Application of Spectral Decomposition approach to examine the attenuation, source parameters, and site effects in Madagascar

A spectral decomposition approach is applied to separate the site amplification, path attenuation, and source parameters of earthquakes that occurred in Madagascar between 2011 and 2013. Concerning source parameters, the stress drop is derived from the source spectra, fitting the Brune model. Our findings indicate an increase in stress drop with magnitude, ranging from 0.001 to 0.1 MPa. Additionally, the results unveil a consistent attenuation curve diminishing with distance, characterized by a swift decay at higher frequencies below the 1/R^2 decay function. The frequency-dependent behavior of the estimated quality factor for S waves suggests rapid damping and slow dissipation.Regarding site amplification, a robust agreement is noted between resonance frequency obtained through GIT and the H/V spectral ratio. Furthermore, we explore the correlation between site amplification and geological characteristics such as sediment depth and lithology.