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  • 1
    Electronic Resource
    Electronic Resource
    Internally and externally guided voluntary saccades in unmedicated and medicated schizophrenic patients. Part II. Saccadic latency, gain, and fixation suppression errors (1999)
    Springer
    European archives of psychiatry and clinical neuroscience 249 (1999), S. 7-14 
    Details
    ISSN: 1433-8491
    Keywords: Key words Saccades ; Latency ; Gain ; Fixation ; suppression error ; Neuroleptics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Saccades were elicited in 30 schizophrenic patients before medication, in 17 of them during medication with neuroleptics, and in 12 healthy controls using six paradigms that tested different types of saccades: (a) the externally triggered and visually guided saccades; (b) the externally triggered and internally guided saccades (anti-saccades); and (c) the internally triggered and internally guided saccades (memory-guided saccades). Latency of the primary saccade, gain (eye amplitude to target amplitude), and percentage of unwanted saccades (fixation suppression errors) were calculated. The externally triggered and externally guided saccades were only slightly affected in the patients, indicating that the function of parieto-tectal pathways was preserved. In contrast, the internally guided and externally triggered saccades showed abnormally long latencies, slightly smaller gains, and an increased rate of suppression errors regardless of the medication status. These findings were even more pronounced in the internally triggered and internally guided saccades such as memory-guided saccades. According to animal experiments and studies on patients with disorders of the basal ganglia, the performance of these saccades is based on the function of the pre- and dorsolateral frontal cortex and its connections to the basal ganglia. The minimal improvement of some of the parameters after clinical improvement and during treatment with neuroleptics suggests that the eye-movement deficits are associated with abnormalities of schizophrenia, which do not basically change under medication with neuroleptics. The observed effects of neuroleptics also argue against a primary abnormality in the dopaminergic input to the frontal cortex – basal ganglia oculomotor loop and support the view that there is a primary disturbance of the cortical input to the oculomotor loop through the basal ganglia in schizophrenics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004060050059
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The evolution of a global magma ocean with olivine flotation (1991)
    Springer
    Earth, moon and planets 54 (1991), S. 59-65 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We investigate the thermal evolution of a global magma ocean divided by a dunite septum into a shallow and a lower part with help of simple stability estimations and cooling time calculations. It comes out that the septum is not stable against thermal convection so that this mechanism for a separated chemical evolution of the two mantle regions does not work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00055047
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    Paper (German National Licenses)
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  • 3
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    Defining megathrust tsunami source scenarios for northernmost Cascadia (2018)
    Springer
    In:  Natural Hazards, 94 (1). pp. 445-469.
    Details
    Publication Date: 2021-02-08
    Description: For assessing tsunami hazard in northernmost Cascadia, there is an urgent need to define tsunami sources due to megathrust rupture. Even though the knowledge of Cascadia fault structure and rupture behaviour is limited at present, geologically and mechanically plausible scenarios can still be designed. In this work, we use three-dimensional dislocation modelling to construct three types of rupture scenarios and illustrate their effects on tsunami generation and propagation. The first type, buried rupture, is a classical model based on the assumption of coseismic strengthening of the shallowest part of the fault. In the second type, splay-faulting rupture, fault slip is diverted to a main splay fault, enhancing seafloor uplift. Although the presence or absence of such a main splay fault is not yet confirmed by structural observations, this scenario cannot be excluded from hazard assessment. In the third type, trench-breaching rupture, slip extends to the deformation front and breaks the seafloor by activating a frontal thrust. The model frontal thrust, based on information extracted from multichannel seismic data, is hypothetically continuous along strike. Our low-resolution tsunami simulation indicates that, compared to the buried rupture, coastal wave surface elevation generated by the splay-faulting rupture is generally 50–100% higher, but that by trench-breaching rupture is slightly lower, especially if slip of the frontal thrust is large (e.g. 100% of peak slip). Wave elevation in the trench-breaching scenario depends on a trade-off between enhanced short-wavelength seafloor uplift over the frontal thrust and reduced uplift over a broader area farther landward.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s11069-018-3397-6
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Gas hydrate on the northern Cascadia margin: regional geophysics and structural framework (2006)
    Texas A & M University
    In:  Proceedings of the Integrated Ocean Drilling Program, 311 .
    Details
    Publication Date: 2020-06-08
    Description: Integrated Ocean Drilling Program Expedition 311 is based on extensive site survey data and historic research at the northern Cascadia margin since 1985. This research includes various regional geophysical surveys using a broad spectrum of seismic techniques, coring and logging by the Ocean Drilling Program Leg 146, heat flow measurements, shallow piston coring, and bottom video observations across a cold-vent field, as well as novel controlled-source electromagnetic and seafloor compliance surveying techniques. The wealth of data available allowed construction of structural cross-sections of the margin, development of models for the formation of gas hydrate in an accretionary prism, and estimation of gas hydrate and free gas concentrations. Expedition 311 established for the first time a transect of drill sites across the northern Cascadia margin to study the evolution of gas hydrate formation over the entire gas hydrate stability field of the accretionary complex. This paper reviews the tectonic framework at the northern Cascadia margin and summarizes the scientific studies that led to the drilling objectives of Expedition 311 Cascadia gas hydrate.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.2204/iodp.proc.311.109.2006
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Data report: A downhole electrical resistivity study of northern Cascadia marine gas hydrate (2008)
    Texas A & M University
    In:  Proceedings of the Integrated Ocean Drilling Program, 311 .
