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

Abstract

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 350º-10º. 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.

Tidal Coulomb Failure Stresses in the northern Andean intermediate depth seismic clusters: Implications for a possible correlation between tides and seismicity

“…They do not use the TCFS criterion in their study. Moreover, and as we argued in our recent work (Moncayo et al, 2019), tidal phases have been improperly computed, especially in the case of the diurnal and monthly phases, in such a way that in most cases, including probably that of Cadicheanu et al (2014), the strong diurnal and monthly correlations we have observed, have been mostly absent. This paper is organized as follows: in Section 2 we start by describing the tectonic setting of the analyzed areas.…”

“…The Cauca seismic cluster is likely related to the subduction of Nazca beneath the North Andean Block (Cortes and Angelier, 2005;Chang et al, 2017). An in-depth analysis of the potential correlation between seismicity and earth tides in those clusters was carried out recently by Moncayo et al (2019), finding anomalously low values of the Schuster test p-values for the diurnal and monthly tidal components. Those findings motivated this follow-up investigation.…”

“…In a previous work, we reported the discovery of correlation anomalies (anomalously low p-values of the Schuster Statistical Test) between intermediate depth seismicity in the Bucaramanga nest and Cauca cluster in Colombia (Moncayo et al, 2019) and the diurnal and monthly phase of the body tides. In that study, we neglected the indirect effect of OTL arguing that typical distances of the seismic clusters to the Caribbean and Pacific coasts were relatively large (200-500 km).…”

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A recent statistical analysis of the relationship between tides and seismic activity in Colombia has suggested the existence of correlation anomalies for the case of intermediate depth events in the Bucaramanga nest and the Cauca cluster (Moncayo et al, 2019). In this work, we explore in detail the hypothesis that tides may be triggering seismic activity in these regions and extend the analysis to two other seismic clusters in northern-central South America, specifically in the areas of El Puyo (Ecuador) and Pucallpa (Peru).

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“…Moreover, we take a step further by including in our analysis other two areas of high seismicity rate, close to the West Coast of South America, namely the El Puyo (Ecuador) and Pucallpa (Peru) seismic swarms, where a noticeable concentration of intermediate-depth events has been observed (Zarifi and Havskov, 2003;Soles Valdivia, 2012;Taipe Acosta, 2013). In Moncayo et al (2019) we focused on devising novel approaches to compute the tidal phases and to perform the statistical analysis of their correlation with seismicity. In that study, we applied our methods to samples of earthquakes with a statistically significant number of events.…”