Dario Albarello

Short and long term deformation patterns in the Aegean-Anatolian Systems: Insights from space geodetic data (GPS)

Geodetic measurements (GPS) in the eastern Mediterranean suggest higher rates of motion, of about 10 mm/yr, in the Aegean - Western Anatolian zone with respect to those in the central-eastern Anatolia. In this work we explore the plausibility of the hypothesis that the observed kinematics may be significantly influenced by post - seismic relaxation processes induced by the seismic activation of the North Anatolian Fault since 1939. The major implications of this hypothesis are tentatively quantified by a simplified model, constituted by an elastic lithosphere (100 km thick) coupled with a viscous asthenosphere (250 km thick with a viscosity of 10 19 Pas). The predicted perturbation of the displacement and stress fields is consistent with geodetic velocities and could also account for the major features of seismic activity in the period considered.

Evidence of interrelation between the seismicity of the Southern Apennines and Southern Dinarides

Abstract During the last two centuries the strongest earthquakes in the Southern Apennines (M > 5.5) have almost regularly occurred within a short time (a few months to some years) of the occurrence of earthquakes in Southern Yugoslavia. The high statistical significance of this correspondence suggests the presence of a tectonic connection between the two zones.

Stress diffusion across laterally heterogeneous plates

Stress diffusion following a major dislocation event may provide significant contributions to the stress field present in the neighbouring regions. Seismic regularities observed in the southern Adriatic region are used in the present paper to constrain possible physical models of stress diffusion. Lateral variations in the rheological structure of the lithosphere-asthenosphere system are considered. A diffusion equation with variable diffusivity is obtained using the Elsasser approximation, which describes migration of the stress field after a dislocation event. Approximate solutions of this equation are worked out in the long wavelength limit, showing that diffusion is faster where the lithosphere is thicker and slower where it is thinner. Lithosphere thinning accordingly provides a higher amplitude and longer duration diffusional stress following a dislocation event. This behaviour is particularly evident in a transient regime.

The use of historical data in earthquake prediction : an example from water-level variations and seismicity

Abstract By the end of the last century, seismology in Italy had experienced a period of great fortune and development. In that period, repeated campaigns were undertaken to study the possible relationship between earthquakes and variables such as moon phase, atmospheric pressure and underground water level. Using data from a sample well for the period 1/12/1873–1/12/1874, we performed a nonparametric statistical analysis looking for “spikes” significantly different from random variations in water level. These spikes showed a significant correlation with seismic activity in the neighbourhood of the well. However, because of the small sample size, it was not possible to establish the reliability of this precursor fully. An extension of the data set should provide a more reliable result.

Earthquake forecasting in southern italy on the basis of logistic models

Abstract The interrelation between the seismic activity of the Southern Apennines and Southern Dinarides (Mantovani et al., 1987) seems to be characterized by a proportionality between the magnitude of the Dinaric precursors and the probability of occurrence of a shock of M ⩾ 5.0 in the Apennines. Logistic models are used to define in a quantitative way this relationship and to estimate its statistical significance. The good agreement between the observed data and the obtained relationship is an indication of the reliability of this model for earthquake forecasting purposes.

Comment on “Seismic Hazard Assessment (2003–2009) for the Italian Building Code” by Massimiliano Stucchi, Carlo Meletti, Valentina Montaldo, Helen Crowley, Gian Michele Calvi, and Enzo Boschi

A new reference probabilistic seismic hazard map of Italy was recently presented by Stucchi etxa0al. (2011). The map represents the most recent development of the “Cornell‐McGuire” approach adopted in Italy in the last 20xa0years for hazard assessment and implements current models for epistemic uncertainty treatment. This comment does not address the possible limitations of the considered approach itself, but some important (and possibly misleading) consequences of the representation chosen for hazard outcomes, selection of alternative procedures to be included in the logic‐tree considered to manage the epistemic uncertainty, and some statements about the possibility of using recent seismicity to validate these outcomes. This last point is of major importance since any future development of hazard mapping in Italy strongly depends on a careful evaluation of possible drawbacks inherent in the present formulations that should be pointed out by comparing theoretical outcomes and observations.nnThe first aspect is related to one main result provided in the new hazard map that made it possible to base the design spectra for a building on point hazard data instead of on four intervals of peak ground acceleration (PGA), as was the case for the previous code. The authors claim the advantage of the new map is that it provides unprecedented detail of reference ground motion values associated with a fixed return time. In particular, officially released values (INGV, 2008) provide a PGA with four significant digits at more than 16,000 points. This appears overwhelming when compared to the mere four values associated with the zones of the previous map, with PGA set at 0, 0.15, 0.25, and 0.35 g . However, a closer look at the starting data may cast some doubts …

Evidence of interconnection between seismic activity in the Iberian Peninsula and North African belts

Abstract The seismicity patterns of the North African deformation belts and Iberian Peninsula show a close time correspondence. The high statistical significance of this interrelation, estimated using different techniques, suggests the presence of a tectonic connection between these regions.