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Geoinformatika 2016; 4(60) : 20-28 (in Ukrainian)

THE METHOD OF DETERMINING THE PARAMETERS OF THE SOURCE (POINT AND DISTRIBUTED) USING DATA FROM A LIMITED NUMBER OF SEISMIC STATIONS

D. Malytskyy, O. Hrytsai, A. Pavlova, O. Muyla, O. Astashkina, O. Obidina

Carpathian Branch of the Institute of Geophysics, NAS of Ukraine, 3b, Naukova Str., Lviv, 79060, Ukraine, e-mail: dmytro@cb-igph.lviv.ua, grycaj.oksana@gmail.com,  susyinet@gmail.com, orest-aro@rambler.ru, sac1@ukr.net, obidinaeriol@gmail.com

Purpose. The paper is devoted to mathematical modelling of wave fields in layered half-space generated by point and distributed earthquake using Thomson-Haskell matrix method. We propose a methodology of determining focal mechanisms using a graphical method, and the method for determining the focal mechanism using the data from a limited number of stations; and for construct the fault plane in the case of distributed sources.
Design/methodology/approach. The matrix method is used for modelling seismic waves in a heterogeneous medium, which is represented as a horizontal layered elastic structure. A distributed source is considered here as a sum of point sources, that is each point on the plane in a gap is a seismic wave generator. The obtained results for the displacement fields on the free surface on the layered half-space are used to  determine the seismic moment tensor as a function of time by providing only direct P- and S-waves. We present here the way of determining the slip for distributed sources using the methodology for a point source. Thus, to determining the components of the moment tensor, we use the source time function and a slip numerical method, based on the direct problem solution for inversion signals. We also apply the method for determining the focal mechanism using the data from a limited number of stations, as well as for a single common solution method of transferring the plane gap with a particular station in the hypocentre using a rotation coordinate system.
Findings. We present the results of solving the problem SIV inv 2a. the focal mechanism has been defined by the graphical method and by the method of determining the mechanism of the fire, according to the limited number of stations. The authors have obtained a plane gap using the records from the stations I8, I30 and I34.
Practical implications/value. It could be concluded that characterization of distributed sources, such as bias in rupture, rise time, and the time gap is an important seismic problem.

Keywords: tensor seismic moment, focal mechanism, the plane gap, gap plane orientation angles.

 

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