ATTENUATION MODELS FOR A COLOMBIAN LLANOS FOOTHILLS AREA USING ATTENUATION OF CODA WAVES

Abstract

Prominent seismic activity near to the Colombian Llanos Foothills was used for estimating the coda waves’ attenuation in order to get a better understanding of the geological and structural setting of study area. The values of coda attenuation (Qc-1) were calculated by the Single Isotropic Scattering model - SIS proposed by Sato (1977) with the purpose of evaluating their spatial distribution and relationship with the geological structure of the crust. In this work were used about 4,000 earthquakes with ML > 1.7 that were recorded by the ColombianNational Seismological Network between 1993 and 2012. We used the SEISAN software by detecting the main seismic phases, then fltered in band pass centered on 2 (1-3) Hz, 8 (5-11) Hz, 12 (8-16) Hz, 16 (10-22) Hz and 25 (17-33) Hz to fnally get the quality coda waves factors (Qc) and the power law parameters Q0= 31.74 and ƞ = 0.92. Subsequently the results were plotted using Spatial inversion technique and with these map of anomalies, comparing the tectonic setting as well as the lithological and geothermal anomalies. Finally it was observed a dependence between Q0and ƞ values with areas where is observed active tectonics.