Materials of the International Conference
50th Anniversary of the International Geophysical Year
and Electronic Geophysical Year

16-19 September 2007 • Suzdal, Russia

Application of dynamic calibration's method of IMS stations from the Central Asian region

O. K. Kedrov2, E. O. Kedrov1, N. A. Sergeeva1, L. P. Zabarinskaya1, and G. A. Sobolev2

1Geophysical Center Russian Academy of Sciences, Moscow, Russia

2Institute of Physics of the Earth Russian Academy of Sciences, Moscow, Russia

Abstract

Method of Dynamic Calibration (MDC) of seismic stations, based on natural seismicity data was applied for calibration of the International Monitoring System (IMS) stations for the Central Asian region. The algorithm of the method was refined and the software for calibration of diagnostic parameters (DP), characterizing a seismic source for the examined source-station traces, was created. Calibration of stations in the explored region (ER) by MDC is executed by selection of attenuation constants for DP, adapting them for the conditions of the basic region (BR). This method takes the stable region of Eurasia as a base region, including Nuclear Test Sites in Kazakhstan and China. Digital data samples of earthquakes from the International Data Center (IDC) archive for five IMS stations – MKAR, BVAR, EIL, ASF and CMAR for the region of Central Asia were applied for calibration. The present work utilizes DP in a spectral and time domain of DX = Xi - am mb - bΔ lg Δ mode, independent of magnitude and epicentral distance, which were worked out in frame of the method of events identification on regional distances in Eurasia. MDC assumes that calibration factor am doesn't depend on the region, and factor bΔ depends only on geologic-tectonic medium properties irrespective of a source type. Consequently, it is acceptable to assess factor bΔ only by earthquakes sampling in ER and to adapt parameters D(Xi) in ER to BR. Algorithm is designed in such a way, that estimated values of calibration factors bΔ are using for calculation of the corrected DX values and then for screening of natural events in the ER. Experimental estimations of screening efficiency depending on a station vary within the range of 95–100%. The independent MDC testing was performed using the records of explosions in India on 11 May 1998 and in Pakistan on 28 May 1998 received at BRVK and MAKZ stations of IRIS network, analogous by their location and recording equipment characteristics to IMS stations BVAR and MKAR. This testing provided correct results of identification of the source type and have directly confirmed the relevance of the proposed method of calibration of stations according to natural seismicity data. It's showed that calibration factors bΔ for source-station traces, similar by the conditions of signals propagation (as for traces from Iran to the stations EIL and ASF), prove to be comparable practically for all diagnostic parameters. The conclusion is being drawn that the method of dynamic calibration of stations based on natural seismicity data in the region, where the explosions didn't take place, could prove to be significant for rapid and low-cost calibration of IMS stations. MDC can also be applied, for example, for identification of industrial chemical explosions, which wrong classified in regional catalogues as natural earthquakes.

Citation: O. K. Kedrov, E. O. Kedrov, N. A. Sergeeva, L. P. Zabarinskaya, and G. A. Sobolev (2007), Application of dynamic calibration's method of IMS stations from the Central Asian region, in: Materials of the International Conference '50th Anniversary of the International Geophysical Year and Electronic Geophysical Year', GC RAS, Moscow, doi:10.2205/2007-IGY50conf.

© 2007 Geophysical Center RAS and authors


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