Accession Number : AD0020539


Title :   BERMUDA T PHASES WITH LARGE CONTINENTAL PATHS


Descriptive Note : Technical rept. no. 30


Corporate Author : LAMONT GEOLOGICAL OBSERVATORY PALISADES NY


Personal Author(s) : Shurbet, D H


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/020539.pdf


Report Date : Aug 1953


Pagination or Media Count : 21


Abstract : Results are presented from an investigation of earthquakes of magnitude greater than 6 1.2 occurring in southern Mexico, Central America, and South America since the installation of Benioff short-period seismographs on Bermuda in 1951. Selected Benioff short-period vertical records from the San Juan station were also used in the investigation. A short-period arrival on records of the Bermuda-Columbia Seismograph Station is identified as the T phase. The following conclusions were reached i the study of T phases generated by inland earthquakes; (1) the energy travels as P before entering the water, and the S phase is not an effective generator of T at the Puerto Rico Scorp; (2) a deep-focus earthquake is a better generator of this T phase; (3) both magnitude and frequency of the P phase are critical in determining whether it will generate a T phase a T phase upon its arrival at a steep submarine slope; (4) a T phase will be generated by the arrival of a P phase at a steep submarine slope if the P phase contains energy within the characteristic frequency range of the T phase, and this T phase can be detected at distant stations if there are no obstacles in the path between the submarine slope and the station; (5) the P-T transmission could have been predicted by considerations of reciprocity from earlier observation at inland stations; and (6) background noises in the Sofar channel arise in some cases from earthquakes as much as several thousand miles inland.


Descriptors :   *SEISMOLOGICAL STATIONS , *EARTHQUAKES , *SEISMIC WAVES , PHASE , SHORT RANGE(TIME) , SLOPE , ARRIVAL , SUBMARINES , BACKGROUND NOISE , SOUTH AMERICA , MEXICO , PUERTO RICO , CENTRAL AMERICA , ENERGY , BERMUDA , WATER , OBSERVATION


Subject Categories : Seismology


Distribution Statement : APPROVED FOR PUBLIC RELEASE