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

1.35
later investigation and for the determination of the seismic risk of the
southamerican andean region. With these general objectives, Colombia proceded-
in the-firstplace-, toup-date tf is ig ofitssoand- i i events,
to analyze and process the data from the seismograms of alli)of i.s stations;
in the second place, to systematize the several seismic list ngs Iii accordance
with the norm adopted for all of the countries; third, to complete( as much
as possible the material concerning historical events and, finally,, to prepare
the catalog of intensities for a great number of earthqu)akes, of use for
ti, preparation of maps of isoseismal curves, and on that basis, the map of
171 intensities for Colombia. Colombia was able to present not only its
catalog of hypocenters and intensities but also a number of individual maps
with isoseismal curves, from which the map of maximum intensities was prepared.
A neotectonic map and maps. of landslides and soil liquefaction produced
by earthquake, were also prepared.
METHODS EMPLOYED IN THE DEVELOPMENT OF THE CATALOG OF HYPOCENTERS AND.
INTENSITIES
a) Naturally, the values of the parameters of historical earthquakes
can not, in general, be very precise, specially when there is no data to define
the intensity and the extension of the effects. The determination of
intensity depends considerably on reliability of the original source and the
appreciation of the intensity from the damage and effects observed by witnesses
quoted in the source. Not always can the data be accepted as exact, with
regard to the hour and minutes indicated in the sources; many times, there
are differences between the testimonies concerning the time of origin and
even the date, specially when the information is not directly from witnesses.
In the past, the reports were not too concerned about the precision of the
time of occurrence of the seismic events. Thus the time of origi, which has
been assigned to historical earthquakes must be taken as an acceptable figure
for each case, according to the available data.
b) For the same reasons, the values adopted for the parameters of location
for most of the historical cases, are of no greater value and significance
than a general indication of the region where the earthquake was Kfelt
or caused damage. The method followed by F. Ramirez in his catalog consisted
in locating the epicenter of an earthquake in the city where the effects and
damages were the greatest, if there was no data from other places. In the
case of reports of damages and effects approximately equal in two different
cities, the epicenter was located mid-way between them; if the damages and
effects were greater in one city than in the other the epicenter was located
at a distance inversely proportional to such effects. Naturally, the errors
of location can be considerable and it is not possible to determine the mag- -
nitude, specially when there is so little data, as is the case with the older
earthquakes.
c) For instrumental seismic events, the values of the parameters are
determined by persons and institutions which analyze seismograms and are cre-.
dited as the authors; in the case that some of these values are also determi.
ned by other persons or different institutions, this is indicated. For instrumental
events analyzed and processed by F. Ram'rez, or under his supervi
sion, and by personnel of the Instituto Geof'sico CIGE) the determination of
the parameters for time of origin, distance and geographic coordinates is