ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
Collection
Language
  • 1
    facet.materialart.
    Unknown
    In:  Geophysical Research Letters 26: 783-786
    Publication Date: 1999
    Keywords: Andes, ANCORP 96, seismology, tectonics/crustal structure, geological interpretation
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2015-09-15
    Description: Upwelling hot mantle plumes are thought to disintegrate continental lithosphere and are considered to be drivers of active continental breakup. The formation of the Walvis Ridge during the opening of the South Atlantic is related to a putative plume-induced breakup. We investigated the crustal structure of the Walvis Ridge (southeast Atlantic Ocean) at its intersection with the continental margin and searched for anomalies related to the possible plume head. The overall structure we identify suggests that no broad plume head existed during opening of the South Atlantic and anomalous mantle melting occurred only locally. We therefore question the importance of a plume head as a driver of continental breakup and further speculate that the hotspot was present before the rifting, leaving a track of kimberlites in the African craton.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2015-07-30
    Description: The causes for the formation of large igneous provinces and hotspot trails are still a matter of considerable dispute. Seismic tomography and other studies suggest that hot mantle material rising from the core-mantle boundary (CMB) might play a significant role in the formation of such hotspot trails. An important area to verify this concept is the South Atlantic region, with hotspot trails that spatially coincide with one of the largest low-velocity regions at the CMB, the African large low shear-wave velocity province. The Walvis Ridge started to form during the separation of the South American and African continents at ca. 130 Ma as a consequence of Gondwana breakup. Here, we present the first deep-seismic sounding images of the crustal structure from the landfall area of the Walvis Ridge at the Namibian coast to constrain processes of plume-lithosphere interaction and the formation of continental flood basalts (Paraná and Etendeka continental flood basalts) and associated intrusive rocks. Our study identified a narrow region (〈100 km) of high-seismic-velocity anomalies in the middle and lower crust, which we interpret as a massive mafic intrusion into the northern Namibian continental crust. Seismic crustal reflection imaging shows a flat Moho as well as reflectors connecting the high-velocity body with shallow crustal structures that we speculate to mark potential feeder channels of the Etendeka continental flood basalt. We suggest that the observed massive but localized mafic intrusion into the lower crust results from similar-sized variations in the lithosphere (i.e., lithosphere thickness or preexisting structures).
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2019
    Description: 〈span〉〈div〉SUMMARY〈/div〉We present a Bayesian approach to solve the problem of simultaneous inversion for optimal hypocentre parameters and 1-D velocity models as well as station corrections for a given set of local earthquakes utilizing a hierarchical, transdimensional Markov chain Monte Carlo (McMC) algorithm. The simultaneous inversion is necessary because of the velocity–hypocentre coupling inherent to the problem.Tests with synthetic arrival time data indicate an excellent performance of the approach, at the same time benefiting from all the advantages related to the McMC algorithm. These advantages are that only minimum prior knowledge is used (i.e. regarding starting focal coordinates, initial velocity model, which are set to random initial values), no regularization parameters (e.g. damping) have to be selected, and the parametrization of the velocity model (i.e. model nodes/layers) is automatically set and adjusted according to the quality of the data, that is noise level. By minimizing the amount of pre-inversion assumptions, which are regularly not available at the required precision or often only available after very careful and time-consuming assessment, the inversion results are therefore almost exclusively data-driven. On output, we obtain a suite of well fitting models which can statistically be analysed and provide direct estimates of the posterior uncertainties of the models.Tests with real arrival time data from a temporary local network deployed in South-Central Chile in 2004 and 2005 show a very good agreement with the results obtained with a conventional inversion method.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Publication Date: 2014-12-05
