Crustal structure of central Lake Baikal : insights into intracontinental rifting

This paper is not subject to U.S. copyright. The definitive version was published in Journal of Geophysical Research 107, B7 (2002): 2132, doi:10.1029/2001JB000300.The Cenozoic rift system of Baikal, located in the interior of the largest continental mass on Earth, is thought to represent a potential analog of the early stage of breakup of supercontinents. We present a detailed P wave velocity structure of the crust and sediments beneath the Central Basin, the deepest basin in the Baikal rift system. The structure is characterized by a Moho depth of 39–42.5 km; an 8-km-thick, laterally continuous high-velocity (7.05–7.4 km/s) lower crust, normal upper mantle velocity (8 km/s), a sedimentary section reaching maximum depths of 9 km, and a gradual increase of sediment velocity with depth. We interpret the high-velocity lower crust to be part of the Siberian Platform that was not thinned or altered significantly during rifting. In comparison to published results from the Siberian Platform, Moho under the basin is elevated by <3 km. On the basis of these results we propose that the basin was formed by upper crustal extension, possibly reactivating structures in an ancient fold-and-thrust belt. The extent and location of upper mantle extension are not revealed by our data, and it may be offset from the rift. We believe that the Baikal rift structure is similar in many respects to the Mesozoic Atlantic rift system, the precursor to the formation of the North Atlantic Ocean. We also propose that the Central Baikal rift evolved by episodic fault propagation and basin enlargement, rather than by two-stage rift evolution as is commonly assumed.This project was jointly funded by the U.S. Geological Survey Coastal and Marine Program and the Russian Academy of Sciences

Архітектурне середовище та акустична безпека людини

The article shows main directions and assignments for working out and implementation of special «Program of safeguarding of acoustical security for Ukraine population».Рассмотрены основные направления и задачи для разработки и реализации специальной «Программы обеспечения акустической безопасности населения Украины».Багато сучасних фахівців, зокрема архітектори, соціологи, екологи і т. д. називають міста «трущобами сьогоднішнього і завтрашнього дня», «центрами нервових захворювань і злочинності», «сучасними упорядженими концентраційними таборами», «клітками»... І це далеко не вимисел, а гірка реальність – розростання міст, нестача нормального житла, дефіцит життєвого простору, замах на навколишнє середовище, забруднення повітря і води, шум, сміття, поширення захворювань, нелюдськість, насильство, злочинність. Парадокс існування міст полягає в самому їх виникненні не велінням випадку, а історичною неминучістю відділення ремесла від землеробства, поглибленням суспільного поділу праці, виникненням регулярного товарообміну. Помилка сучасності – забуття тієї простої істини, що місто повинне існувати для людини, забезпечуючи всі потреби суспільства і захищаючи людей. «Місто повинне бути побудоване так, щоб забезпечити своїм мешканцям безпеку і щастя» – цією геніальною фразою великого мислителя Аристотеля необхідно починати і закінчувати трудовий день кожному городянину, від домогосподарки до мера міста. Жодне рішення, дія чи захід, що суперечать даному гаслу, не повинні мати права на життя, незважаючи ні на які економічні труднощі

Palaeozoic orogeneses around the Siberian craton: Structure and evolution of the Patom belt and foredeep

International audienceThis paper sheds light on the evolution of the Patom belt. This mountain range draws an arc along the southeastern edge of the Siberian craton. It is supposed to be of Caledonian age and to result from the accretion of microcontinents against the craton, but up to now, its detailed stratigraphic and tectonic history was unclear. A field study allows us to clarify it. The sedimentary record is marked by a slow evolution with stable periods of more than 250 Ma. The observed sedimentary succession confirms the existence of a passive margin setting in the late Riphean (900 Ma), followed during the Vendian (650-600 Ma) by the obduction of the Baikal-Muya ophiolites belt and a foredeep inversion. After that, a Late Cambrian extension occurred, which is first described in this paper. The second collision stage occurred after 385 Ma, in the Late Devonian-Early Carboniferous. Sedimentary and tectonic data are interpreted in the light of the geodynamic evolution of Siberia, which is dominated by continental collages against the Siberian craton. Field data reveal a homogeneous direction of compression from the inner areas to the foreland. Whereas the inner range displays metamorphosed units deformed in the ductile domain, deformation is weaker in the foreland, which developed above the cratonic crust.We relate this high deformation gradient to the presence of the stiff craton which impeded strain propagation. The irregular shape of the craton as well as preexistent basement topography can explain the different tectonic styles observed along the belt

Deep structure and mechanical behavior of the lithosphere in the Hangai-Hovsgol region, Mongolia : new constraints from gravity modeling

Earth and Planetary Science Letters, v. 197, n. 3-4, p. 133-149, 2002. http://dx.doi.org/10.1016/S0012-821X(02)00470-3International audienc

Height of faceted spurs, a proxy for determining long-term throw rates on normal faults: Evidence from the North Baikal Rift System, Siberia

International audienc

The 1999M_w 6.0 earthquake sequence in the southern Baikal rift, Asia, and its seismotectonic implications

The 1999 February 25 earthquakeis the largest event to have occurred in the Baikal rift system since the 1959earthquake. This earthquake sequence took place in the southern basin of Lake Baikal, a region characterized by a sharp transition from strike-slip faulting on the Main Sayan Fault to normal faulting along the border faults of the lake. Thanks to the development of the regional network and a temporal station installed after the main shock, we performed a relocation of the aftershocks to describe the rupture area and to determine fault-plane solutions. We show that the main shock was caused by normal faulting on an intrabasin fault striking northeast and steeply dipping to the northwest. Aftershock hypocentres did not cluster at the same depth but were spread from 5 to 25 km depth. Stress inversion carried out using focal mechanisms of the sequence reveals a radial extensive stress regime with a minimum principal stress axis(N155°E) slightly oblique to the regional stress field (N139°E), which depicts a stronger intermediate-axis. This behaviour suggests transient stress perturbation induced by the main shock in the neighbouring zones of the rupture. Strain release deduced from GPS data and historical seismicity shows that within the southern tip of the Baikal rift basin, a significant stress release has occurred for at least two centuries, probably through active normal faulting shared among several faults, while the Main Sayan strike-slip fault further west was undergoing interseismic strain accumulation