A view of South and Central America from the International Seismological Centre

Abstract

Until now the study of seismicity in the region of South and Central America has been hindered by the very uneven distribution of stations and the lack of communication among agencies within the region and outside. There is thus a very uneven detection of earthquakes, which adds to uncertainty in estimation of seismic hazard. The reporting can also be very uneven in time, an example being a burst of reporting from Colombia for several months in 1991, resulting in greatly enhanced detection there for that period. There is now much regional · co-operation in Central America, and a new data centre collects readings from six regional countries and determines origins for about a hundred earthquakes a month, greatly improving the seismological coverage of this area. As might be expected, early in its operation some earthquakes appear seriously mislocated. The densest network currently reporting in South America is that around Santiago in Chile, resulting in the seismicity of this area being well documented. Close earthquakes are well located, but as is common in subduction areas, earthquakes outside the network tend to be located too deep. There are many instances here in which the depth determined by the Chilean agency is deep, but closer Argentinian stations show that the focus must be shallower. As equipment becomes more uniform and regional co-operation improves, the current seismological record for this region should become more reliable and capable of providing better assessments of seismic hazard.