The role of static stress diffusion in the spatio-temporal organization of aftershocks

We investigate the spatial distribution of aftershocks and we find that aftershock linear density exhibits a maximum, that depends on the mainshock magnitude, followed by a power law decay. The exponent controlling the asymptotic decay and the fractal dimensionality of epicenters clearly indicate triggering by static stress. The non monotonic behavior of the linear density and its dependence on the mainshock magnitude can be interpreted in terms of diffusion of static stress. This is supported by the power law growth with exponent $H\simeq 0.5$ of the average main-aftershock distance. Implementing static stress diffusion within a stochastic model for aftershock occurrence we are able to reproduce aftershock linear density spatial decay, its dependence on the mainshock magnitude and its evolution in time.Comment: 4 figure

Dynamical scaling in branching models for seismicity

We propose a branching process based on a dynamical scaling hypothesis relating time and mass. In the context of earthquake occurrence, we show that experimental power laws in size and time distribution naturally originate solely from this scaling hypothesis. We present a numerical protocol able to generate a synthetic catalog with an arbitrary large number of events. The numerical data reproduce the hierarchical organization in time and magnitude of experimental inter-event time distribution.Comment: 3 figures to appear on Physical Review Letter

Studio di fattibilità di una variante alla SS1 Aurelia

Nella presente tesi di laurea vengono proposte varie alternative per la realizzazione di una variante Aurelia in provincia della Spezia, sulle quali è stata eseguita una valutazione di sostenibilità ambientale attraverso l'Anlisi Multi Criteri Spaziale

Evaluating the incompleteness magnitude using an unbiased estimate of the bb value

The evaluation of the $b$ value of the Gutenberg-Richter (GR) law, for a sample composed of $n$ earthquakes, presents a systematic positive bias $\delta b$ which is proportional to $1/n$, as already observed by Ogata \& Yamashina (1986). In this study we show how to incorporate in $\delta b$ the bias introduced by deviations from the GR law. More precisely we show that $\delta b$ is proportional to the square of the variability coefficient $CV$, defined as the ratio between {the standard deviation of the magnitude distribution and its mean value.} When the magnitude distribution follows the GR law $CV=1$ and this allows us to introduce a new procedure, based on the dependence of $b$ on $n$, which allows us to {identify} the incompleteness magnitude $m_c$ as the threshold magnitude leading to $CV=1$. The method is tested on synthetic catalogs and it is applied to estimate $m_c$ in Southern California, Japan and New Zealand

Self-sustained oscillator as a model for explosion quakes at Stromboli Volcano

International audienceWe analyze seismic signals produced by explosion-quakes at Stromboli Volcano. We use standard nonlinear procedures to search a low-order effective dynam-ics. The dimension of the reconstructed phase space depends on the number of samples. Namely larger time lengths cor-respond to dynamical systems of different complexity. If we restrict the analysis to the signal associated directly to the source (Chouet et al., 1997), we obtain a phase space dimen-sion equal to two. We reproduce this part of the signal with a simple single self-sustained oscillator

On the influence of time and space correlations on the next earthquake magnitude

A crucial point in the debate on feasibility of earthquake prediction is the dependence of an earthquake magnitude from past seismicity. Indeed, whilst clustering in time and space is widely accepted, much more questionable is the existence of magnitude correlations. The standard approach generally assumes that magnitudes are independent and therefore in principle unpredictable. Here we show the existence of clustering in magnitude: earthquakes occur with higher probability close in time, space and magnitude to previous events. More precisely, the next earthquake tends to have a magnitude similar but smaller than the previous one. A dynamical scaling relation between magnitude, time and space distances reproduces the complex pattern of magnitude, spatial and temporal correlations observed in experimental seismic catalogs.Comment: 4 Figure