    Description: The West Iberia Lithosphere and Asthenosphere Structure (WILAS) project densely covered Portugal with broadband seismic stations for 2 yrs. Here we provide an overview of the deployment, and we characterize the network ambient noise and its sources. After explaining quality control, which includes the assessment of sensor orientation, we characterize the background noise in the short-period (SP), microseismic, and long-period (LP) bands. We observe daily variations of SP noise associated with anthropogenic activity. Temporary and permanent stations present very similar noise levels at all periods, except at horizontal LPs, where temporary stations record higher noise levels. We find that median noise levels are extremely homogeneous across the network in the microseismic band (3–20 s) but vary widely outside this range. The amplitudes of microseismic noise display a strong seasonal variation. The seasonality is dominated by very-long-period double-frequency microseisms (8 s), probably associated with winter storms. Stacks of ambient noise amplitudes show that some microseismic noise peaks are visible across the whole ground-motion spectrum, from 0.3 to 100 s. Periods of increased microseismic amplitudes generally correlate with ocean conditions offshore of Portugal. Some seismic records display an interesting 12 hr cycle of LP (100-s) noise, which might be related to atmospheric tides. Finally, we use plots of power spectral density versus time to monitor changes in LP instrumental response. The method allows the identification of the exact times at which LP response changes occur, which is required to improve the understanding of this instrumental artifact and to eventually correct data. Online Material: Figures and movie illustrating the variation of seismic noise amplitudes with sensor type, time, and soil type.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Publication Date: 2019
    Description: 〈span〉〈div〉Summary〈/div〉We present a Bayesian approach to solve the problem of simultaneous inversion for optimal hypocenter parameters and 1-D velocity models as well as station corrections for a given set of local earthquakes utilizing a hierarchical, transdimensional McMC algorithm. The simultaneous inversion is necessary because of the velocity-hypocenter coupling inherent to the problem.Tests with synthetic arrival time data indicate an excellent performance of the approach, at the same time benefiting from all the advantages related to the McMC algorithm. These advantages are that only minimum prior knowledge is used (i.e. regarding starting focal coordinates, initial velocity model, which are set to random initial values), no regularization parameters (e.g. damping) have to be selected, and the parameterization of the velocity model (i.e. model nodes/layers) is automatically set and adjusted according to the quality of the data, i.e. noise level. By minimizing the amount of pre-inversion assumptions, which are regularly not available at the required precision or often only available after very careful and time-consuming assessment, the inversion results are therefore almost exclusively data-driven. On output, we obtain a suite of well fitting models which can statistically be analyzed and provide direct estimates of the posterior uncertainties of the models.Tests with real arrival time data from a temporary local network deployed in South-Central Chile in 2004 and 2005 show a very good agreement with the results obtained with a conventional inversion method.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Publication Date: 2013-11-04
    Description: The geothermal potential in Tarutung is controlled by both the Sumatra Fault system and young arc volcanism. In this study we use the spatial distribution of seismic attenuation, calculated from local earthquake recordings, to image the 3-D seismic attenuation of the area and relate it with the temperature anomalies and the fluid distribution of the subsurface. A temporary seismic network of 42 stations was deployed around Tarutung and Sarulla (south of Tarutung) for a period of 10 months starting in 2011 May. Within this period, the network recorded 2586 local events. A high-quality subset of 229 events recorded by at least 10 stations was used for the attenuation inversion (tomography). Path-average attenuation ( $t_{p}^{*}$ ) was calculated by using a spectral inversion method. The spread function, the contour lines of the model resolution matrix and the recovery test results show that our 3-D attenuation model ( Q p ) has good resolution around the Tarutung Basin and along the Sarulla graben. High attenuation (low Q p ) related to the geothermal system is found in the northeast of the Tarutung Basin suggesting fluid pathways from below the Sumatra Fault. The upper part of the studied geothermal system in the Tarutung district seems to be mainly controlled by the fault structure rather than by magmatic activities. In the southwest of the Tarutung Basin, the high attenuation zone is associated with the Martimbang volcano. In the Sarulla region, a low- Q p anomaly is found along the graben within the vicinity of the Hopong caldera.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Publication Date: 1979-03-01
    Print ISSN: 0042-9929
    Electronic ISSN: 1432-1181
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Publication Date: 1977-09-01
    Print ISSN: 0042-9929
    Electronic ISSN: 1432-1181
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...