (2010)
    Details Availability
    Keywords: Hochschulschrift ; Nicaragua ; Costa Rica ; Kontinentalrand ; Subduktion ; Erdbeben
    Type of Medium: Online Resource
    Pages: Online-Ressource
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-28988
    URL: http://d-nb.info/1019951737/34
    URL: http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_00002898
    URN: urn:nbn:de:gbv:8-diss-28988
    DDC: 551.13601551220287
    Language: English
    Note: Kiel, Univ., Diss., 2008
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GEOMAR CATALOGUE
    Link to Library Catalog
    get availability status
  • 12
    Online Resource
    Online Resource
    Acquisition and inversion of dispersive seismic waves in shallow marine environments (2003)
    Details Availability
    Keywords: Hochschulschrift ; Schelfmeer ; Seismische Welle ; Wellenausbreitung
    Description / Table of Contents: Dispersive Scholte waves as well as acoustic guided waves have been excited by surface towed airguns and recorded with stationary receivers (OBS) and a towed hydrophone array. The inversion of the recorded wavefield spectra was adapted to the data from shallow marine environments. The dispersive interface wave travelling along the sea floor (Scholte Wave) is sensitive to the shear wave velocity (Vs) of the sediment and could be sucessfully recorded and inverted at different sites in Kiel Bay and the south-east rim of the Arkona Basin in the Baltic Sea. Limitations remain for very soft sediments with Vs 〈 50m/s. The acoustic guided wave is sensitive to density and compressional velocity (Vp) as well as Vs. Shear wave velocity and high resolution Vp information could be obtained from the inversion of this wave type in the central Arkona Basin, where very soft sediments (10-20m) overlaid the till and chalk layers, and no interface wave was observed...
    Type of Medium: Online Resource
    Pages: Online-Ressource (211 S. = 36.33 MB, Text) , Ill., graph. Darst., Kt.
    Edition: [Electronic ed.]
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-7823
    URL: http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_782
    URN: urn:nbn:de:gbv:8-diss-7823
    Language: English
    Note: Kiel, Univ., Diss., 2003
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GEOMAR CATALOGUE
    Link to Library Catalog
    get availability status
  • 13
    facet.materialart.
    Unknown
    On‐site non‐destructive determination of the remanent magnetization of archaeological finds using field magnetometers (2021)
    Details
    Publication Date: 2022-09-22
    Description: The determination of the natural remanent magnetization (NRM) of archaeological features can be used for magnetic modelling, joining of shards, archaeomagnetic dating or the investigation of the firing–cooling–collapsing order of ancient buildings. The measurement of NRM is normally conducted on cylindrical or cubic samples in the laboratory. Nevertheless, archaeological finds should preferably not be destroyed, and laboratory instruments are high in costs. Therefore, we propose a lightweight and portable measurement set‐up including already available field magnetometers (preferably caesium magnetometers) in which the archaeological sample of arbitrary shape, in our case a piece of daub, is mounted inside a gimbal to be rotated in all directions. The magnetic field of the sample is measured at a large number of rotational positions with the magnetometer kept at fixed position. In these measurements, the unknown direction of the NRM vector of the sample is rotated, whereas the average magnetic susceptibility of the sample and the ambient magnetic field are constant and known. Hence, the vector of NRM can be determined through least‐squares inversion. For the inversion computation, the sample volume is discretized either as voxel model or approximated as an equivalent sphere. Under certain conditions depending on sample–sensor distance, dipole moment and radius of the sample, the approximation by a sphere is valid without effect on the accuracy of results. Empirically determined functions quantifying these conditions for different sensor sensitivities and noise levels are provided. Validation with laboratory measurements on palaeomagnetic subsamples from the destroyed daub samples indicate that the NRM can be determined by our proposed method with a maximum error in inclination of 2°, in declination of 20° and in magnetization of ±0.6 A/m. This is accurate enough, for example, to determine from daub pieces of burnt house remains whether the building was burnt and cooled before or after it collapsed.
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:622.15
    Language: English
    Type: doc-type:article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 14
    facet.materialart.
    Unknown
    A novel seismic full waveform inversion approach for assessing the internal structure of a medieval sea dike (2023)
    Details
    Publication Date: 2024-05-22
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Coastal protection in the form of dike constructions has a long history at the German North Frisian coast dating back to the High Middle Ages. As the vast majority of the dikes built prior to the devastating storm surges of the Middle Ages have been irretrievably destroyed, mostly sparse remains and only a few well preserved of these medieval dikes are found along the German North Frisian coast and within the Wadden Sea. Not all details of their construction and dimensions are yet understood. In the present case study, we investigate the historical Schardeich on the island of Pellworm in the German North Sea in a noninvasive way using shear waves (SH‐waves). For the data interpretation, we applied a combination of seismic full waveform inversion and classical seismic reflection imaging to determine the interior structure of the dike and its underlying layers at the highest possible resolution. The results obtained on land are compared with dike remains found in the tidal flats. These remains show up in marine seismic sections as characteristic reflections, which probably represent a compaction layer caused by the load of the former dike. For ground truthing, we compare the seismic results with internal dike structures found in nearby excavations. The comparison highlights that FWI is a reliable tool for near‐surface archaeological prospecting. We find that SH‐wave FWI provides decimetre‐scale velocity and density models that allow, together with the seismic reflection section, to determine distinct construction phases of the dike. The investigated dike further shows a depression at base level of about 0.75 m, which is of the same order as observed for the dike base reflections in the tidal flats. Transferring these findings to the dike remains mapped in the tidal flats, we derive a height of the former dike from 2.2 to 4.4 m.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:622.1592 ; archaeogeophysics ; high‐resolution seismic reflection imaging ; seismic full waveform inversion ; shear‐wave seismic
    Language: English
    Type: doc-type:article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 15
    facet.materialart.
