HVSR of ambient noise in Ston (Croatia): comparison with theoretical spectra and with the damage distribution after the 1996 Ston-Slano earthquake

Abstract

Horizontal-to-vertical spectral ratios (HVSR) of ambient vibrations measured in the ancient town of Ston (Croatia) on 99 locations, are shown to be well matched to the theoretical ones computed for body-waves as well as for the surface waves. This match is poorer for sites on the slopes of nearby hills. The ratios of measured peak horizontal ground acceleration during the damaging earthquake in 1996 (M L = 6.0) and the ones obtained using empirical attenuation laws is approximately equal to the mapped value of the dynamic amplification factor determined on the basis of observed HVSR in the vicinity of the accelerometric station. The HVSR of the accelerogram is very similar to the HVSR of the ambient noise. The damage to the building stock in the old town centre caused by the earthquake series of 1996 is closely related to the estimated soil amplification and its fundamental frequency. More measurements in buildings are needed to arrive at confident conclusions about possible soil-structure resonance.

Estimation of near-surface attenuation in the tectonically complex contact area of the northwestern External Dinarides and the Adriatic foreland

“…The HVSR methodology proposed by Nakamura (1989) has been used in numerous studies to estimate local seismic ground response as expressed by natural or fundamental frequency (f res ) of soils and HVSR spectral peak amplification, particularly in the broader study area, e.g. in Slovenia (Gosar, 2007;Gosar and Martinec, 2009;Gosar et al, 2010), in Italy (Mucciarelli and Gallipoli, 2001;Di Giacomo et al, 2005;Del Monaco et al, 2013;Panzera et al, 2013) and in Croatia (Herak et al, 2010;Herak, 2011;Stanko et al, 2016Stanko et al, , 2017.…”

Constraints on Complex Faulting during the 1996 Ston–Slano (Croatia) Earthquake Inferred from the DInSAR, Seismological, and Geological Observations

“…(Figure 1). Peak horizontal ground acceleration of 0.64 g recorded in Ston [4] is the largest ever observed in Croatia. The earthquake sequence lasted for about a year, with more than 1800 located aftershocks within 50 km from the mainshock's epicentre.…”

“…The macroseismic epicentre is located close to the Podimoć village, about 10.5 km to the NW from the microseismic epicentre where the fault rupture started ( Figure 6). In order to homogenise the dataset and reduce observations to the average soil, in the inversion we have reduced the observed intensity in Ston by half a degree of MSK (from VIII to VII-VIII MSK), since Herak et al [4] have shown that the damage to the building stock in the old town centre was closely related to the estimated soil amplification determined by ambient noise measurements. The macroseismic epicentre is located close to the Podimoć village, about 10.5 km to the NW from the microseismic epicentre where the fault rupture started ( Figure 6).…”

Estimation of near-surface attenuation in the tectonically complex contact area of the Northwestern External Dinarides and the Adriatic foreland

“…Croatia (Herak et al, 2010;Herak, 2011;Stanko et al, 2016Stanko et al, , 2017. Vlahović et al, 2005).…”