  We study long-range correlations and trends in time series extracted from the
data of seismic events occurred from 1973 to 2011 in a rectangular region that
contains mainly all the continental part of Colombia. The long-range
correlations are detected by the calculation of the Hurst exponents for the
time series of interevent intervals, separation distances, depth differences
and magnitude differences. By using a modification of the classical $R/S$
method that has been developed to detect short-range correlations in time
series, we find the existence of persistence for all the time series considered
except for magnitude differences. We find also, by using the $DFA$ until the
third order, that the studied time series are not influenced by trends.
Additionally, an analysis of the Hurst exponent as a function of the number of
events in the time and the maximum window size is presented.
