Estimating Geophysical Bedrock Depth Using Single Station Analysis and Geophysical Data in the Extra-Carpathian Area of Romania

Ground-motion models for Vrancea intermediate-depth earthquakes

“…The variability of the f 0 in our dataset is between 0.1 and 15 Hz, where the highest one is attributed to the bedrock condition. The f 0 values are inferred from Manea et al (2016Manea et al ( , 2019Manea et al ( , 2020 and Coman et al (2020), where its variability is presented along different tectonic units and areas. The distributions of the within-event residuals with all site parameters (EC8 soil classes and f 0 ) are presented in Figures S2-S10 in the Supplementary Materials (d, e) for PGA, PSA (0.3, 0.7, 1, 3, 5, 7, and 10 s) and PGV and show that no further dependency exists.…”

“…For comparison purposes, a regular grid, with a resolution of 15 km, encompassing all of Romania was used. The fundamental frequency of resonance requested by the new GMM was extracted at each grid node by interpolating the f 0 at all the seismic stations from permanent network and temporary arrays published by Manea et al (2016Manea et al ( , 2019Manea et al ( , 2020 and Coman et al (2020). In addition, the grid describes the amplification zonation of Setal08.…”

“…This parameter is directly linked with the depth of the seismic bedrock used in engineering studies (e.g. Fäh et al, 2003; Manea et al, 2016; Poggi et al, 2012) and was assessed at all the seismic stations of the Romanian Seismic Network, in several studies: Manea et al (2016, 2019, 2020) and Coman et al (2020). In the aforementioned studies, f 0 was extracted by computing the horizontal-to-vertical Fourier spectral ratio based on ambient noise and not earthquakes as the predominant frequency of Vrancea records varies depending on earthquake magnitude and can be different than f 0 at each site (Manea et al, 2017, 2021); The main advantage of using f 0 is that it does not need additional computation as is required for the sediment depth retrieval and in this way does not include large epistemic uncertainties within the ground-motion computation.…”

“…Nakamura, 1989) on ambient vibration and offers essential information about the local structure (e.g. Manea et al, 2020; Poggi et al, 2012). For complex sedimentary structures, the f 0 is a robust proxy for characterizing the local site response as it provides information about the impedance contrast between surface and underlying stiff deposits or rock basement (Fäh et al, 2003), which in turn is one of the main sources of the soil amplification (Pitilakis et al, 2019).…”

“…For complex sedimentary structures, the f 0 is a robust proxy for characterizing the local site response as it provides information about the impedance contrast between surface and underlying stiff deposits or rock basement (Fäh et al, 2003), which in turn is one of the main sources of the soil amplification (Pitilakis et al, 2019). Given the amplification effects of the thick sediments (<10 km) located in front of the Carpathian arc, the f 0 was retrieved at each seismic station from recent investigation in the region (Coman et al, 2020; Manea et al, 2016, 2019, 2020). Correlation between f 0 and the site response was observed by different authors (e.g.…”