Depth distribution of earthquakes in the Baikal rift system and its implications for the rheology of the lithosphere

• DOI: 10.1046/j.0956-540x.2001.1484.484.x
• Publication Date: 2003-03-11T22:21:30Z
• Authors: Jacques Déverchère; Carole Petit; Nadejda Gileva; Natalia Radzimino...; Valentina Melnikova; Vladimir San'Kov
• Keywords: East African Rift

Abstract The correspondence between the predicted brittle–plastic transition within crust and maximum depth of earthquakes is examined in case Baikal rift, Siberia. Although little accurate information on depths available through large- moderate-size earthquakes, there are frequent indications foci at 20 km more. We have relocated 632 events recorded nearby stations that occurred 1971 1997, with epicentral uncertainties less than 5 km, over eastern southern parts rift. compared these results other distributions obtained previous studies from background seismicity NE rift (1365 Kalar-Chara zone 704 Muya region). relative abundance generally low 0 10 (7–15 per cent) high 15 25 (∼50 cent). Earthquake activity still significant 30 (9–15 persists 40 (7–13 Very few below Moho. use empirical constitutive laws to obtain yield-stress limits several layers made dominant lithologies examine whether observed distribution (519 controlled by a close station located extensional domain system) can match crustal strength proportion deeper brittle–ductile crust. A good fit using quartz rheology 0–10 diabase 10–45 moderate temperature field which corresponds ∼100 Myr thermal lithosphere. No dioritic composition found necessary. In any case, occur deep levels, where supposed be ductile, way very similar what East African Rift System. From we conclude seismogenic thickness ∼35–40 system first order proportional profile rheologically layered dominated mafic ∼10–45 range. An upper mantle core strength, however, prevents it reaching stress failure greater depth.