Site response studies and seismic microzoning in the Middle Aterno valley (L’aquila, Central Italy)

Abstract

Following the April 6th, 2009 Abruzzo mainshock, the Italian Civil Protection Department promoted a multidisciplinary study aimed at developing seismic microzonation maps for post-earthquake reconstruction planning. In the framework of this project, a Working Group, including the authors, was assembled to carry out a microzonation study on six villages located in the Middle Aterno valley. This paper focuses on the villages of Castelnuovo and Poggio Picenze, which experienced MCS intensity values of IX-X and VIII-IX, respectively. 1D and 2D linear equivalent site response analyses were carried out on representative geological cross-sections through the damaged centres and the expansion zones. The subsoil models resulting from geological, geotechnical and geophysical investigations were calibrated by comparing numerical amplification functions, in the linear range, with horizontal-to-vertical spectral ratio derived from both aftershocks and noise recordings. The input motions adopted for the analyses were five artificial accelerograms compatible with three response spectra obtained from the Italian seismic code, as well as from ad hoc probabilistic and deterministic studies. The results were expressed in the form of horizontal profiles of amplification factors in terms of peak ground acceleration, F PGA , as well as of the Housner intensity, FH, in two different range of periods; this latter parameter was shown to be almost independent of the input motion and allowed to express the dependency of site amplification on the frequency range. The amplification factors computed along the representative geological sections were finally extended with a rational procedure to the surrounding areas to draw Grade-3 microzonation maps.

Assessment of the Seismic Site Amplification in the City of Ivanec (NW Part of Croatia) Using the Microtremor HVSR Method and Equivalent-Linear Site Response Analysis

“…This study is the first stage towards a comprehensive seismic microzonation map of the city of Ivanec based on the estimation of seismic site amplification using microtremor measurements and HVSR analysis combined with 1-D equivalent-linear site response analysis for different peak ground accelerations [29,[74][75][76][77][78]. Site amplification maps at the predominant peak frequency and ground surface indicated two potentially dangerous seismic microzones: one with a high amplification in the central city area due to soft soil characteristics in the alluvial basin of Bednja River, and the other with a small amplification in the transitional zone from the alluvial basin towards the foothills of Mt.…”

“…Accordingly, the local seismic hazard index [78] should be evaluated for a certain intensity of input ground motion at the bedrock level, local site amplifications, liquefaction potential, predominate frequency of the earthquake motion at the surface, local soil effects, and potential landslides for certain parts of the city area. Given that the city has rapidly grown in recent times, and with future plans for expansion, a full and comprehensive seismic microzonation map [74][75][76][77][78] should be developed to include new and updated spatial master planning documents of the city of Ivanec, especially as the area has experienced moderate earthquakes in the past around Mt. Ivanščica.…”

Soil grouting for the seismic protection of existing buildings

“…The integral quantity SI, which has the dimensions of a displacement, is often adopted as a synthetic ground motion parameter that is able to capture the combined effect of amplitude and frequency content on seismic response and structural damage (Bilotta et al, 2011;Lanzo et al, 2011;Puglia et al, 2013;Vona et al, 2009). …”

The 6 October 1762 Middle Aterno Valley (L'Aquila, Central Italy) Earthquake: New Constraints and New Insights

“…The city of L'Aquila suffered much less damage from the 1762 earthquake than from the 1461, 1703, and 2009 earthquakes. The high level of damage undergone by Castelnuovo in 1762 appears to be due to local large amplifications of ground motion (as occurred following the 2009 earthquake, see Tertulliani et al, 2009;Lanzo et al, 2011), showing its proclivity to be extensively damaged. Conversely, the village of Monticchio appears to have been preserved from heavy damage in 1762, just as it was also in 1703 (Morelli, 1962) and in (Galli et al, 2009.…”