baldassarri baronchelli barrat caglioti castellano cattuto complexity dattoli evolutionary_dynamics granular_media granular_media herrmann information_theory kreyon language_dynamics loreto mari mukherjee petri pietronero puglisi quantum_optics roux self_organization servedio statistical_physics techno_social_systems tria zapperi zippers

## 1997 |

Hallgass, Riccardo; Loreto, Vittorio; Mazzella, Orfeo; Paladin, Giovanni Earthquakes statistics and fractal faults Journal Article PHYSICAL REVIEW E, 56 , pp. 1346–1356, 1997. Abstract | Links | BibTeX | Tags: earthquakes, hallgass, loreto, mazzella, paladin, self_organization, statistical_physics @article{b, title = {Earthquakes statistics and fractal faults}, author = {Riccardo Hallgass and Vittorio Loreto and Orfeo Mazzella and Giovanni Paladin}, url = {http://pre.aps.org/abstract/PRE/v56/i2/p1346_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1997XR16000015&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1997}, date = {1997-01-01}, journal = {PHYSICAL REVIEW E}, volume = {56}, pages = {1346--1356}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {We introduce a Self-affine Asperity Model (SAM) for the seismicity that mimics the fault friction by means of two fractional Brownian profiles (fBm) that slide one over the other. An earthquake occurs when there is an overlap of the two profiles representing the two fault faces and its energy is assumed proportional to the overlap surface. The SAM exhibits the Gutenberg-Richter law with an exponent $beta$ related to the roughness index of the profiles. Apart from being analytically treatable, the model exhibits a non-trivial clustering in the spatio-temporal distribution of epicenters that strongly resembles the experimentally observed one. A generalized and more realistic version of the model exhibits the Omori scaling for the distribution of the aftershocks. The SAM lies in a different perspective with respect to usual models for seismicity. In this case, in fact, the critical behaviour is not Self-Organized but stems from the fractal geometry of the faults, which, on its turn, is supposed to arise as a consequence of geological processes on very long time scales with respect to the seismic dynamics. The explicit introduction of the fault geometry, as an active element of this complex phenomenology, represents the real novelty of our approach.}, keywords = {earthquakes, hallgass, loreto, mazzella, paladin, self_organization, statistical_physics}, pubstate = {published}, tppubtype = {article} } We introduce a Self-affine Asperity Model (SAM) for the seismicity that mimics the fault friction by means of two fractional Brownian profiles (fBm) that slide one over the other. An earthquake occurs when there is an overlap of the two profiles representing the two fault faces and its energy is assumed proportional to the overlap surface. The SAM exhibits the Gutenberg-Richter law with an exponent $beta$ related to the roughness index of the profiles. Apart from being analytically treatable, the model exhibits a non-trivial clustering in the spatio-temporal distribution of epicenters that strongly resembles the experimentally observed one. A generalized and more realistic version of the model exhibits the Omori scaling for the distribution of the aftershocks. The SAM lies in a different perspective with respect to usual models for seismicity. In this case, in fact, the critical behaviour is not Self-Organized but stems from the fractal geometry of the faults, which, on its turn, is supposed to arise as a consequence of geological processes on very long time scales with respect to the seismic dynamics. The explicit introduction of the fault geometry, as an active element of this complex phenomenology, represents the real novelty of our approach. |

## 1996 |

Hur, Asa Ben; Hallgass, Riccardo; Loreto, Vittorio A renormalization procedure for directed sandpile models Journal Article PHYSICAL REVIEW E, 54 , pp. 1426–1432, 1996. Abstract | Links | BibTeX | Tags: ben-hur, DDRG, hallgass, loreto, self_organization, statistical_physics @article{b, title = {A renormalization procedure for directed sandpile models}, author = {Asa Ben Hur and Riccardo Hallgass and Vittorio Loreto}, url = {http://pre.aps.org/abstract/PRE/v54/i2/p1426_1, http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=A1996VD67400057&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=0c7ff228ccbaaa74236f48834a34396a}, year = {1996}, date = {1996-01-01}, journal = {PHYSICAL REVIEW E}, volume = {54}, pages = {1426--1432}, publisher = {AMERICAN PHYSICAL SOC}, abstract = {Directed models of self-organized criticality are studied in the framework of a real-space renormalization group of a different type. The identification of a suitable phase space in which to define the renormalization transformation and the coupling with the stationarity condition enables us to clarify the nature of the critical state. The renormalization equations are found to have an attractive fixed point, as expected from the self-critical nature of the model. The values of the critical exponents obtained by this procedure are in excellent agreement with exact results.}, keywords = {ben-hur, DDRG, hallgass, loreto, self_organization, statistical_physics}, pubstate = {published}, tppubtype = {article} } Directed models of self-organized criticality are studied in the framework of a real-space renormalization group of a different type. The identification of a suitable phase space in which to define the renormalization transformation and the coupling with the stationarity condition enables us to clarify the nature of the critical state. The renormalization equations are found to have an attractive fixed point, as expected from the self-critical nature of the model. The values of the critical exponents obtained by this procedure are in excellent agreement with exact results. |

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