Local magnitude scale for the area of Paletará (Cauca, Colombia)
DOI:
https://doi.org/10.32685/0120-1425/boletingeo.44.2018.36Keywords:
local magnitude, Wood-Anderson seismograph, attenuation
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Abstract
The determination of the local magnitude scale (ML) for the Paletará zone (PZ), Colombia was performed for the first time by the inversion of the horizontal components of 2848 amplitudes at 18 seismic stations for VT and local tectonic earthquakes with focal depths less than 37 km and focal distances less than 220 km. The distance corrected function found in this study is
−log(Ao) = 1,3541 log(r/17) + 0,001639(r − 17) + 2,
where –log(Ao) is the empirically determined distance correction and r is the hypocentral distance. Accordingly, the local magnitude scale for PZ is defined as:
ML = log(Amm) + 1,3541 log(r/17) + 0,001639(r − 17) 2 + S,
or according to IASPEI formulation:
ML = log(Anm) + 1,3541 log(r) + 0,001639r − 2,37 + S
where Amm is the peak amplitude in mm simulated in a Wood-Anderson seismogram, Anm is the peak amplitude in nm simulated in a Wood-Anderson seismogram, with a magnification of 1, and S is the station correction due to differences in site amplification.
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