Accession Number : ADA248375


Title :   Lg and Other Regional Phases in South America


Descriptive Note : Scientific rept. no. 2


Corporate Author : OBSERVATORIO SAN CALIXTO LA PAZ (BOLIVIA)


Personal Author(s) : Cabre, Ramon ; Minaya, Estela R ; Ayala, R R ; Capriles, Marcos


Full Text : http://www.dtic.mil/dtic/tr/fulltext/u2/a248375.pdf


Report Date : 23 Oct 1991


Pagination or Media Count : 92


Abstract : Part (1). Seismic phases, especially those following P after a short time, in records of La Paz station (LPB) for South America and neighboring coast earthquakes were revised, trying to identify their nature; a large range of diversity proves the complexity of South American tectonic structures, also in cases apparently identical. Often pP was identified; other arrivals of unclear origin were called provisorily P1, and P2 probably related to Nazca plate subduction; their amplitude, if observable, is much variable. Smallness of P and S phases of earthquakes occurred in zones apparently homogeneous suggests lateral variations in the mantle. Short period waves Li, Lg, Rg are recorded at LPB with a quite variable amplitude for the different South American provinces. Intermediate depth earthquake produce in LPB those phases as large as surface quakes do. The phase Li was studied especially for Peruvian earthquakes. In spite of structural complexity, a division of South America in zones (related to Flinn and Engdahl division) was attempted. Part (2). Attenuation of short period waves P, Li, Lg, Rg has been calculated for Peruvian earthquakes recorded at LPB. Provisory conclusions are in press in Revista Geofisica. Part (3). At the end of the reported period improvement of the knowledge of attenuation and P wave residuals is under study.


Descriptors :   *PLATE TECTONICS , *EARTHQUAKES , DEPTH , REGIONS , PHASE , TIME , VARIABLES , VARIATIONS , SURFACES , RESIDUALS , SEISMIC WAVES , ATTENUATION , RECORDS , AMPLITUDE , SOUTH AMERICA , DIVISION , VELOCITY , SURFACE WAVES


Subject Categories : Seismology


Distribution Statement : APPROVED FOR PUBLIC RELEASE