Seismic Site Classification from the Horizontal-to-Vertical Response Spectral Ratios: Use of the Spanish Strong-Motion Database

Abstract

Normally, the average of the horizontal-to-vertical (H/V) ratios of the 5% damped response spectra of ground motions is used to classify the site of strong-motion stations. In these cases, only the three-orthogonal as-recorded acceleration components are used in the analysis, and all the vector compositions that can generate a different response for each period oscillator are excluded. In this study, the Spanish strong-motion database was used to classify the sites of accelerometric stations based on the predominant periods through the average horizontal-to-vertical spectral ratios (HVSR) of recorded ground motions. Moreover, the directionality effects using the vector composition of the horizontal components of ground motions were also considered in the estimations of H/V ratios. This consideration is a relevant novelty compared to the traditional H/V ratios methods. Only earthquakes with magnitudes above 3.5 and hypocentral distances below 200 km were selected, which resulted in 692 ground-motion records, corresponding to 86 stations, from events in the period between 1993 and 2017. After the analysis, a predominant-period site classification was assigned to each station. On the whole, the obtained mean and standard deviation values of the spectral ratios are comparable to those shown by other researchers. Therefore, the advantages of the proposed procedure, which takes the directionality effects into account, can be summarized as follows: (a) The obtained information is richer and gives enables more sophisticated and realistic analyses on the basis of percentiles and (b) it is easier to detect anomalous stations, sites, and/or accelerograms. Moreover, the method eliminates the effect of directionality as a contributor to epistemic uncertainty.

An Early-Warning System to Validate the Soil Profile during TBM Tunnelling

“…The HVSR method assumes that the ratio of the horizontal (H) and vertical (V) Fourier spectra of surface microtremors is an approximate transfer function for the horizontal motion of surface layers. The validity of this assumption was proved by Nakamura [38][39][40][41] and many other researchers [39,[77][78][79][80][81][82].…”

“…The innovative application is based on developing an easy-to-use and economic procedure, which aims to confirm, or otherwise, the soil profile established in the design phase of the tunnel by comparing the soil natural frequencies ( f n = V s /4H) obtained from soil profile established in the design phase with the soil natural frequencies obtained using the HVSR approach on the microtremors induced by the TBM. The HVSR method has been widely used to establish the soil profile in the design phase of structures and infrastructures [39][40][41][42][43]. On the contrary, in this paper, the HVSR method has been used for the first time concerning the microtremors produced by the TBM to develop an easy-to-use, economical procedure for advanced prediction of the soil profile for an area about 20 m ahead of the TBM digging front.…”

The horizontal-to-vertical spectral ratio and its applications

“…To further solve the directionality [7], Pinzon et al considered the directionality impact on the vector combinations using the horizontal components of the ground motions, according to the predominant period through the average HVSR to classify the site of strong-motion stations. Combining local soil properties [8], Swathi and Neelima, depending on the type of the soil, predominate period, and H/V amplitude from microtremor recordings, classified the Vishakhapatnam city into three major zones [9]. Manisha (2020) used the HVSR estimation to classify sites based on the classical method utilizing predominate frequency, in order to assess the earthquake hazard and mitigate risks [undefined].…”

Intensidad de Arias y duración significativa en análisis dinámico de estructuras

“…La I A es definida mediante la siguiente ecuación, (1) donde a(t) 2 es la aceleración del movimiento del terreno elevada al cuadrado, g es la aceleración de la gravedad y t es la duración total del registro. Estos parámetros están relacionados con la energía del movimiento del terreno registrado que, a su vez, está relacionado con la magnitud y la distancia a la fuente, y las condiciones del sitio [5], [6].…”