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  • 1
    Microfilm
    Microfilm
    Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica (2004)
    Associated volumes
    Details Availability
    In: Journal of geophysical research / B, Washington, DC : Union, 1978, 0148-0227
    Description / Table of Contents: New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (~1 year) observation period. We also estimate northwest motion of a coastal "sliver block" at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with ~8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ~1 cm/yr on the Panama blockCaribbean boundary. The GPS data suggest that the Cocos platePanama block boundary is completely locked from ~10-50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.
    Type of Medium: Microfilm
    Pages: graph. Darst
    ISSN: 0148-0227
    DOI: 10.1029/2003JB002931
    Language: English
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  • 2
    Electronic Resource
    Electronic Resource
    Waveform Analysis of Scholte Modes In Ocean Sediment Layers (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 125 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In an effort to determine the characteristics of seismic noise on the ocean bottom and its relationship to the structure of the sea-floor, we have adapted the method of nonlinear waveform fitting to accommodate multidimensional models (shear velocity β and shear damping Qs), and have applied it to invert several records of interface waves (Scholte 1958) from the THUMPER experiment off southern California. Waveform fitting is a very powerful tool to determine the S velocity in the top few metres of the sediment. Starting from β= 30 m s −1 at the top clay layer, the S velocity increases with a gradient of 2.8 m s−1 m−1 over the first 150m of sediment. A theoretical estimation of the source strength gives coherent estimates of Qs as a function of depth for distances between 400 and 1070 m from the source. the Qs models are characterized by very low values (10–20) in the top three metres, but by values in excess of 100 below that level. the results confirm the identification of the noise as harmonics of interface waves. In the area of this experiment, the largest noise amplitudes belong to the fundamental mode and penetrate to a depth of about 20 m into the sediment. the overtone energy can be appreciable too, and is noticeable to about 80 m depth. the Qs structure confirms the strong influence that the sea-floor structure has on the noise spectrum. the high attenuation at frequencies above 3–4 Hz suppresses noise propagation and produces low noise at higher frequencies. (Similarly, high attenuation in the asthenosphere suppresses noise propagation below 0.1 Hz.)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb00006.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A low velocity zone underlying a fast-spreading rise crest (1975)
    [s.l.] : Nature Publishing Group
    Nature 256 (1975), S. 475-476 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Many surveys have been made of the structure in the neighbourhood of slow spreading ridges, particularly the Mid-Atlantic Ridge, but very little work has been done on fast spreading ridges. Two surveys2'3 on the East Pacific Rise near the area of this work show mantle velocities below 8 km s"1. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/256475a0
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A standard format for storage and exchange of natural and explosive-source seismic data: The ROSE format (1983)
    Springer
    Marine geophysical researches 6 (1983), S. 99-105 
    Details
    ISSN: 1573-0581
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The ROSE experiment (Ewing and Meyer, 1982) involved the participation of much of the U.S. marine seismic community. Prior to that experiment, wide consultation was made and much effort was expended in the intercomparison of instruments and in the establishment of a uniform, yet flexible, data exchange format. Results of the instrument intercomparison were reported earlier in this journal (Sutton et al., 1981) and the data exchange format is described in detail here. The participating institutions have provided their data to a central exchange facility at the University of Hawaii where the data are catalogued and distributed. We hope that the use of this format for the exchange of data from other experiments will reduce the time we spend on work of a housekeeping nature, time which is irretrievably lost to the pursuit of our scientific goals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300399
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  • 5
    Electronic Resource
    Electronic Resource
    Instrument calibration of ocean bottom seismographs (1986)
    Springer
    Marine geophysical researches 8 (1986), S. 265-275 
    Details
    ISSN: 1573-0581
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract To increase the accuracy of measuring sea floor motion with ocean bottom seismometers, we calibrate the seismometer system on the ocean floor. Data from the sea floor calibration, augmented with electronic and land calibration data, enables us to find the OBS transfer function to an accuracy of 0.5% in the frequency range of 0.1 to 32 Hz. We are able to distinguish between temperature, instrument and OBS ground coupling effects, all of which alter the transfer function. This paper reviews our method of calibration and discusses the effects of temperature and some of the instrument design features on the vertical seismometer transfer function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305486
