The magnetic field of Baikal rift on the data of precision surface survey

Rakhmatulin R.A.1, Khomutov S.Y.2, Kharchenko V.V.1, Lipko Yu.V.1
  1. Institute of Solar-Terrestrial Physics of SB RAS, Irkutsk, RUSSIA
  2. Altay-Sayan Branch of Gephysical survey of SB RAS, Novosibirsk, RUSSIA 1

The results of the precision magnetic survey during 2009-2010 on Lake Baikal ice and in the Northern part
of the Olkhon Island are presented. The main traverse of survey were routed along the Academic ridge from
the Olkhon Island to Bolshoy Ushkany Island and from the western to the eastern lakesides of the Baikal; other
short tracks were routed across the Olkhon Island. The Overhauser proton magnetometer POS-1 was used to
measure field F intensity modulus. Magnetic declination D and inclination I were measured by DI-magnetometer
on the base of a theodolite 3T2KP and a fluxgate device. Spatial variations of the vertical component dZ were
measured by M-27M magnetometer. Spatial resolution along the route is about 5 km for F and dZ and about
10 km for total vector. The accuracy of the measurement is estimated as about 0.5 nT, 1 arcmin and 0.2 arcmin
for F, D and I, correspondingly. Geomagnetic variations during the survey were controlled by the data from
the magnetic observatories "Uzur" ( the Olkhon Island), "Patrony" (Irkutsk), and "Klyuchi" (Novosibirsk).
In the result of field measurements the maps of distribution of magnetic field in the central part of the
Baikal Lake between Olkhon and Bolshoy Ushkany islands were drawn. This maps were compared with the
results of previous surveys. A large-scale magnetic anomaly which had not been presented on magnetic maps
of this region was found in the survey area. The peculiarities of precise magnetic surveys on ice surface are
discussed. This work was supported by the Russian Foundation for Basic Research and the Administration of
Irkutsk region (regional grant 08-05-98073-r-Siberia-a).