Evaluation of Linear and Nonlinear Site Effects for the MW 6.3, 2009 L’Aquila Earthquake

An effective strategy for the seismic risk mitigation needs the use of advanced seismological methodologies for a realistic estimate of the seismic hazard and, consequently, to reduce earthquake damage through a preventive evaluation of vulnerability and actions for structure safety. Prediction of earthquakes and their related effects (expressed in terms of ground shaking) can be performed either by a probabilistic approach or by using modelling tools based, on one hand, on the theoretical knowledge of the physics of the seismic source and of wave propagation and, on the other hand, on the rich database of geological, tectonic, historical information already available. Strong earthquakes are very rare phenomena and it is therefore statistically very difficult to assemble a representative database of recorded strong motion signals that could be analyzed to define ground motion parameters suitable for seismic hazard estimations. That is, the probabilistic estimation of the seismic hazard is a very gross approximation, and often a severe underestimation, of reality. A realistic and reliable estimate of the expected ground motion can be performed by using the Neo-Deterministic Seismic Hazard Analysis (NDSHA), an innovative modelling technique that takes into account source, propagation and local site effects (for a recent review see Panza et al., 2011). This is done using basic principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view

Crustal and upper mantle structure beneath the apennines region as inferred from the study of Rayleigh waves

Rayleigh wave phase velocities were obtained in the period range 12.5–83.3 s using the almost linear array of long period seismic stations installed at Bari (BAI), Grosseto (GSO), Bologna (BOL), and Torino (TNO). The Hedgehog inversion gives a crustal thickness in the range 25–37 km. The presence of a low-velocity layer in the crust is allowed, while low velocity material within a few kilometers of the Moho is required. The shear-wave velocities below 60 km are rather higher than usual channel values. If crustal thicknesses of the order of 37 km are rejected as suggested by other geophysical data then the low-velocity layer in the crust is required in order to satisfy the observed dispersion relation.           ARK: https://n2t.net/ark:/88439/y089438 Permalink: https://geophysicsjournal.com/article/114 &nbsp

Neo-deterministic seismic hazard scenarios for India—a preventive tool for disaster mitigation.

Current computational resources and physical knowledge of the seismic wave generation and propagation processes allow for reliable numerical and analytical models of waveform generation and propagation. From the simulation of ground motion, it is easy to extract the desired earthquake hazard parameters. Accordingly, a scenario-based approach to seismic hazard assessment has been developed, namely the neo-deterministic seismic hazard assessment (NDSHA), which allows for a wide range of possible seismic sources to be used in the definition of reliable scenarios by means of realistic waveforms modelling. Such reliable and comprehensive characterization of expected earthquake ground motion is essential to improve building codes, particularly for the protection of critical infrastructures and for land use planning. Parvez et al. (Geophys J Int 155:489–508, 2003) published the first ever neo-deterministic seismic hazard map of India by computing synthetic seismograms with input data set consisting of structural models, seismogenic zones, focal mechanisms and earthquake catalogues. As described in Panza et al. (Adv Geophys 53:93–165, 2012), the NDSHA methodology evolved with respect to the original formulation used by Parvez et al. (Geophys J Int 155:489–508, 2003): the computer codes were improved to better fit the need of producing realistic ground shaking maps and ground shaking scenarios, at different scale levels, exploiting the most significant pertinent progresses in data acquisition and modelling. Accordingly, the present study supplies a revised NDSHA map for India. The seismic hazard, expressed in terms of maximum displacement (Dmax), maximum velocity (Vmax) and design ground acceleration (DGA), has been extracted from the synthetic signals and mapped on a regular grid over the studied territory

Synthetic seismograms - the Rayleigh waves modal summation

From the latest developments of algorithms for the computation of eigenvalues and eigenfunctions of Rayleigh waves for flat layered anelastic models of the Earth, it is possible to construct, with highly satisfactory efficiency and accuracy, "complete" synthetic seismograms also at high frequencies. Examples are given both for continental and oceanic structural models made up of 70 layers and more and extending to depths of about 1,100 km.         ARK: https://n2t.net/ark:/88439/y047312 Permalink: https://geophysicsjournal.com/article/67 &nbsp

Some applications of seismogram synthesis through the summation of modes of Rayleigh waves

Complete synthetic seismograms can be computed by the superposition of the fundamental and higher modes of Rayleigh waves. The usefulness of this approach is illustrated by the fact that it is possible to reproduce with sufficient detail experimental signals lasting several tens of seconds and having a high-frequency content (up to 1 Hz). The method has been proven to work even for higher frequencies, up to 10 Hz. To illustrate the source and structure modelling using this method, the whole experimental records from the Carder displacement meter at the station El Centro for the 1968 Borrego Mountain earthquake have been fitted. Seismic profiles (displacement, velocity and acceleration) have been synthesized and they clearly show the expected agreement between ray travel times and arrival times of different phases.           ARK: https://n2t.net/ark:/88439/y068630 Permalink: https://geophysicsjournal.com/article/246 &nbsp

Previsione dei terremoti e scenari deterministici di moto del suolo

Previsione dei terremoti e scenari deterministici di moto del suol

Rivalutazione del terremoto del 1117 mediante simulazioni del moto del suolo vincolate dai dati storici

Convegno sulla "Sismicit\ue0 storica dell\u2019Italia del Nord-Est \u2013 Il terremoto di Verona del 1117 e la sismicit\ue0 dell\u2019Italia Nord-orientale\u201d (Verona, 11-13 settembre 2008