STRESS FIELD ESTIMATION FROM FOCAL MECHANISMS AND BACK PROJECTED IMAGES IN POTENTIALLY INDUCED SEISMICITY REGION, COLOMBIA

Abstract:

Over 156 earthquakes (Mw 2.8 - 4.4) were detected from April 2013 to December 2014 in Puerto Gaitán, eastern Colombia (Eastern Llanos Basin), where there were no earthquakes with this magnitude in the past. Earthquakes were detected by the National Seismological Network of Colombia (NSNC) and were used for modeling the track rupture front and orientation of the most energetic events. For these earthquakes, we applied a joint inversion method for estimating focal mechanisms in order to determine fault trends and the stress tensor in the area, which defines a maximum stress with Normal tendency. Focal mechanisms also represent in most of the cases Normal faults with NW orientation that match well with the tracking rupture deduced from the Back Projection Imaging modeling. This earthquake anomalous activity is taking place inside some oil fields. Based on spatial and temporal distribution of seismicity, as well our estimations, we hypothesize that this seismicity is induced by hydrocarbon operations are taking place in the study area.