Deep structure of the Baikal rift zone revealed by joint inversion of gravity and seismology

C Tiberi (1, 2) , M Diament (3) , Jacques Déverchère (4) , C Petit-Mariani (2) , V Mikhailov (5) , S Tikhotsky (5) , U Achauer (6)

1 Department of Geology, Royal Holloway
2 LT - Laboratoire de tectonique
3 IPGP - Institut de Physique du Globe de Paris
4 Laboratoire de géodynamique sous marine
5 IPE - Schmidt United Institute of Physics of the Earth [Moscow]
6 IPGS - Institut de physique du globe de Strasbourg

[1] The question of plate boundary forces and deep versus shallow asthenospheric uplift has long been debated in intracontinental rift areas, particularly in the Baikal rift zone, Asia, which is colder than other continental rifts. As previous gravity and teleseismic studies support the dominance of opposing mechanisms in the Baikal rift, we reconsidered both data sets and jointly inverted them. This more effective approach brings insight into location of the perturbing bodies related to the extension in this region. Our new joint inversion method allows for inverting the velocity-density relationship with independent model parametrization. We obtain velocity and density models that consistently show (1) crustal heterogeneities that coincide with the main tectonic features at the surface, (2) a faster and denser cratonic mantle NW of Lake Baikal that we relate to the thermal contrast between old and depleted Archean (Siberian platform) and Paleozoic orogenic belt (Sayan-Baikal belt), (3) three-dimensional topographic variations of the crust-mantle boundary with well-located upwarpings, and (4) the lithosphere-asthenosphere boundary uplift up to 70 km depth with a NW dip. Our resulting velocity and density models support the idea of a combined influence of lithospheric extension and inherited lithospheric heterogeneities for the origin of the Baikal rift zone. INDEX TERMS: 1234 Geodesy and Gravity: Regional and global gravity anomalies and Earth structure; 7218 Seismology: Lithosphere and upper mantle; 8122 Citation: Tiberi, C., M. Diament, J. Déverchère, C. Petit-Mariani, V. Mikhailov, S. Tikhotsky, and U. Achauer, Deep structure of the Baikal rift zone revealed by joint inversion of gravity and seismology,

Mots clés: Tectonophysics: Dynamics; gravity and tectonics; 8180 Tectonophysics: Evolution of the Earth: Tomography; KEYWORDS: joint inversion; gravity; seismology; intracontinental rift; lithospheric structures; Baikal rift zone

Domaines: Planète et Univers [physics]

C Tiberi, M Diament, Jacques Déverchère, C Petit-Mariani, V Mikhailov, et al.. Deep structure of the Baikal rift zone revealed by joint inversion of gravity and seismology. Journal of Geophysical Research : Solid Earth, 2003, 108 (B3), pp.2109. ⟨10.1029/2002JB001880⟩. ⟨insu-01356068⟩