The December 26th 2004 Tsunami Recorded along the Southeastern Coast of Brazil

Sea level measurements along the southeastern Brazilian coast, between 20° S and 30° S, show the effect of the Sumatra Tsunami of December 26, 2004. Two records from stations, one located inside an estuary and other inside a bay, shows oscillations of about 0.20 m range; one additional record from a station facing the open sea shows up to 1.2 m range oscillations. These oscillations have around 45 min period, starting 20–22 h after the Sumatra earthquake in the Indian Ocean (00:59 UTC) and lasting for 2 days. A computer modelling of the event reproduces the time of arrival of long shallow-water tsunami waves at the southeastern Brazilian coast but with slight longer period and amplitudes smaller than observed at the coast, probably due to its coarse resolution (1/4 of a degree). The high amplitudes observed at the coast suggest a mechanism of amplification of these waves over the southeastern Brazilian shelf.