Ippolito Marsili. Un giurista medievale alle soglie dell'età moderna

The research presented in this thesis focuses on the Italian iuris doctor Ippolito Marsili (Bologna 1450 - Bologna 1530). One of the founders of criminal law scholarship and teacher of the first known criminal law course, Ippolito Marsili is aknowledged as a prominent scholar of his age; nonetheless, his biographical and scientific profile still awaits an organic recontruction. The aim of the research is to examine a few aspects of the life and work of this jurist, in order to provide a starting point for a possible comprehensive study. The dissertation is divided into two parts. The first part is centered on Marsili's biography. In chapter 1 a short account of the Marsili family is presented; in particular, I highlighted the links of the family with the powerful Milanese Signoria of the Sforza. Chapter 2 is focused on the main stages of the jurist's life. After discussing a few problems concerning his doctoral degree (his alleged canon law degree is missing), I analyzed his professional career as a teacher - in Bologna - and as a judge - mainly in the Sforza dominion. The research shows a very strong, almost frantic connection between these two activities, which sometimes even seem to overlap; such a feature mirrors the bond between theory and practice of law that Marsili will later pour into his works. In his relationship with political power, our character reveals the struggle of the typically medieval, autonomous jurist to exercise his role in the growing, bureaucratic State entities. Finally, the research shows how - contrary to a generally accepted tradition - Marsili cannot be considered the inventor of the \u201csleep deprivation\u201d torture technique, which he arguably gathered from the praxis of the Lugano (Switzerland). The biographical part is completed in chapter 3 with an account of Marsili's literary production: lecturae/commentaria and repetitiones on the Corpus iuris, a few tractatus, a collection of singularia and his consilia. The second part of the thesis examines Marsili's main work, a criminal law treatise named Practica criminalis Averolda nuncupata (approx. 1525). Chapter 4 summarizes the development of criminal law science and the literary genre of Tractatus or Practicae criminales. Marsili's work can be thought of as a transition point between the \u2018medieval forerunners\u2019 and the \u2018mature\u2019 modern Practicae: such a position awards it peculiar and noteworthy features. Chapter 5 is dedicated to the Averolda's formal properties, examined through a comparison with a few other medieval and modern works of the kind. Practicae criminales have a main practical nature: they rationalize the criminal law emerging from medieval courts and statutes outside the scope of the Corpus iuris. Compared to other works, however, Marsili's Practica has a strong theoretical and educational purpose, combined with the practical scopes. Despite being written in the first half of the sixteenth century, the sources employed in this work (as in all the medieval ones) are the roman-canon law and the opinio doctorum. The Courts' decisiones are rapidly overcoming the scholars' law, and will have a central role in the modern Practicae, giving a territorial facet to ius commune; nonetheless, the Averolda completely ignores them, standing by a universalis, scholar-led system. Marsili's use of scholastic dialectics and particularly of the quaestio - resounding medieval procedures - reveals the purpose of extracting general rules and principles from case law, rather than giving precise solutions to each issue; the author intends to guide the reader through the reasoning behind the ermeneutic process. On the contrary, the main modern Practicae tend to reduce the role of the opiniones doctorum - often generically summarized as communis opinio - and to provide definite, clear solutions to practical issues, following the Courts' stylus. Finally, the Practicae criminales are generally deemed to lack a significant contribution to the building of a dogmatic/systematic order specific to penal law. However, the research shows how both the medieval, dialectic patterns and the modern, rationalistic structures of these works do present a \u2018dogmatic development\u2019: through a diachronic analysis of the defensive activity in courtrooms, I highlighted how Marsili and his colleagues, with different methods, shape a set of rules and principles that gradually separate from the system of the Corpus iuris to form a new, modern system of criminal law. In chapter 6 I turned to the contents of the Averolda, examining the first stages of the per inquisitionem procedure. Specific attention is paid to the rules of imprisonment (carceratio), which show a variety of precautionary measures worthy of further, detailed analysis. Overall, the features of Marsili's Averolda mirror the professional outline of the author: both sides of the research clearly reveal a medieval scholar who faces the challenges of the incipient modern world with his own scientific and professional tools: destined to be progressively discarded, yet such tools prove to have been fruitful for the new age, and to provide us with a better understanding of legal history

An Automated Method for Mapping Independent Spatial b Values

We present an automated method for mapping the b values. The algorithm is very simple and presents three advantages: (a) it does not requires any tuning of the parameters like, for instance, a fixed cell size or a maximum radius of the cell; (b) it implies a more appropriate use of the catalog, by using almost all the events in the catalog used (with a tolerance of 1%) with no overlap; (c) it implies the full independence of the b values, thus allowing the statistical comparison of the results using standard tests. Although the resulting b values are comparable with those obtained by applying the other methods of common use in seismology, these latter (a) leave out many earthquakes from the analysis, with loose of useful information, (b) produce diffuse cells overlapping aiming at reaching many cells of the grid in order to get the correct number of events in each cell, and (c) results in correlated b values, which do not allow the test of significance for the differences in the b values. Finally, due to the independence from any ad hoc a-priori choice, our method is suitable for automatic and operator-free procedures.Plain Language Summary The methods usually used in seismology for mapping the b value require the tuning of some parameters depending on the analyzed catalog. Here we propose a method that only implies the choice of the minimum number of earthquakes needed to obtain reliable b value estimates, which does not depend on the specific cases. Due to the mutual complete independence of the resulting b values, the proposed method allows the use of standard statistical tests to compare the results