    Unknown
    Low-Frequency Seismicity at Villarrica Volcano: Source Location and Seismic Velocities (2021)
    Details
    Publication Date: 2021-10-01
    Description: Villarrica Volcano (Chile) is one of the most active volcanoes in South America. Its low-frequency (≤5 Hz) seismicity consists of a continuous tremor, overlain by impulsive transient events of higher amplitude in 60-s intervals. This signal was recorded in March 2012 by an extensive local network, comprising 75 stations and including 6 subarrays. It allowed us to apply and compare three techniques to locate the origin of the seismicity: intersection of propagation directions determined by array analysis, mapping amplitudes, and modeling of amplitude decay. All methods yield almost identical, temporally stable, epicenters inside the summit crater, which confirms earlier attributions of the seismicity to volcanic activity inside the conduit. The discrete transients and the interevent tremor share the same source location. From the dominance of surface waves and the obvious scattering, we infer a source near the surface. For two arrays at the northern and western flank, a dispersion relation was derived, which allowed for the determination of S wave velocity-depth functions. At both locations, the velocity structure can be modeled by three layers with interfaces at 100 and 400m depths. The velocities (300 to 3,000 m/s) correspond to pyroclastic material at different states of consolidation. The modeling of the amplitude decay reveals a quality factor around 50.
    Keywords: 551.22 ; volcano seismology ; beamforming ; amplitude decay ; source location ; scattering ; S wave velocity structure
    Language: English
    Type: map
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 16
    facet.materialart.
    Unknown
    Automated facies identification by Direct Push‐based sensing methods (CPT, HPT) and multivariate linear discriminant analysis to decipher geomorphological changes and storm surge impact on a medieval coastal landscape (2021)
    Details
    Publication Date: 2022-03-23
    Description: In ad 1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north‐western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long‐term as well as event‐related short‐term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)‐based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtain in situ high‐resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge‐related land losses.
    Description: Presenting a new approach of automated facies identification based on palaeoenvironmental parameter (PEP) analyses of vibracores, Direct Push‐based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) sensing data, linear discriminant analysis (LDA) and seismic measurements, gradual as well as extreme landscape changes associated with major storm surges in ad 1362 and ad 1634 are reconstructed for a study area in the Wadden Sea of North Frisia (Germany). image
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Research Foundation http://dx.doi.org/10.13039/100005930
    Keywords: ddc:551.36 ; ddc:550.724
    Language: English
    Type: doc-type:article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 17
    facet.materialart.
    Unknown
    Prehistoric chamber tombs or geological pitfall? A multimethod case study from Ancient Aigeira with a focus on seismic full‐waveform inversion (2021)
    Details
    Publication Date: 2022-06-17
    Description: We show an extensive multimethod geophysical study of focusing on some enigmatic subsurface structures found at Ancient Aigeira (N Peloponnes, Greece) that could be interpreted either as prehistoric chamber tombs or complex weathering patterns of the local marl–conglomerate rock sequences. It turns out that the nonseismic methods do not allow to distinguish between an archaeological and a geological origin of the observed patterns with certainty. In contrast, we demonstrate how shear‐wave seismics and full‐waveform inversion (FWI) can be used in archaeological prospection for distinguishing between these alternative essentially different interpretational models that are not distinguishable through nonseismic prospection data. The example site Aigeira is strategically well located on a hill on the Northern Peloponnese overlooking the Corinthian Gulf and has been inhabited with occupational gaps since Middle Neolithic times until the 12th to early 14th century ce. Magnetics, ground‐penetrating radar (GPR) and electrical resistivity tomography (ERT) reveal a honeycomb‐shaped anomaly pattern that could have been interpreted as a system of prehistoric chamber tombs. The time‐domain SH‐FWI strategy based on a sequential inversion of low‐pass and band‐pass filtered data results in subsurface models for shear‐wave velocity and density that accurately fits the complicated seismic data set. A highly heterogeneous subsurface is revealed that is characterized by linear cracks on a decimetre scale. The seismic FWI results are compared in detail with GPR, ERT and among each other. It turns out that the FWI result is consistent with each of these other geophysical methods but provides a more comprehensive subsurface characterization that it is supported by corings in addition. With the help of the seismic survey, we can reject the interpretation hypothesis of a prehistoric cemetery with chamber tombs and confirm that the enigmatic geophysical patterns represent a geological weathering structure that could be addressed as a reincised fan delta draped by reddish palaeosols.
    Description: Land Schleswig‐Holstein http://dx.doi.org/10.13039/100018877
    Description: Institute of Aegean Prehistory (INSTAP) http://dx.doi.org/10.13039/100001182
    Description: Ephorate of Antiquities of Achaia
    Description: Hellenic Ministry of Culture and Sport
    Description: Austrian Archaeological Institute and the Austrian Academy of Sciences
    Keywords: ddc:622.1592 ; ddc:930.1
    Language: English
    Type: doc-type:article
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...