catalogo de terremotos para america del sur catalog of earthquakes ...

locally which actually fell in Colc;:;ia. it is possible that the event was
deleted from both catalogs and so is not included anywhere ill the South
American catalog. In addition, both countries may have included the same
105
event, and this duplication may not have been discovered. Checking was done
to assure that large events (approximately M. > 7.5) have not been deleted or
duplicated. More extensive checking was not feasible in this phase of the
wor'.
Sorting out magnitude sources and scaleb also presented a number of
problems. Magnitudes are frequently reported with incomplete documentation by
various agencies. We have attempted to obtain a description of the method
used in the magnitude determination for all magnitudes included in the
catalog.
Magnitudes
A primary goal in the development of this catalog has been to present
magnitude data in a form which documents as well as possible how the
magnitudes were computed. This information is critical for many types of
research such as seismic hazard analysis. It is important that magnitude data
grouped together be homogeneous. For example, in reS.esslng intensity on
magnitude, if the magnitudes are a mixed group of mb and M s the regression
will be of little value. Many questions arise as to how to properly handle
magnitudes computed in different ways, but the first step In resolving this
problem is to be able to determine what methods were used for the data that
are included in the catalog. Therefore, for all magnitudes included in the
catalog, we have included references which describe how the values were
determined. Although magnitudes may be labeled with the same magnitude scale
code, they may be determined in different ways. For example, both GS and MOS