The 1986 1988 intraplate earthquake sequence near João Câmara, northeast Brazil—evolution of seismicity
Abstract
The 1986-1988 intraplate earthquake sequence near João Câmara (5.5°S, 35.7° W) has been among the most significant in northeast Brazil this century. Some 14,000 events were recorded in the 18 months from August 1986, including fifteen above magnitude 4.0 and one of 5.1; 4000 buildings were damaged. A local network of four portable seismographs was operated during most of the period, augmented by a nine station telemetric network between May 1987 and April 1988. The temporal and spatial distribution of this seismicity is examined and determination of unusually good hypocentres is made possible by the simple velocity structure, good signal transmission and impulsive P- and S-arrivals on most seismograms. Activity has been closely confined to a 28 km linear zone with a strike of 040 °, except for some small events along a parallel zone displaced laterally by 12 km. Neither zone has been related to any surface feature. Some unusual characteristics have raised concern about possible future seismicity: the largest event occurred four months after the onset of activity and after several weeks of relative quiescence. A 5 km intermediate section of the inferred fault has so far experienced only a few very small events.
- Publication:
-
Tectonophysics
- Pub Date:
- October 1989
- DOI:
- 10.1016/0040-1951(89)90062-0
- Bibcode:
- 1989Tectp.167..117T