The large earthquake of 27 August 2008 in Lake Baikal and its precursors

The large earthquake which shook the southern part of Lake Baikal on August 27, 2008 has received much scientific and public interest. The occurrence of the event in the high-seismicity Baikal rift was not surprising but its origin time was, as usual, unexpected. We discuss the geological conditions of the earthquake, its macroseismic effects, and some data interpreted as its precursors. A special focus is made on preseismic changes in dissolved helium in Lake Baikal. Studying helium patterns in a deep freshwater lake in an active seismic area is a pioneering experience that appears to have no match in the world earthquake prediction practice.