Abstract

We present results from a regional study of ground-motion scaling parameters in central Mexico using data from a short-period vertical-component network and two broadband stations within the valley of Mexico. A total of 1220 waveforms recorded between 1994 and 2001 are used for the analysis. A damped least-squares regression using a simple model to separate the excitation, site, and propagation effects for the peak velocities in selected narrow-bandpass frequencies was carried out. The propagation term was parameterized to define a piecewise continuous geometrical spreading function, a frequency-dependent Q (f), and a distance-dependent duration that are consistent with the random vibration theory. We measured the average attenuation of S and Lg waves. A final model with a quality factor of Q(f) = 180f0.66 and a geometrical spreading of  
\[g(r)=\begin{array}{ll}r^{-1}&0{<}r{\leq}100\\r^{-0.2}&100{<}r{\leq}150\\r^{-0.5}&150{<}r{\leq}300\end{array}\]

is used for the parameterization of the ground-motion scaling. We find that this region is characterized by a rapid decay of ground-motion amplitude with distance, similar to that in other tectonically active regions.

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