    Details
    Publication Date: 2020-06-08
    Description: Downhole electrical resistivity measurements can be exploited for gas hydrate concentration estimates. However, to do so requires that several assumptions be made, in particular about in situ pore water salinity and porosity. During Integrated Ocean Drilling Program Expedition 311, electrical resistivity was measured in four boreholes along a transect across the northern Cascadia margin, offshore Vancouver Island, Canada. Logging-while-rilling and conventional wireline logging data of resistivity, density, and neutron-porosity are used together with measurements of porosity and pore water salinity of the recovered core to systematically estimate gas hydrate concentrations at these four sites. Using Ar- chie’s law, empirical parameters a and m are determined from gas hydrate–free zones by means of a Pickett plot. The in situ salinity baseline trend for each site was estimated directly from the measured pore water salinity values, as well as indirectly by calculating the trend using Archie’s law and simultaneously solving for gas hydrate saturation and in situ salinity. Results showed that the in situ salinities at Sites U1325, U1326, and U1329 were well determined from a smooth trend through the highest measured salinity values of the recovered core. Only Site U1327 exhibitsstrongly decreasing pore water salinity, reaching 22‰ at the base of the gas hydrate stability field. This regional low salinity requires special analyses to estimate gas hydrate concentration from resistivity and introduces a large uncertainty. It is suggested that the decreased salinity results largely (90%) from a deeper fresh water source with the remaining freshening being the result of dissociation of pervasive gas hydrate (~3% of the pore space). Considering estimates from density porosity to be the most accurate, gas hydrate saturations average ~9% ± 7% at Site U1326, ~10% ± 7% at Site U1325, and 11% ± 7% at Site U1327 over the entire range of gas hydrate occurrence. No significant gas hydrate is inferred at Site U1329, although small am ounts may be present just above the bottom-simulating reflector. In two localized zones at Site U1326 (60–100 mbsf [meters below seafloor]) and Site U1327 (120–150 mbsf), significantly higher gas hydrate concentrations of 〉30% of the pore space were encountered.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.2204/iodp.proc.311.203.2008
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Submarine landslides offshore Vancouver Island along the northern Cascadia margin, British Columbia: why preconditioning is likely required to trigger slope failure (2016)
    Springer
    In:  Geo-Marine Letters, 36 (5). pp. 323-337.
    Details
    Publication Date: 2019-02-01
    Description: Bathymetric data reveal abundant submarine landslides along the deformation front of the northern Cascadia margin that might have significant tsunami potential. Radiocarbon age dating showed that slope failures are early to mid-Holocene. The aim of this study is the analysis of slope stability to investigate possible trigger mechanisms using the factor of safety analysis technique on two prominent frontal ridges. First-order values for the earthquake shaking required to generate instability are derived. These are compared to estimated ground accelerations for large (M=5 to 8) crustal earthquakes to giant (M=8 to 9) megathrust events. The results suggest that estimated earthquake accelerations are insufficient to destabilize the slopes, unless the normal sediment frictional resistance is significantly reduced by, for example, excess pore pressure. Elevated pore pressure (overpressure ratio of 0.4) should significantly lower the threshold for earthquake shaking, so that a medium-sized M=5 earthquake at 10 km distance may trigger submarine landslides. Preconditioning of the slopes must be limited primarily to the mid- to early Holocene as slope failures are constrained to this period. The most likely causes for excess pore pressures include rapid sedimentation at the time of glacial retreat, sediment tectonic deformation, and gas hydrate dissociation as result of ocean warming and sea level rise. No slope failures comparable in size and volume have occurred since that time. Megathrust earthquakes have occurred frequently since the most recent failures in the mid-Holocene, which emphasizes the importance of preconditioning for submarine slope stability.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1007/s00367-016-0452-8
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  • 7
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    Characterizing the thermal regime of cold vents at the northern Cascadia margin from bottom-simulating reflector distributions, heat-probe measurements and borehole temperature data (2010)
    Springer
    In:  Marine Geophysical Researches, 31 (1-2). pp. 1-16.
