Abstract

SEPULVEDA-JAIMES, Francia Jullyette  and  CABRERA-ZAMBRANO, Francisco Henry. 3D seismic tomography in the seismic nest of Bucaramanga (Colombia). bol.geol. [online]. 2018, vol.40, n.2, pp.15-33. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v40n2-2018001.

Seismic tomography is a set of techniques used to obtain an image of velocity fields inside the Earth, using waves measurements. In this work, this technique was used to generate a quasi-3D velocity model of the P wave of Bucaramanga’s nest zone –a highly seismic zone in Colombia caused by the collision of the Caribbean and Nazca Plates under the South American plate, able to generate intermediate earthquakes (70 – 200km). For this research, 1223 earthquakes recorded by the seismic stations of “National Seismological Network of Colombia” were analyzed. They all occurred in Santander, Colombia, within 6° - 8°N and 72° - 74°W recorded from January 2012 to June 2016. Only 1138 events that met the seismic nest parameters –like latitude, longitude and depth – were used to generate a first 1D velocity model where only depth velocity variations were considered. Furthermore, a quasi-3D model with both horizontal layers of different depths and lateral variations was generated. Results show two continuous anomalies in the study zone: the first one, a negative one interpreted as partial melt of magma and, the second one, a positive anomaly interpreted to magma crystallization.

Keywords : seismic tomography; Seismic Nest of Bucaramanga; velocity model.

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