Impulse Response from Seismic Interferometry and Earthquake Simulations

Thursday, 18 December 2014
Alan Juarez and Leonardo Ramirez-Guzman, Institute of Engineering-UNAM, Mexico, Mexico
We study the Green´s function (GF) retrieval based on the cross-correlation of numerically generated signals and its application to tomographic studies in central Mexico. The GF between two receivers is typically obtained based on the cross-correlation of noise recorded in two stations. Nevertheless, in this research we use large-scale earthquake numerical simulations to construct appropriate signals and optimal linear combinations of the displacements at two stations due to a small number of double-couple sources in a layered media to retrieve the Green´s function between receivers. The impulse response is obtained successfully by applying the cross-correlation, following standard interferometry theory. Additionally, the azimuthal dependence on the cross-correlations as an estimate of the impulse response is discussed using specific source locations. The main objective of our research is to elucidate the applicability of seismic interferometry in order to extend the frequency range and quality of tomographic studies based on observed regional earthquake records and dispersion maps. Thus, we show the results of the GF obtained using the aforementioned procedure in a realistic three-dimensional model of central Mexico, and quantify the discrepancies against the exact numerically computed GF. We conclude that a fair recovery is achieved by inverting velocity profiles at selected stations.