HR: 17:10h
AN: U54B-04    [Abstracts]
TI: Seismogenic sources and crustal structure near the seismological station of Angra dos Reis (ESAR), southeastern region of Brazil
AU: Romero, T
EM: tatiana@iag.usp.br
AF: University of Sao Paulo, Rua do Matao, 1226 Geophysics Departament, Sao Paulo, SP 05508-090, Brazil
AU: * Berrocal, J
EM: berrocal@iag.usp.br
AF: University of Sao Paulo, Rua do Matao, 1226 Geophysics Departament, Sao Paulo, SP 05508-090, Brazil
AU: Fernandes, C
EM: celia@iag.usp.br
AF: University of Sao Paulo, Rua do Matao, 1226 Geophysics Departament, Sao Paulo, SP 05508-090, Brazil
AU: de Lima, M V
EM: marcus@iag.usp.br
AF: University of Sao Paulo, Rua do Matao, 1226 Geophysics Departament, Sao Paulo, SP 05508-090, Brazil
AU: dos Reis, E
EM: emerson@wdi.com.br
AF: University of Sao Paulo, Rua do Matao, 1226 Geophysics Departament, Sao Paulo, SP 05508-090, Brazil
AB: The seismological station of Angra dos Reis (ESAR) is operating since the end of year 2000 located near to the nuclear power plants of Angra dos Reis, in the southern portion of Rio de Janeiro state, southeastern Brazil. The main objective of ESAR is defining the level of seismic activity in the area where those plants are installed, using data from a broadband seismograph that operates in a 100 cps continuous format. Epicentral determination of local seismic events is done through the back azimuth calculated with the P wave amplitude in the three component seismograms, and epicentral distance induced from the S-P time difference. Crustal structure for relating the S-P time and epicentral distance was obtained through a seismic refraction experiment using controlled sources, complemented with a detailed study of crustal structure beneath ESAR using teleseimic data and the receiver function method processed in the time domain. Since the beginning of operation ESAR has detected many local and near regional seismic events with magnitude lower than m_b 4.0, most of them below m_b 2.0, and not included in the Brazilian Seismic Catalogue. Epicenters of those events are spread in both oceanic and continental areas, in some cases forming clusters of different size, some of them, especially those located in the continent could belong to explosions made in stone-quarry, whereas, clusters and isolated epicenters located in the oceanic area could belong to natural earthquakes. Two of these oceanic clusters, located in the continental platform, may belong to seismogenic sources that are active near ESAR, and need further study to define its nature.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Union [U]
MN: 2007 Joint Assembly