Lithospheric structure of the Spanish Central System

AGU Fall Meeting 2019 in San Francisco, 9-13 december 2019
The Spanish Central System is an intraplate mountain range dividing the Iberian Inner Plateau in two sectors ¿ the Duero Basin (N) and, the Tajo Basin (S). The latter has an average altitude of 450-500 m while the former presents a higher average altitude 750-800 m. This intraplate orogen features a thick-skin pop-up and pop-down configuration formed by the reactivation of Variscan structures. Its high topography is the response of a tectonically thickened crust evidenced by 1) the geometry of the Moho discontinuity 2) an imbricated crustal architecture and/or 3) the rheological properties of the lithosphere. Research has been carried out to build a lithospheric-scale model across the orogen. A 400 km long multi-seismic transect has been acquired using natural and controlled source seismic data. The earthquakes and seismic noise data was acquired over a period of one to two months of continuous recording along a linear array (69 short-period seismic stations). The controlled source data included over 1000 stations and a series of acoustic sources. This effort has delineated the geometry of the base of the crust by: Global-Phase Seismic and, conventional noise interferometry, and, wide-angle imaging. The Global Phase approach used PK, PKiKP and PKIKP phases of earthquakes (> 120° epicentral distance). Stacking of the autocorrelations of these phases contribute to a pseudo zero-offset X-section. The application of ambient noise seismic interferometry complements the zero-offset reflection image, defining the geometry of the Moho. Further details on the lithospheric structure is provided by seismic wide-angle reflection images, which reveal a clear thickening of the crust below the Central System resulting, most probably, from an imbrication of the lower crust. Accordingly, the crust-mantle boundary is mapped as a relative flat interface at approximately 10 s two-way travel time except under the Central System, where this feature deepens towards the NW reaching more than 12 s. An intra-crustal boundary is well defined at 5 s. Reflectivity within upper-mantle depths is scattered throughout the profile, located between 13-18 s, and probably related with the Hales discontinuity. Funding resources: EU EIT-RawMaterials Ref: 17024_20170331_92304; MINECO: CGL2016-81964-REDE CGL2014-56548-P: JCYL: SA065P17)
Funding resources: EU EIT-RawMaterials Ref: 17024_20170331_92304; MINECO: CGL2016-81964-REDE CGL2014-56548-P: JCYL: SA065P17)