Crustal thickness estimation beneath the Northern Andes (Colombia) from teleseismic receiver functions

The recent presence of broadband seismic stations in Colombian territory, as a part of the Colombian Seismological Network, operated by the Colombian Geological Survey, has provided new data for crustal thickness estimation beneath the Northern Andean region. We calculated P to S radial and transverse teleseismic receiver functions at 18 stations in Colombia, for earthquakes at epicentral distances between 29 and 91 degrees, occurred between 2008 and 2012. The deconvolution was calculated in the time domain, aiming for at least a 70% resemblance between the convolution of the receiver function and the vertical seismogram, and the radial/transverse seismogram. In Northern Colombia, at the Sinu Valley, receiver functions show a clear conversion, indicating a crustal thickness of around 29 km; at stations in the Upper and Middle Magdalena Valley, between the Central and Eastern Cordilleras, crustal thickness should be between 40 and 44 km, similar to what was obtained for the Central Cordillera beneath the Ruiz Volcano. Stations at other volcanic areas on the Central Cordillera do not show a consistent Moho conversion and require more work on interpretation. Receiver functions at a station at the craton in South East Colombia, near the foothills of the Eastern Cordillera, clearly indicate the presence of the Moho discontinuity at a depth near 36 km. Receiver functions from seismometers on the Eastern Cordillera near Bogota do not show a consistent signal of a P to S conversion that can be unequivocally interpreted as the effect of the Moho discontinuity, and there are conversions that suggest the existence of major crustal discontinuities; there seems to be strong effects of dipping interfaces, anisotropy and/or lateral heterogeneity that still remain to be evaluated. These features are possibly associated with the fold and thrust belt developed in the Eastern Cordillera of Colombia, which has generated a very complex crustal architecture.