Attenuation of seismic waves in the Pannonian Basin

In recent years, new seismological, geophysical and geological results have been obtained (Porkoláb et al. 2024, Koroknai et al. 2024, Czecze et al. 2024) and new methods have been developed, necessitating an update to the national seismic hazard map of Hungary. One of the most important steps in this update is to analyze how earthquake-induced ground motion attenuates with source-site distance and magnitude, which can be determined through ground motion prediction equations (GMPEs). Zsíros (1996) found that in the Pannonian Basin, macroseismic intensities attenuated with distance more rapidly than in other regions with comparable low to moderate seismicity — a result that also was corroborated during local magnitude calibration for the area. In the absence of strong motion stations in Hungary, we have to use equations based on records from areas of high seismicity, after proper validation. The selection of GMPEs to perform seismic hazard assessments is challenging for the specific characteristics of the Pannonian Basin, such as shallow crustal earthquakes, thin and warm crust, elevated heat flux, and the lack of a sufficient number of medium and large earthquakes. Due to medium seismicity and the lack of strong motion stations, we can only use weak motion records for the research. Our research focuses on gathering and processing of digital records of medium-magnitude earthquakes in the Pannonian Basin since 1995 and recorded by stations in Hungary, surrounding countries, as well as by temporary stations of international projects. This includes calculating various motion parameters and formulating a distance- and magnitude-dependent attenuation equation that fits this dataset. We select GMPEs developed for high seismicity, active shallow crustal zones. Statistical approaches, including the classical residual, likelihood, and log-likelihood are used to evaluate the performance of the GMPEs. This study's outcomes recommend GMPEs optimized for probabilistic seismic hazard analysis in Hungary, considering the basin's distinct seismic attributes.

References:

Czecze B., Győri E., Timkó M., Kiszel yM., Süle B., & Wéber Z. (2024). A Kárpát-Pannon régió szeizmicitása: aktualizált és átdolgozott földrengés-adatbázis. Földtani Közlöny, 153(4), 279. https://doi.org/10.23928/foldt.kozl.2023.153.4.279

Koroknai B., Békési E., Bondár I., Czecze B., Győri E., Kovács G., Porkoláb K., Tóth T., Wesztergom V., Wéber Z., & Wórum G. (2024). Magyarország szeizmotektonikai térképe. Földtani Közlöny, 153(4), mapD. https://doi.org/10.23928/foldt.kozl.2023.153.4.mapD

Porkoláb, K., Békési, E., Győri, E., Broerse, T., Czecze, B., Kenyeres, A., ... & Wéber, Z. (2024). Present-day stress field, strain rate field and seismicity of the Pannonian region: overview and integrated analysis. Geological Society, London, Special Publications, 554(1), SP554-2023.

Zsíros, T. (1996) Macroseismic focal depth and intensity attenuation in the Carpathian region. Acta Geod. Geoph. Hung. 31, 115-125.