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  • 6
    Electronic Resource
    Electronic Resource
    Crustal seismic structure beneath the West Philippine Sea, 17°–18° North (1989)
    Springer
    Marine geophysical researches 11 (1989), S. 155-168 
    Details
    ISSN: 1573-0581
    Keywords: seismic ; refraction ; WKBJ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crustal seismic structures beneath the West Philippine Sea are determined by using explosive sources (0.5–108.6 kg) and ocean bottom seismometers to measure refracted compressional waves. Total crustal thicknesses are shown to be thinner in the eastern part of the ocean basin, approaching only 3.5 km. Crustal thinning toward the east is consistent with the Palau Kyushu Ridge being a remnant transform fault connecting the Central Basin Ridge and the Kula Pacific Ridge in the past. A velocity-depth inversion from the westernmost refraction profile indicates the upper transitional crust layer to have strong velocity gradients which gradually decrease with depth; the lower crust is characterized by a nearly constant velocity gradient. The western part of the ocean basin is also shown to have more typical oceanic thicknesses, as is found in deep ocean basins of the Pacific. Spectral energy models using WKBJ synthetic seismograms suggest that there is a sharp seismic discontinuity between the crust and moho in the western part of the basin. Predicted water depths for the West Philippine Basin using an age-depth relation and corrected for an isostatic response to the measured crustal thicknesses, are still 300 meters shallower than observed depths. The depth anomaly can not be fully reconciled by thinner crust in the eastern part of the basin. This observation implies that a deeper seated anomaly is present beneath the West Philippine Basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340202
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  • 7
    Electronic Resource
    Electronic Resource
    An ocean bottom, microprocessor based seismometer (1981)
    Springer
    Marine geophysical researches 4 (1981), S. 451-477 
    Details
    ISSN: 1573-0581
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We describe the design and construction of an ocean bottom seismometer configured as a computer, based on an Intersil IM6100 microprocessor plus appropriate peripheral devices. The sensors consist of triaxial 1 Hz seismometers and a hydrophone, each sensor channel being filtered prior to digitizing so that typical noise spectra are whitened. Digital data are recorded serially on magnetic tape. The instrument is placed on the ocean bottom by allowing it to fall freely from just below the surface. An acoustic system allows precise determination of instrument position, acoustic recall, and transmission of operational information to the surface. Release from an expendable anchor is accomplished by redundant pyrotechnic bolts which can be fired by acoustic command or by precision timers. The operational flexibility provided by the micro-computer, which executes the DEC PDP8/E DEC, PDP8/E and OS/8 are registered trademarks of Digital Equipment Corporation, Maynard, Mass., USA instruction set, enables optimum use of the 6-hr recording capacity (at 128 samples/second/channel) in the context of the particular experiment being performed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286039
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  • 8
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    Unknown
    Geodetic and seismic constraints on some seismogenic zone processes in Costa Rica (2004)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 109 . B11403.
    Details
    Publication Date: 2018-04-25
    Description: New seismic and geodetic data from Costa Rica provide insight into seismogenic zone processes in Central America, where the Cocos and Caribbean plates converge. Seismic data are from combined land and ocean bottom deployments in the Nicoya peninsula in northern Costa Rica and near the Osa peninsula in southern Costa Rica. In Nicoya, inversion of GPS data suggests two locked patches centered at 14 ± 2 and 39 ± 6 km depth. Interplate microseismicity is concentrated in the more freely slipping intermediate zone, suggesting that small interseismic earthquakes may not accurately outline the updip limit of the seismogenic zone, the rupture zone for future large earthquakes, at least over the short (∼1 year) observation period. We also estimate northwest motion of a coastal “sliver block” at 8 ± 3 mm/yr, probably related to oblique convergence. In the Osa region to the south, convergence is orthogonal to the trench. Cocos-Caribbean relative motion is partitioned here, with ∼8 cm/yr on the Cocos-Panama block boundary (including a component of permanent shortening across the Fila Costeña fold and thrust belt) and ∼1 cm/yr on the Panama block–Caribbean boundary. The GPS data suggest that the Cocos plate–Panama block boundary is completely locked from ∼10–50 km depth. This large locked zone, as well as associated forearc and back-arc deformation, may be related to subduction of the shallow Cocos Ridge and/or younger lithosphere compared to Nicoya, with consequent higher coupling and compressive stress in the direction of plate convergence.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2003JB002931
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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