Abstract

MONSALVE MEJIA, GASPAR; VILLARRAGA MORALES, CAROLINA  and  IDARRAGA VALLEJO, JOHN EDWIN. INFERENCES ABOUT THE SEISMIC STRUCTURE OF THE UPPER LITHOSPHERE BENEATH THE ABURRÁ VALLEY USING DATA FROM ACCELEROMETER NETWORKS. Bol. cienc. tierra [online]. 2010, n.28, pp.77-94. ISSN 0120-3630.

It is known that the Earth´s crust under the city of Medellín and the Aburrá Valley consists primarily of a metamorphic basement intruded by calc-alkaline igneous bodies. However, there is no recollection of seismic models that allow for the evaluation of the geometric configuration of the different geologic bodies in depth. Using data from seismometers of the Colombia National Network (RSNC) and accelerometers of the Medellín and Aburrá Valley networks (RAM and RAVA) it is possible to infer some very general features about the seismic structure of the upper lithosphere beneath the Aburrá Valley. P and S wave arrival differential time data, registered at different stations in the Valley, suggest great lateral and vertical heterogeneity in the upper lithosphere, and great amounts of calc-alkaline igneous material within the crust, in consistent intercalation with the metamorphic basement, even beneath locations where no outcrops of igneous rocks are reported. Waveforms of the seismic records are consistent with vertical heterogeneity.  In general, the few available seismic data suggest that the amount of igneous material within the upper crust is greater than indicated in previous conceptual models of geometrical distribution of geologic bodies in the crust (Chica et al., 2003).

Keywords : Residual Time; Seismic Phase Arrival; Accelerometer; Seismic Velocity; Valle de Aburrá; Antioquia; Colombia.

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