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BOLETÍN DE LA SOCIEDAD GEOLÓGICA MEXICANA http://dx.doi.org/10.18268/BSGM2009v61n3a4 |
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3D velocity structure around the source area of the Armenia earthquake: 25 January 1999, Mw=6.2 (Colombia)
Velocidad estructural 3D alrededor del área fuente del sismo de Armenia del 25 de Enero de 1999, Mw=6.2 (Colombia)
Carlos Alberto Vargas–Jiménez1,*y Hugo Monsalve–Jaramillo2
1 Departamento de Geociencias. Grupo de Geofísica, Universidad Nacional de Colombia. Bogotá, Colombia.
2 Facultad de Ingeniería. Grupo Quimbaya, Universidad del Quindio. Armenia, Colombia.
* This email address is being protected from spambots. You need JavaScript enabled to view it..
Abstract
Selected P wave arrival time data of 518 events (mainly aftershocks) of the 25 January 1999 Armenia Earthquake (Mw=6.2, Colombia), recorded by 23 temporary seismic stations during February, 1999 to July, 2001, have been inverted simultaneously for both hypocenter locations and three–dimensional Vp structure. The surface geology of this area suggests a complex disposition of tectonic flakes composed by diverse rocks and crossed by the Romeral Fault System (RFS). However, there is a good correlation between high–velocity zones and old oceanic rocks affected by plutonic rocks. Metamorphic belts that wrap these rocks are well correlated with low–velocity zones. The disposition of tectonic flakes in depth is solved with a flower structure where the Cordoba fault slipped in a contact between high– and low–density rocks during the Armenia earthquake. The low–velocity zones would correspond to the older rocks that constitute the nucleus of the Central range. We infer that the source volume of the Armenia earthquake sequence lies within 75.64° – 75.72° W, 4.38° – 4.52°N and a depth of 5 – 21 km; the source volume is approximately 2 200 km3. Most of the well–located aftershocks occurred above the hypocenter of Armenia earthquake.
Key words: Local earthquake tomography, Armenia (Colombia), seismotectonic, Crust structure.
