Seredkina Alena I. and Melnikova Valentina I.

ale@crust.irk.ru

7-3952-427570

7-3952-426900

Institute of the Earth's Crust of Siberian Branch of the RAS, 128, Lermontova str., Irkutsk, 664033, Russia

http://www.sbras.ru/sbras/db/dep.phtml?3

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eng

Bukchin B. Determination of source parameters from surface waves recording allowing for uncertainties in the properties of medium // Izv. Akad. Nauk SSSR, Fizika Zemli. 1990. 25. pp. 723–728. Lasserre C., Bukchin B., Bernard P., Tapponier P., Gaudemer Y., Mostinsky A., Dailu R. Source parameters and tectonic origin of the 1996 June 1 Tianzhu (Mw=5.2) and 1995 July 21 Yongen (Mw=5.6) earthquakes near the Haiyuan fault (Gansu, China) // Geophys. J. Int. 2001. Vol. 144. No. 1. pp.?206-220. Seredkina A.I., Melnikova V.I. The seismic moment tensor of earthquakes in the Pribaikalye Region based on surface waves // Doklady Akademii Nauk, Geophysics. 2013. Vol. 451. Part?1. pp. 746–749.

Estimation of source parameters of the Baikal rift zone earthquakes. From 2003, the IEC used the directions of first motions of P-waves to determine the fault plane solutions of large earthquakes in Baykal rift zone. From the data month of February 2011, the IEC uses the inversion of surface wave amplitude spectra to estimate the earthquake source parameters. The procedure is based on the method described by (Bukchin, 1990, Lasserre et al., 2001, Seredkina, Melnikova, 2013). It is assumed that the velocity and density of the propagating medium are given near the source and under each station recording the seismic event and that all of the following hypotheses are valid: an instantaneous pure double-couple point seismic source with known origin time and epicenter location, and a medium with weak lateral inhomogenities. The seismic source is then completely defined by its double-couple depth, its seismic moment and its focal mechanism parameters – whether expressed by the strike, dip and slip angles of the nodal planes or by the two unit vectors in the directions of principal compression and tension axes. The Love and Rayleigh fundamental modes are retrieved from the IRIS, GEOSCOPE and GEOFON broad-band digital records. However if only absolute values of surface wave spectra are used four equivalent solutions are obtained due to the sign ambiguity of moment tensor components and to the symmetry of the radiation patterns of surface wave amplitude spectra with respect to the epicenter. To resolve this ambiguity the solid polarities of P-wave first motions at regional stations were used in the inversion. So a joint inversion of their amplitude spectrum and of P-wave first-motion polarities was performed to calculate the focal mechanism parameters, the depth and the seismic moment of the earthquake under investigation.

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