Alessandro Pagliaroli

Geotechnical Aspects of the L’Aquila Earthquake

On April 6, 2009 an earthquake (ML = 5.8 and MW = 6.3) stroke the city of L’Aquila with MCS Intensity I = IX and the surrounding villages with I as high as XI. The earthquake was generated by a normal fault with a maximum vertical dislocation of 25 cm and hypocentral depth of about 8.8 km. The deaths were about 300, the injured were about 1,500 and the damage was estimated as high as about 25 billion €. Both maximum horizontal and vertical components of the accelerations recorded in the epicentral area were close to 0.65 g. The paper summarises the activities in the field of earthquake geotechnical engineering aimed to the emergency and reconstruction issues. The ground motion recorded in the epicentral area is analysed; the geotechnical properties measured by in-situ and laboratory tests before and after the earthquake are summarised; site effects are preliminarily evaluated at accelerometric stations locations and damaged villages; the outstanding cases of ground failure are finally shown.

International Benchmark on Numerical Simulations for 1D, Nonlinear Site Response (PRENOLIN): Verification Phase Based on Canonical Cases

PREdiction of NOn‐LINear soil behavior (PRENOLIN) is an international benchmark aiming to test multiple numerical simulation codes that are capable of predicting nonlinear seismic site response with various constitutive models. One of the objectives of this project is the assessment of the uncertainties associated with nonlinear simulation of 1D site effects. A first verification phase (i.e., comparison between numerical codes on simple idealistic cases) will be followed by a validation phase, comparing the predictions of such numerical estimations with actual strong‐motion recordings obtained at well‐known sites. The benchmark presently involves 21 teams and 23 different computational codes. We present here the main results of the verification phase dealing with simple cases. Three different idealized soil profiles were tested over a wide range of shear strains with different input motions and different boundary conditions at the sediment/bedrock interface. A first iteration focusing on the elastic and viscoelastic cases was proved to be useful to ensure a common understanding and to identify numerical issues before pursuing the nonlinear modeling. Besides minor mistakes in the implementation of input parameters and output units, the initial discrepancies between the numerical results can be attributed to (1) different understanding of the expression “input motion” in different communities, and (2) different implementations of material damping and possible numerical energy dissipation. The second round of computations thus allowed a convergence of all teams to the Haskell–Thomson analytical solution in elastic and viscoelastic cases. For nonlinear computations, we investigate the epistemic uncertainties related only to wave propagation modeling using different nonlinear constitutive models. Such epistemic uncertainties are shown to increase with the strain level and to reach values around 0.2 (log_(10) scale) for a peak ground acceleration of 5  m/s^2 at the base of the soil column, which may be reduced by almost 50% when the various constitutive models used the same shear strength and damping implementation.

Numerical Evaluation of Topographic Effects at the Nicastro Ridge in Southern Italy

Numerical site response analyses were carried out on the Nicastro ridge in Southern Italy in order to investigate topographic effects. First, the analyses were carried out on a simplified model by employing simple artificial signals, in order to get preliminary physical insights into the two-dimensional phenomena involved. Then, numerical analyses were carried out on a more realistic heterogeneous subsoil model developed on the basis of geotechnical and geophysical investigations. Real accelerograms were selected for these analyses. Particular attention was devoted to separating topographic from stratigraphic amplification. Finally, the topographic amplification factors were compared with literature data and Eurocode 8 recommendations.

Dynamic characterization of soils and soft rocks of the Central Archeological Area of Rome

The paper presents the results of in-situ and laboratory tests aimed at defining the cyclic properties of soils and soft rocks of the Central Archeological Area of Rome in the framework of the seismic microzonation study of the area. The small-strain shear modulus

PRENOLIN: International Benchmark on 1D Nonlinear Site‐Response Analysis—Validation Phase Exercise

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Seismic microzonation of the central archaeological area of Rome: results and uncertainties

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Seismic microzonation of level 1 of the historic center of Rome

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