    Details
    Publication Date: 2015-11-18
    Description: Several cold vents are observed at the northern Cascadia margin offshore Vancouver Island in a 10 km2 region around Integrated Ocean Drilling Program Expedition 311 Site U1328. All vents are linked to fault systems that provide pathways for upward migrating fluids and at three vents methane plumes were detected acoustically in the water column. Downhole temperature measurements at Site U1328 revealed a geothermal gradient of 0.056 ± 0.004°C/m. With the measured in situ pore-water salinities the base of methane hydrate stability is predicted at 218–245 meters below seafloor. Heat-probe measurements conducted across Site U1328 and other nearby vents showed an average thermal gradient of 0.054 ± 0.004°C/m. Assuming that the bottom-simulating reflector (BSR) marks the base of the gas hydrate stability zone variations in BSR depths were used to investigate the linkages between the base of the gas hydrate stability zone and fluid migration. Variations in BSR depth can be attributed to lithology-related velocity changes or variations of in situ pore-fluid compositions. Prominent BSR depressions and reduced heat flow are seen below topographic highs, but only a portion of the heat flow reduction can be due to topography-linked cooling. More than half of the reduction may be due to thrust faulting or to pore-water freshening. Distinct changes in BSR depth below seafloor are observed at all cold vents studied and some portion of the observed decrease in the BSR depth was attributed to fault-related upwelling of warmer fluids. The observed decrease in BSR depth below seafloor underneath the vents ranges between 7 and 24 m (equivalent to temperature shifts of 0.07–0.15°C).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s11001-010-9080-2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    A seismic survey to detect natural gas hydrate in the East Sea of Korea (2005)
    Springer
    In:  Marine Geophysical Researches, 26 (1). pp. 51-59.
    Details
    Publication Date: 2015-11-25
    Description: Recently, several countries have conducted projects to explore and develop natural gas hydrate, which is one of the new alternative energy resources for the future. In Korea, a five-year national research project was initiated in 2000. As part of this project, a seismic survey was performed in the East Sea of Korea to quantify the potential magnitude and distribution of natural gas hydrates. Multi-channel seismic data and core samples have been acquired and recovered in the survey area. Analysis of seismic data show clear bottom simulating reflectors (BSRs), seismic blank zones (or wipe-out zones) with velocity pull-up structure, and pock-marks. In this study, we present the results of seismic surveys which indicate the existence of natural gas hydrates in Korean offshore areas. These results will be applied to select areas for coring (or drilling) and detailed exploration such as 2D seismic survey with long offset or 3D seismic in the future.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s11001-005-6975-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Geothermal modeling of the gas hydrate stability zone along the Krishna Godavari Basin (2010)
    Springer
    In:  Marine Geophysical Researches, 31 (1-2). pp. 17-28.
    Details
    Publication Date: 2015-11-18
    Description: A wide-spread bottom simulating reflector (BSR), interpreted to mark the thermally controlled base of the gas hydrate stability zone, is observed over a close grid of multichannel seismic profiles in the Krishna Godavari Basin of the eastern continental margin of India. The seismic data reveal that gas hydrate occurs in the Krishna Godavari Basin at places where water depths exceed 850 m. The thickness of the gas hydrate stability zone inferred from the BSR ranges up to 250 m. A conductive model was used to determine geothermal gradients and heat flow. Ground truth for the assessment and constraints on the model were provided by downhole measurements obtained during the National Gas Hydrate Program Expedition 01 of India at various sites in the Krishna Godavari Basin. Measured downhole temperature gradients and seafloor-temperatures, sediment thermal conductivities, and seismic velocity are utilized to generate regression functions for these parameters as function of overall water depth. In the first approach the base of gas hydrate stability is predicted from seafloor bathymetry using these regression functions and heat flow and geothermal gradient are calculated. In a second approach the observed BSR depth from the seismic profiles (measured in two-way travel time) is converted into heat flow and geothermal gradient using the same ground-truth data. The geothermal gradient estimated from the BSR varies from 27 to 67°C/km. Corresponding heat flow values range from 24 to 60 mW/m2. The geothermal modeling shows a close match of the predicted base of the gas hydrate stability zone with the observed BSR depths.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s11001-010-9089-6
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    4D seismic time-lapse monitoring of an active cold vent, northern Cascadia margin (2007)
    Springer
    In:  Marine Geophysical Researches, 28 (4). pp. 355-371.
    Details
    Publication Date: 2015-11-18
    Description: Two single-channel seismic (SCS) data sets collected in 2000 and 2005 were used for a four-dimensional (4D) time-lapse analysis of an active cold vent (Bullseye Vent). The data set acquired in 2000 serves as a reference in the applied processing sequence. The 4D processing sequence utilizes time- and phase-matching, gain adjustments and shaping filters to transform the 2005 data set so that it is most comparable to the conditions under which the 2000 data were acquired. The cold vent is characterized by seismic blanking, which is a result of the presence of gas hydrate in the subsurface either within coarser-grained turbidite sands or in fractures, as well as free gas trapped in these fracture systems. The area of blanking was defined using the seismic attributes instantaneous amplitude and similarity. Several areas were identified where blanking was reduced in 2005 relative to 2000. But most of the centre of Bullseye Vent and the area around it were seen to be characterized by intensified blanking in 2005. Tracing these areas of intensified blanking through the three-dimensional (3D) seismic volume defined several apparent new flow pathways that were not seen in the 2000 data, which are interpreted as newly generated fractures/faults for upward fluid migration. Intensified blanking is interpreted as a result of new formation of gas hydrate in the subsurface along new fracture pathways. Areas with reduced blanking may be zones where formerly plugged fractures that had trapped some free gas may have been opened and free gas was liberated.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s11001-007-9037-2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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