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  • Seismological Society of America (SSA)  (2)
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  • Seismological Society of America (SSA)  (2)
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  • 1
    Online Resource
    Online Resource
    Simultaneous inversion for earthquake location and velocity structure beneath central Costa Rica
    Seismological Society of America (SSA) ; 1996
    In:  Bulletin of the Seismological Society of America Vol. 86, No. 1A ( 1996-02-01), p. 19-31
    Details
    In: Bulletin of the Seismological Society of America, Seismological Society of America (SSA), Vol. 86, No. 1A ( 1996-02-01), p. 19-31
    Abstract: We have imaged the complex crustal and upper mantle structure beneath central Costa Rica using P-wave arrival times from locally recorded earthquakes. Thurber's (1983) iterative inversion method is used to simultaneously estimate velocities along a three-dimensional grid and hypocentral parameters of local earthquakes. Our data consist of over 12,000 arrival times from more than 1300 earthquakes recorded by stations of a permanent seismographic network in Costa Rica. Our resulting velocity model correlates well with mapped geologic units at very shallow depth and with tectonic features at greater depth. We find low velocities (4.0 to 4.8 km/sec) in the shallow crust (above 10 km) near the active volcanoes and associated with a NW-SE trending late Cretaceous to late Tertiary sedimentary basin southeast of Herradura peninsula. High velocities (5.4 to 5.7 km/sec) in the shallow crust correlate with outcrops of late Jurassic to early Tertiary ultramafic ophiolitic units and with basic Tertiary volcanic units. At depths between 20 and 30 km, high velocities (6.8 to 7.2 km/sec) are associated with the subducting Cocos plate under Costa Rica and two prominent low-velocity bodies (6.3 to 6.5 km/sec) are present about 30 km trenchward of the volcanic arc and along the projection of the aseismic Cocos Ridge as it subducts beneath Costa Rica. The thickened oceanic crust of the Cocos Ridge is most likely responsible for its low velocities. The deep low-velocity anomaly located trenchward of the axis of the volcanoes may indicate the presence of a low-density intrusive resulting from an earlier phase of magmatism, possibly the late Miocene episode that produced the Talamanca intrusive complex.
    Type of Medium: Online Resource
    ISSN: 1943-3573 , 0037-1106
    URL: Article
    DOI: 10.1785/BSSA08601A0019
    Language: English
    Publisher: Seismological Society of America (SSA)
    Publication Date: 1996
    detail.hit.zdb_id: 2065447-9
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Constraints on crustal structure and complex Moho topography beneath Piñon Flat, California, from teleseismic receiver functions
    Seismological Society of America (SSA) ; 1996
    In:  Bulletin of the Seismological Society of America Vol. 86, No. 6 ( 1996-12-01), p. 1830-1844
    Details
    In: Bulletin of the Seismological Society of America, Seismological Society of America (SSA), Vol. 86, No. 6 ( 1996-12-01), p. 1830-1844
    Abstract: We use teleseismic P waves recorded at Piñon Flat Observatory (PFO) to constrain the three-dimensional crustal and upper-mantle velocity structure beneath the station. By forward modeling radial receiver function waveforms, we construct a one-dimensional crustal model that includes a significant shear-velocity inversion at 9 km in depth. Arrivals on the tangential components indicate dip of at least the uppermost discontinuity. Complicated Moho topography, deepening to the northwest of PFO, is suggested by azimuthal dependence of travel times and amplitudes of the receiver functions and travel times of crustal P-wave reverberations. Although fine details cannot be resolved, each of those sets of observations plus mislocation vectors provide strong indications of abrupt Moho topography, possibly including step offsets of several kilometers. This is not only consistent with gravity data in implying Airy isostasy with compensation at Moho depth but extends that model to a much finer length scale than had been resolved.
    Type of Medium: Online Resource
    ISSN: 1943-3573 , 0037-1106
    URL: Article
    DOI: 10.1785/BSSA0860061830
    Language: English
    Publisher: Seismological Society of America (SSA)
    Publication Date: 1996
    detail.hit.zdb_id: 2065447-9
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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