Correlation between tides and seismicity in Northwestern South America: The case of Colombia

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°-10°. 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.