Estimation of detection capability of the VRAC station in respect to seismic events recorded in the years 2011 to 2021
Vol.29,No.1-2(2022)
Broadband seismic station VRAC (Vranov u Brna), operated by Institute of physics of the Earth (Masaryk University) is involved in various projects focused on monitoring of the seismic events. Above all, its involvement in the global seismic network of the International Monitoring System CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization) is very important. The VRAC station is also one of the permanent broadband stations of the Czech Regional Seismic Network. Thus, the data of the VRAC station is routinely processed in respect to detection of the seismic events situated in various epicentral distances, from local, through regional to teleseismic. This article aims to briefly show a simple estimation of the detection capability of the VRAC station with respect to seismic events from various epicentral distances. Discussed estimation of the detection capability was based on study of the magnitude-frequency relations. For this purpose, the set of seismic events recorded by the VRAC station in the years 2011–2021 was used. This set included 52 246 seismic events, 33 161 being regional events situated up to epicentral distance of 2 000 km from the VRAC station. In the framework of the magnitude-frequency analysis, two parameters were determined for each subset containing events from the particular range of epicentral distances: the most frequent magnitude Ma and magnitude Mm in the minimum of the derived non-log magnitude-frequency function. The value of Mm shows well the point where the roll-off effect occurs on the classical magnitude-frequency graph. The graphs of both observed values (Ma and Mm) show steep increase at regional distances, followed by a flat part of the curve at epicentral distances of 20° to 80°. Low detection capability zones in the distances corresponding to seismic shadows zones connected both with the zone of decreased seismic velocities in the deep parts of the Earth (outer core) and in the asthenosphere are distinctly noticeable. Results of the study allow to estimate the detection threshold of the VRAC station between the magnitude value 4.5 to 4.9 in the case of epicentral distances from 20° to 80°.
seismic monitoring; induced seismic events; natural seismicity; detection capability; station VRAC
Bormann, P., Baumbach, M., Bock, G., Grosser, H., Choy, G. L., Boatwright, J. (2009). Seismic Sources and Source Parameters. – In: Bormann P. (ed.). New Manual of Seismological Observatory Practice (NMSOP), Potsdam: Deutsches GeoForschungsZentrum GFZ, 1–94.
CTBTO Preparatory Commission (1996). Comprehensive Nuclear-Test-Ban Treaty (CTBT) and Text on Establishment of a Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization.
Gutenberg, B., Richter, C. F. (1944). Frequency of earthquakes in California. – Bulletin of the Seismological Society of America, 34, 4, 185–188.
Havíř, J. (2004). Detekce vzdálených zemětřesení na stanici VRAC – využitelnost pro účely Mezinárodní monitorovací sítě CTBTO. – In: Sborník 13. regionální konference „Rozvoj seismologie, inženýrské geofyziky a geotechniky“. Sborník vědeckých prací VŠB–TU Ostrava, řada stavební, 4, 2, 105–113.
Havíř, J. (2018). Seismické jevy registrované stanicí VRAC v roce 2017. – Geologické výzkumy na Moravě a ve Slezsku, 25, 1–2, 39–44.
Havíř, J., Švancara, J., Otruba, J. (2003). Úloha a využití nově certifikované seismologické stanice VRAC v rámci Mezinárodního monitorovacího systému CTBTO. – In: Sborník 12. regionální konference „Nové výsledky seismologických, geofyzikálních a geotechnických průzkumů“. Sborník vědeckých prací VŠB-TU Ostrava, řada stavební, 3, 2, 77–84.
Ishimoto, M., Iida, K. (1939). Observation sur les Séismes enregistrés par le Microseismographe construit dernièrement. – Bulletin of Earthquake Research Institute, University Tokyo, 17, 2, 443–478 (japonsky, francouzské resumé).
Kværna, T., Ringdal, G. (2013). Detection capability of the seismic network of the International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty. – Bulletin of the Seismological Society of America, 103, 2A, 759–772.
Veith, K. F., Clawson, G. E. (1972). Magnitude from short-period P-wave data. – Bulletin of the Seismological Society of America, 62, 2, 435–452.
Zedník, J., Pazdírková, J. (2009). Seismicity in the Czech Republic in 2007. – Studia Geophysica and Geodaetica, 53, 2, 269–274.
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Copyright © 2022 Josef Havíř