  We present the first systematic exploration of earth tides-seismicity
correlation in northwestern South America, with a special emphasis in Colombia.
For this purpose, we use a dataset of ~167,000 earthquakes, gathered by the
Colombian Seismological Network between 1993 and 2017. Most of the events are
intermediate-depth earthquakes from the Bucaramanga seismic nest and the Cauca
seismic cluster. For this purpose, we implemented a novel approach for the
calculation of tidal phases that considers the relative positions of the
Earth-Moon-Sun system at the time of the events. After applying the standard
Schuster test to the whole dataset and to several earthquake samples
(classified by time, location, magnitude and depth), we found strong
correlation anomalies with the diurnal and monthly components of the tide
(global log(p) values around -7.0 for the diurnal constituent and -12.1 for the
monthly constituent), especially for the intermediate depth events. These
anomalies suggest that around 16% of the deep earthquakes in Colombia may be
triggered by tides, especially when the monthly phase is between
350$^\circ$-10$^\circ$. We attribute our positive results, which favor the
tidal-triggering hypothesis, in contrast to previous negative ones to: 1) the
size of our dataset, and 2) the method we used to calculate tidal phases.
Anyone willing to reproduce our results or to apply our methodology to custom
datasets can use the public information system tQuakes that we developed for
this work.
