Resumo

VARGAS-JIMENEZ, Carlos Alberto  e  MONSALVE-JARAMILLO, Hugo. 3D velocity structure around the source Area of the Armenia earthquake: 25 January 1999, Mw=6.2 (Colombia). Bol. Soc. Geol. Mex [online]. 2009, vol.61, n.3, pp.339-351. ISSN 1405-3322.

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.

Palavras-chave : Local earthquake tomography; Armenia (Colombia); seismotectonic; Crust structure.

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