No abstract

The time-averaged shear-wave velocity in the upper 30 m of a site (V S30 ) is commonly used for ground-motion prediction. When measured velocities are unavailable, V S30 is estimated from proxy-based relationships developed for application on global or local scales. We describe the development of a local relationship for Greece, which begins with compilation of a profile database (PDB) from published sources and engineering reports. The PDB contains 314 sites; 238 have profile depths ≥ 30 m and 59 are within 100 m of accelerographs. We find existing relations for extrapolating a time-averaged velocity for depths less than 30 m to V S30 to overpredict V S30 . We present equations for these extrapolations.We then compile proxies for PDB sites, including terrain type, surface geology, and surface gradients at 30 and 3 arcsec resolution (from radar-derived digital elevation models [DEMs]). When checked against ground survey data, we find ground elevations from 3 arcsec DEMs to be more accurate relative to survey data than alternative 30, 9, and 1 arcsec DEMs. Drawing upon expert opinion, we develop geologic categories based on age, gradation, and depositional environment and assign such categories to PDB sites. We find an existing 30 arcsec gradient-based global model to be biased relative to local V S30 data for gradients >∼0:05 m=m. Bias relative to a California model is also found for four of the eight well-populated geomorphic categories, and new (local) values are provided. We find statistically significant effects of the 3 arcsec gradient on V S30 for Quaternary and Tertiary materials but no gradient effect for those from the Mesozoic. Among Quaternary sediments, Holocene, mapped Quaternary (age unspecified), and mixed/fine-gradation materials exhibit consistent V S30 -gradient trends, whereas Pleistocene and coarse-gradation sediments have faster velocities. For the study region, we recommend use of the modified terrain-and geology-based methods in combination for proxy-based V S30 estimation.

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The central Italy earthquake sequence has, to date, generated three mainshocks:M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016. These events, along with aftershocks, were well recorded by Italian networks, and are among the normal fault earthquakes with the highest number of recordings globally. We process records for six events using NGA/PEER procedures. Many recording sites lacked VS30 assignments, which we provide using measured shear wave velocity profiles where available and a local geology proxy otherwise. Stations at close distance, including near the hanging wall, exhibit fling step in some cases but no obvious rupture directivity. The data exhibit fast anelastic attenuation at large distances (>100 km), as predicted by recent Italy-adjusted global models, but not by Italyspecific models. We partition residuals from Italy-adjusted global models, finding negative event terms at short periods (weaker than average shaking). We apply Kriging of within-event peak acceleration and velocity residuals using a global semi-variogram model to estimate the spatial distribution of peak accelerations, which are generally most intense south-west of Mt. Vettore.

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This paper presents the results of an experimental investigation of the dynamic properties of two expanded polystyrene (EPS) geofoam materials. Torsional resonant column tests and cyclic uniaxial tests were conducted on block-molded EPS geofoam specimens with mean densities of 12.4 and 17.1 kg/m3, under zero confining pressure. The estimated dynamic moduli values (shear modulus and modulus of elasticity) and damping ratio values are presented as functions of cyclic strain amplitude and loading frequency. The geofoam behavior for strains ranging from 5 × 10-4 to 8.0% was studied by combining the results of the two types of tests. It was found that EPS geofoam behaves linearly for strain values of up to 0.1%; however, a strong nonlinearity develops for strains greater than 1%. The geofoam density significantly affected the dynamic moduli values (the moduli increase with increasing density) whereas no appreciable effect on damping ratio values was found. The damping ratio values were very low (∼1%) for strains less than 0.1% and gradually increased to 10% for strains greater than 1%. The test results also indicated that frequency of loading does not significantly affect the moduli values, whereas the damping ratio values decreased with increasing frequency values. Based on the test results, shear modulus, G/G0, versus cyclic shear strain amplitude, ξc, and damping ratio, D versus ξc, curves are proposed to describe the EPS geofoam nonlinear properties.

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The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlights valuable lessons learned regarding faulting and ground motions, engineering effects, and emergency response to this disaster.