masterThesis
Sismicidade do sistema transformante de São Paulo, no Atlântico Equatorial, de janeiro - julho de 2013
Fecha
2019-10-25Registro en:
DE MELO, Guilherme Weber Sampaio. Sismicidade do sistema transformante de São Paulo, no Atlântico Equatorial, de janeiro - julho de 2013. 2019. 116f. Dissertação (Mestrado em Geodinâmica e Geofísica) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2019.
Autor
De Melo, Guilherme Weber Sampaio
Resumen
The Equatorial Atlantic is formed by several slow-slipping ridges and
transform faults also associated with inactive fracture zones. Among these, the
St. Paul Transform System (SPTS) is a complex multi-fault with four faults and
three intra-transform segments with a long-offset of 630 km. In the northern
transform, the 200 km long and 30 km wide Atobá Ridge is a major topographic
feature that reaches the sea level at the St. Peter and St. Paul Archipelago
(SPSPA). We have determined the hypocentral location of 62 minor-moderate
earthquakes of SPTS. The earthquakes occurred in 2013 and were recorded by
a seismometer installed in SPSPA and three hydrophones deployed during the
COLMEIA cruise. A seismogenic zone with a deep brittle-ductile transition was
identified in SPTS, with hypocenters reaching 18 km beneath the seafloor. We
observed that this lithospheric structure presents relation with the offset age and
controls the maximum hypocentral depths of oceanic transform faults. Besides,
the earthquakes indicated the existence of a broad serpentinization depth
reaching 18 km beneath the Atobá Ridge. We interpreted this as an effect of
deep-water percolation into the mantle in the SPTS, which cause a fluid-mantle
rocks interaction and allowed the growth of faults into the mantle. Some
hypocenters were in the central fracture zone (CFZ) segment of SPTS and their
depths reached 8.8 km beneath the seafloor. We interpreted this seismicity as
reactivation of a weakness zone existent in CFZ, which occurred due to the
transpressive load-induced stress from the Atobá Ridge.