CC - CATEGORY CODES: 12-Stratigraphy; 16-Structural-geology
DT - DOCUMENT TYPE: Serial; Conference-Document
BL - BIB LEVEL: Analytic
MC - MAP COORDINATES: LAT: S040000; N110000; LONG: W0660000; W0790000.
IL - ILLUSTRATION: Refs: 30; strat. col., sketch maps.
RF - REFERENCE SOURCE: GeoRef, Copyright 2000, American Geological Institute.
IS - ISSN: 0379-6825
IB - ISBN: 0-8093-1170-4
CO - CODEN: CSGCAG
AN - ACCESSION NUMBER: 1984-056224
UD - UPDATE CODE: 1984
Registro 1004 de 5614 - GeoRef Disc 2: 1975-1984
TI - TITLE: Azimuth, energy, Q, and temperature; variations on P wave amplitudes in the United States.
AU - AUTHORS: Butler-Rhett
AF - AUTHOR AFFILIATION: Univ. Colo./NOAA, Coop. Inst. Res. Environ. Sci., Boulder, CO, United States
SO - SOURCE: Reviews of Geophysics and Space Physics. 22; 1, Pages 1-36. 1984.
PB - PUBLISHER: American Geophysical Union. Washington, DC, United States. 1984.
CP - COUNTRY OF PUBLICATION: United-States
PY - PUBLICATION YEAR: 1984
LA - LANGUAGE: English
AB - ABSTRACT: Mean relative P wave (1 s) amplitude characteristics are determined for standardized seismic stations in the United States. Data are compiled from three azimuths: to the north, explosions in Russia; to the northwest, earthquakes along the Asian-Pacific arc; and to the south-southeast, earthquakes in South America. Characteristic receiver amplitudes are found to be azimuthally dependent. High-amplitude areas occur in the central United States, and lowest amplitudes occur along the Rocky Mountain front range and the Rio Grande rift zone. Amplification effects of low-velocity sediments are significant in the central United States. Azimuthal amplitude variations in the eastern United States are consistent with an anomalous attenuating or defocusing body in the lower mantle beneath Colombia, South America. Nonazimuthal amplitude studies are tied to the azimuthal data set to increase station amplitude coverage. Assuming that the variations of anelastic attenuation occur in the upper 400 km of the Earth, high-amplitude stations may be unattenuated, low-amplitude stations are consistent with Q approximately 110, and a mean amplitude implies Q approximately 220-240. The range of variation of Q is mapped into temperature variations, assuming a thermally activated Q mechanism and an olivine activation energy for the upper mantle. The apparent Q variations are consistent with temperature variations of 135 degrees -287 degrees C between high- and low-amplitude seismic station sites.--Modified journal abstract.
AB - ABSTRACT: A hitherto unknown lithological unit was discovered in the course of regional geological mapping carried out by INGEOMINAS, in the W of the Tolima Department (Colombia). This new unit, for which the authors propose the name "Amoya Formation", crops out in the valleys of the Amoya and Ambeima rivers, and in the Quebrada Grande, to the W of Chaparral. It consists of a monotonous black pelite sequence with sporadic intercalations of fine-grained quartzose sandstones which appear to have suffered intense diagenesis or incipient regional metamorphism (angiometamorphism). The unit is cut by dikes and porphyritic bodies, which represent the roots of the overlying Saldana Formation volcanites. The thickness of the outcropping series reaches several hundred meters.
AB - ABSTRACT: The Magdalena Fan can be divided into: upper fan-1:60-1:110 gradients, channels with well-developed levees, generally several subbottom reflectors on 3.5-kHz records, and fine-grained sediments; middle fan-1:110-1:200 gradients, channels with very subdued levees, several to few sub-bottom reflectors on 3.5-kHz records, and chaotic and discontinuous reflections on multichannel seismic (MCS) records; lower fan-<1:250 gradients, small channels and relatively smooth seafloor, generally coarse-grained sediments, few to no subbottom reflectors on 3.5-kHz records, and flat continuous reflections on MCS records. In addition to the turbidity currents, slumping along the continental slope and elsewhere also influence sedimentation in the fan.