3D Velocity Structure around the Source Area of the Armenia Earthquake: 25 January 1999, Mw=6.2 (Colombia)

Resumen

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 75.64º
- 75.72º W, 4.38º - 4.52ºN 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.