Between 190 and 1997, the Panamerican Institute of Geography and History carried out the project "Seismic Hazard in Latin America and the Caribbean". As part of this project an earthquake catalogue was compiled for the region. On the other hand, in June, 1997, the USGS and the MIDAS Consortium decided to jointly publish a seismicity map of the MIDAS region. Considering the completeness of the IPGH Catalogue and in coordination with one of the principal investigators, Dr. James Tanner (lmansinh@julian.uwo.ca), it was decided to use this catalogue as one of the principal data bases for the seismicity for the Caribbean Seismicity Map. Taking this step an additional step further, at the December, 1997 MIDAS meeting it was decided that the catalogue could be placed on line and updated with the data provided by the participating networks. The region covered by the catalogue is 5°S to 33°N and 55°W to 120°W. Below we include the Summary for the Catalogue of the IPGH project (Tanner, J.G., Shepherd, J. B., 1997. Project Catalogue and Seismic Hazard Maps, Seismic Hazard in Latin America and the Caribbean, Panamerican Institute of Geography and History, Vol. 1, 143 pp).
The agencies (UNAM for Mexico, CERESIS for South America, CEPREDENAC for Central America and UWI for the Caribbean) from each of the four regions comprising the project (in addition to IPGH) have assembled revised catalogues of historical and instrumentally recorded seismicity. Each has been incorporated into a project catalogue, following guidelines set down by the Steering Committee, with the aid of software specially written for the purpose by the Geophysics Commission of IPGH.
As this catalogue is intended primarily for use in the computation of estimates of ground motion (velocity and/or acceleration), considerable time and effort was spent on the problem of multiple solutions to the same event. Time- and space-based windows of varying sizes were placed on the events in the catalogue and each pair of events identified by the software was examined to determine whether or not both represented solutions to the same event. In cases of duplicated solutions one was identified as the primary solution (an asterisk in column 1) and the other(s) as secondary (a blank in column 1). According to the policy of the Steering Committee, regional solutions to events were given preference unless there was good reason to proceed otherwise.
The original catalogue compiled by this extensive and time-consuming procedure contained over 100,000 unique events distributed over the geographic area bounded by 60°S, 33°N, 30°W and 120°W covering a period ranging from 1471 to the middle of 1994. Approximately one-half of the events contained at least one magnitude estimate of some type, the remainder serving as information useful in defining patterns of seismicity. About 2600 of these events are regarded as historical, having occurred prior to 1900. Finally, the formats adopted for the catalogue is that used by the International Seismological Centre (ISC) in the United Kingdom and the SISRA format (created by CERESIS for the original compilation of the earthquake catalogue for South America) used most commonly for data exchange among the groups involved in the project.
Considerable thought has gone into which magnitude type might best serve the seismic hazard calculations. At a meeting in 1993 the Steering Committee recommended the use of Ms for this purpose, but subsequently a decision was taken to use of moment magnitude (Mw) to be consistent with the Global Seismic Hazard Project (GSHAP) being undertaken under the aegis of International Lithosphere Program as part of the UN's International Decade for Natural Disaster Reduction. Accordingly, some 1200 moment magnitudes for events in the project area have been taken from various sources to establish a scale for estimating moment magnitudes of other types (Ms and mb). A second catalogue has been derived which contains moment^M magnitudes (originaland estimated) as the primary magnitude estimate.
Both the original and derived catalogue have been extensively tested resulting in a number of improvements in them. One of these tests has been the computation of seismic hazard estimates using a method, which is extremely fast on a computer, specially developed for the purpose. This method has proved so successful that the Steering Committee recommended it use for the computation of a "reference level" map for the project area.