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EXAMINING THE CONSISTENCY OF FOCAL PARAMETERS PUBLISHED BY NATIONAL EARTHQUAKE AGENCIES OF TURKEY

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Abstract

Two national agencies are operating in Turkey providing routine analysis of earthquakes of Turkey and surroundings, Bo?azi?i University - Kandilli Observatory and Earthquake Research Institution (BOUN?KOERI) and Disaster and Emergency Management Authority, Earthquake Department (AFAD?DDA). In the present work, we check the consistency of the focal parameters provided by these centers for a large number of recently occurred earthquakes. To perform this test, we used the solutions provided by International Seismological Centre (ISC) as reference ones against which the focal parameters provided by the two agencies under test are compared. The data set includes focal parameters of 46,738 earthquakes, covering the period 2000-March 2015, for which reviewed locations are provided by ISC and, at the same time, all necessary parameters from KOERI and DDA are available. The region covered by the data is bounded by the coordinates 35В°-42В°N and 26В°-45В°E extending over the whole area of Turkey and surroundings. The differences in the estimations of origin time, epicenter coordinates, focal depths and magnitudes, provided by KOERI and DDA and the respective estimations of ISC as well as their variation in space and with time are examined. Comparisons have been performed by using all available data as well as after keeping earthquakes with satisfactory azimuthal coverage of stations (GAP?180В°). The GAP (maximum angle between azimuths of the sites of two successive stations to the epicenter) is smaller for ISC, as it is expected since this agency is a collective one using stations of many regional networks all over the globe. Regarding the two examined centers, KOERI seems to prevail for GAP<180В°. KOERI?s estimations of origin time are more compatible to ISC?s ones than those of DDA. The differences in epicenter estimations by KOERI and DDA from those of ISC are almost the same for 100В°<GAP<200В°. Beyond these values, DDA exhibits clearly less consistency to ISC?s locations than that of KOERI. Remarkable deviations are observed in focal depth estimations provided by both examined agencies, showing that further work is necessary towards this direction. We believe that an important step forward must be taken by relocating all the recent regional events using all available phase data and considering a 3-d crustal model, representative for this region.

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DOI resolver: doi.org/10.5593/sgem2018/1.1/s05.098

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