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Contemporary horizontal movements and seismicity of the south Baikal Basin (Baikal rift system) |
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| Authors: | V A Sankov A V Lukhnev A I Miroshnitchenko A A Dobrynina S V Ashurkov L M Byzov M G Dembelov E Calais J Déverchère |
| Institution: | 1. Institute of the Earth Crust, Siberian Branch, Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia 2. Irkutsk State University, bul’v. Gagarina 20, Irkutsk, Russia 3. Institute of Physical Material Science, Siberian Branch, Russian Academy of Sciences, ul. Sakhyanovoi 8, Ulan-Ude, 670047, Russia 4. Ecole Normale Supérieure, Paris, France 5. Université de Bretagne Occidentale, Brest, France |
| Abstract: | The contemporary horizontal movements and deformations in the central and southern parts of the Baikal depression are analyzed, and their relationship with contemporary seismicity is studied. Based on the long-term measurements by the Baikal geodynamical GPS monitoring network, the refined estimate is obtained for the velocity of the divergence of the Siberian and Transbaikalian blocks, which is found to occur in the southeastward direction (130°) at 3.4 ± 0.7 mm per annum. This agrees with the parameters of the long-term extension component estimated from the geological data and with the direction of extension determined from the seismic data. The distribution of the displacement velocity across the strike of the rift, which gradually increases from one block to another, suggests a nonrigid behavior of the continental lithospheric plates at the divergent boundary. About 30% (1.0–1.5 mm per annum) of the total increase in the velocity is accommodated by the Baikal Basin. The strain rate within the trough reaches 3.1 × 10?8 yr?1 and decreases on either side across the structure. The character of distribution of the horizontal displacement velocities on the Baikal divergent boundary between the Eurasian and Amurian plates favors the model of passive rifting. The zones of highly contrasting topography and increased seismicity are localized within the area of contemporary deformations, and the seismic moment release rate directly depends on the strain rate. Here, the rate of the seismic moment release rate makes up a few percent of the geodetic moment accumulation rate calculated by the approach suggested by Anderson (1979). Based on the coherence between the graphs of the rates of geodetic moment accumulation and seismic moment release rate by the earthquakes with M ≥ 5.0 during the historical and instrumental observation periods, the contemporary seismic hazard for the South Baikal Basin could be assessed at a level of seismic event with M = 7.5–7.6. |
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