Enhanced Rayleigh waves tomography of Mexico using ambient noise cross-correlations (C1) and correlations of coda of correlations (C3)

Abstract:

Standard application of the seismic ambient noise tomography considers the existence of synchronous records at stations for green’s functions retrieval. More recent theoretical and experimental observations showed the possibility to apply correlation of coda of noise correlation (C₃) to obtain green’s functions between stations of asynchronous seismic networks making possible to dramatically increase databases for imagining the Earth's interior. However, this possibility has not been fully exploited yet, and right now the data C₃ are not included into tomographic inversions to refine seismic structures. Here we show for the first time how to incorporate the data of C₁ and C₃ to calculate dispersion maps of Rayleigh waves in the range period of 10-120s, and how the merging of these datasets improves the resolution of the structures imaged.

Tomographic images are obtained for an area covering Mexico, the Gulf of Mexico and the southern U.S. We show dispersion maps calculated using both data of C₁ and the complete dataset (C₁+C₃). The latter provide new details of the seismic structure of the region allowing a better understanding of their role on the geodynamics of the study area. The resolving power obtained in our study is several times higher than in previous studies based on ambient noise. This demonstrates the new possibilities for imaging the Earth’s crust and upper mantle using this enlarged database.