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  • 1985-1989  (2)
  • 1975-1979  (3)
Document type
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    New pop-up type Ocean Bottom Seismometer (1986)
    Springer
    Marine geophysical researches 8 (1986), S. 187-199 
    Details
    ISSN: 1573-0581
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We designed a new pop-up type Ocean Bottom Seismometer (OBS) in order to study micro-earthquakes in off-shore areas. With a 57 cm O.D. sphere of high tension aluminium alloy, the OBS system, including one vertical and one horizontal geophone, can safely operate on ocean floors of up to 6000 m depth for seismic observations. The amplified seismic data and the time code are directly recorded on the four-channel cassette deck for periods of up to one month. The frequency response curve throughout the recording and play-back system is flat for the range, 1–15 Hz (−3 dB). The anchor release and the geophone clamp are operated by an acoustic command signal. So far, we have deployed our OBS's 42 times in the ocean. All of the OBS's deployed have been recovered safely. Seismic data has provided seismological evidence for a number of processes associated with tectonism along subduction zones and spreading ridges (e.g., Eguchi et al., 1986).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338228
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Some properties of surf-beats (1979)
    Springer
    Journal of oceanography 35 (1979), S. 9-25 
    Details
    ISSN: 1573-868X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Long ocean waves with periods of several minutes (surf-beats) were observed at a marine observation tower. We have analysed time series data of an envelope of incident swell, long period current velocity and surface elevation fluctuations. Current velocity was measued by an electromagnetic flow meter. Surf-beats amplitudeH (l) is shown to be proportional to 3/2 power of incident swell amplitudeH (s), and decreases with increase of depthh in proportional toh −1/2 such thatH (l) ∼H (s) (H (s)/h)1/2. Frequency energy density functionP LL (f) of surface elevation had two dominant peaks whose frequencies were highly stable through the entire observational period. Cross-spectral analysis suggested that those peaks correspond to traveling edge waves caused by the excess momentum and mass flux in the surf zone. The forced long ocean waves predicted byLonguet-Higgins andStewart (1964) was ditected. Phase-shift and wave height of the wave with respect to those of incident swell envelope are shown to be in remarkable agreement with the predictions. However the forced long wave is only a minor component in the total energy of surf-beats. Current fields are shown to be largely composed of non-surface modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02108278
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of directional spectrum of wind waves using an array of wave detectors Part II. Field observation (1975)
    Springer
    Journal of oceanography 31 (1975), S. 25-42 
    Details
    ISSN: 1573-868X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The directional spectrum of wind waves was observed using seven wave gauges at the marine observation tower. Directional spectrum was calculated by the method described inFujinawa (1974 a) which assures the high directional resolving power. Under the nearly uniform condition of the wind the process of wave development was studied by the use of the data of the directional spectrum. The analysis revealed that, 1) the mean wave direction does not necessarily coincide with the wind direction, 2) the directional spreading is much narrower than hitherto reported, 3) the growth rate is closely proportional to the square of cosine of the angle between the wave direction and the wind direction, 4) the resonancetype wave-wave interaction plays only minor role in the process of wave development for any wave component in the earlier stage of development and for the most rapidly developing component in the main stage of development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02108216
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Reply (1975)
    Springer
    Journal of oceanography 31 (1975), S. 176-177 
    Details
    ISSN: 1573-868X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02107109
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    A widespread simultaneous increase of the microearthquake seismicity and minor crustal movements in and around the assumed rupture zone of the Tokai earthquake (1988)
    Springer
    Natural hazards 1 (1988), S. 255-276 
    Details
    ISSN: 1573-0840
    Keywords: Earthquake prediction ; precursor ; seismicity ; ground tilt ; strain ; pre-slip ; model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Data from an extensive routine network and a high-density temporary seismic observation using the ocean bottom seismometer in and around Suruga Bay, Japan, showed that a simultaneous increase of microearthquake seismicity occurred from mid-July 1984 (Ukawa et al., 1988). The area extended over a region of about 60 km (NS) × 80 km (EW), and is nearly included in the assumed fault zone of the presumed Tokai earthquake. The analyses of the bore-hole ground tilt and volumetric strain data revealed that an anomalous small ground tilt and volumetric strain change occurred at the time of the seismic activity with a duration of about a month. Data of geodetic measurements, groundwater, and radon content were examined with the result that many observational items showed small anomalies during that period. The observed crustal movement was compared with that of slip models of the Philippine Sea plate around Suruga Bay, suggesting that some type of episodic aseismic subducting motion occurred and, thus, caused a crustal movement in the overlying continental plate in the very region of the future fault zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00137231
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    Paper (German National Licenses)
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