BEST: Baikal Explosion Seismic Transect
Abstract
The Baikal Rift Zone is located in Siberia at the centre of the worlds largest continental area. Hence, it offers a unique oportunity for studying the processes of intracratonic rifting. The BEST project "Baikal Explosion Seismic Transects" includes two deep seismic profiles at the southern end of Lake Baikal. The field project was carried out in October 2003 after a pilot project (BASE) in September 2002. The aim of the project is to determine the crustal and upper mantle seismic velocity structure. The two profiles are: (1) a 350 km long, NS-trending profile across the rift zone from Kyahta at the Mongolian border to Cheremhovo, and (2) a 300 km long EW-trending profile along-strike of the rift zone at the northern shore of the lake into the Tunga depression to Mondy at the Mongolian border. The primary seismic sources were 13 explosions in boreholes, each with a 500 kg to 3 ton charge. Supplementary sources were airgun shots in the lake (one 100 l airgun on profile 1, one 30 l airgun on profile 2) and the supervibrator located at Babushkin near the cross point between the two profiles at the shore of the lake. We present the preliminary results of the BEST project regarding the key scientific questions: (1) Determination of the crustal velocity structure, with primary attention to the graben geometry, (2) determination of the propagation properties of seismic waves in the area, (3) test of crustal thinning across the rift zone, (4) determination of the influence of pre-existing structure for the initiation of the rift, (5) comparison of seismic reflectivity outside and underneath the rift zone, to identify locations of major magmatic intrusions into the lower crust; is there a correlation to volcanic activity at the surface? and (6) determination of the seismic Pn wave velocity to identify weak zones in the uppermost mantle.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....7284T