Multiple SCS travel times and attenuation beneath Mexico and Central America

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Abstract
Multiple ScS phases recorded for the June 19, 1982 El Salvador earthquake (Ms = 7.0) are analyzed to determine whole mantle attenuation and upper mantle travel time anomalies beneath Mexico, Central America and northern South America. Recordings from the ultra long‐period seismographs at Pasadena and Berkeley and the SRO station ANMO provide eight ScSn arrivals with 15 bouncepoints concentrated within Mexico. The whole mantle QScS for these paths is estimated as 145 ± 27 in the frequency range 8 to 40 mHz, and the average ScSn+1−ScSn JB residual (ΔTScS) at a period of 50 sec is +1.5 sec. Eight ScSn phases of similar periods recorded at GDSN stations in South America yield a QScS estimate of 232 ± 89 and ΔTScS = −3.9 sec for paths beneath Central America, and QScS = 93 ± 17 and ΔTScS = +0.3 sec for paths beneath northern South America. These results indicate that the variations in travel times and attenuation beneath continental regions are as pronounced as differences reported between old oceanic and stable shield regimes.
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