Teleseismic receiver functions imaging of Siberia

Friday, 19 December 2014
Mohammad Youssof, Hans Thybo and Irina M Artemieva, University of Copenhagen, Copenhagen, Denmark
We map the lithosphere in Siberia by using the available broadband seismic data for calculation of Ps- and Sp-wave receiver functions (RF). RFs show converted waves from discontinuities in the vicinity of the seismic stations. The main objective is to image the Moho and upper mantle discontinuities, including the lithosphere-asthenosphere boundary (LAB) beneath the study area. We construct the RF using the LQT method (Vinnik, 1977; Kind et al. 1995) in the version by Yuan et al. (1997). Rotation of ray coordinates uses the incidence angles predicted by the AK135 velocity model. This decomposes the wave-field into P, SV and SH components. Converted phases are isolated by iterative, time-domain spiking deconvolution with prewhitening to stabilize the filtering.

The RF model images the crustal thickness between 35 and 55 km with a rough Moho topography. Additionally, intracrustal structures are identified by high-frequency S-RFs. Teleseismic converted Ps waves have higher frequency content (0.5–2 Hz) than Sp, which have an upper frequency of 0.1–0.2 Hz, and therefore Ps have about an order of magnitude better resolving power than Sp. The converted Sp-wave rarely resolve intracrustal structure, but can be used for determining Moho depth, and are excellent for detecting relatively broad vertical gradients in velocity, such as expected for a thermally controlled LAB. The combination of both types of RFs allows for independent discontinuity models of the same area in different frequency bands using converted waves with very different raypaths. The two models are coupled through the velocity model used for depth imaging.

The results of RF analysis of the crustal and mantle structure will help to build a model for tectonic and geodynamic evolution of different provinces of Siberia. We compare our results to the recent detailed model of crustal structure in the whole of Siberia (SibCrust, Cherepanova et al., 2013) and with seismic models for similar geodynamic settings worldwide.