The role of viscous deformation mechanisms in controlling fault weakening during the propagation of earthquakes.

Faults become transiently weak during the propagation of earthquakes. Fast, efficient lubrication of the sliding portion of seismic faults promotes slip acceleration, rupture propagation and radiation of potentially hazardous waves. Indeed, laboratory experiments show that fault materials dramatically weaken when sheared at seismic velocities (> 0.1 m s-1). Several thermally-activated mechanisms, triggered by shear heating, have been proposed to explain the coseismic weakening of faults. However, a unifying law describing the thermal weakening observed for different rock types is still lacking. We explored this problematic by performing friction experiments in a rotary shear apparatus on powders of a range of rock-forming minerals (calcite, dolomite, anhydrite, sodium chloride and olivine), at seismic velocities up to v = 1.4 m s–1 and normal stresses uptoσn =25MPa. When the experimental fault is weak, sheared gouges consistently develop a well- defined, porosity-free principal slip zone (PSZ) with finite thickness (a few tens of micrometres). PSZ is composed of fine-grained (< 5 μm) crystalline aggregates, which display textures typical of sub-solidus viscous flow. These are similar to those found in natural ultramylonites of ductile, aseismic shear zones active in the lower crust. Calcite experiments were explored in-detail through the monitoring of acoustic emissions and with further microstructural analysis, which integrated SEM EBSD technique and TEM imaging. We show that, at dynamic conditions, thermally-activated viscous mechanisms (e.g. grainsize sensitive and insensitive creep) compete with brittle processes in controlling fault strength. We also show that local temperatures attained during seismic slip control the strength of simulated faults according to an Arrhenius-type law. Our results demonstrate that coseismic lubrication of faults is operated by viscous processes, which can be described by are general, material-dependent Arrhenius-type constitutive equation. Therefore, our essay offers a unifying approach to the quantification of the dynamic strength of faults and to numerical modelling of earthquakes

The anatomy of houses: Materialities of being at home

This introductory essay proposes a reflection that discusses, reframes, and presents the thematic section hosted in this volume, that investigates houses at the intersection between recent trends in the anthropology of the house, the study of material culture, and the investigation of contemporary socio-cultural transformations. In the first paragraph, we contextualize the growing contemporary interest in houses. In the second, following Carsten, we sustain the idea that houses themselves should be placed at the heart of a research agenda, we present the approach proposed in this thematic section, we clarify what are houses and what distinguishes them in relation to homes and households and how, in the history of anthropology, these “objects” have been investigated. In the third paragraph, reviewing the main approaches to the theme, we delve into the notion of société à maisons elaborated by Lévi-Strauss. The fourth paragraph places the concreteness of houses back at the centre of the analysis, where normative and material forms are mediated, reproduced, and even contested or negotiated. In the last, we present the three articles hosted in this thematic section – and the afterword discussing them – that explore how houses and their materiality modify the world and deal with its transformations.Questo saggio introduttivo propone una riflessione che discute, contestualizza e presenta la sezione tematica ospitata in questo volume, che indaga le case all’intersezione tra le recenti tendenze dell’antropologia della casa, lo studio della cultura materiale e l’indagine delle trasformazioni socio-culturali contemporanee. Nel primo paragrafo, contestualizziamo il crescente interesse contemporaneo per le case. Nel secondo, seguendo Carsten, sosteniamo l’idea che le case stesse debbano essere poste al centro di un’agenda di ricerca, presentiamo l’approccio proposto in questa sezione tematica, chiariamo cosa si intenda con “house” e cosa la distingua dai concetti di “home” e “household” e come, nella storia dell’antropologia, questi “oggetti” siano stati indagati. Nel terzo paragrafo, passando in rassegna i principali approcci al tema, approfondiamo la nozione di société à maisons elaborata da Lévi-Strauss. Il quarto paragrafo rimette al centro dell’analisi la concretezza delle case, dove le forme normative e materiali sono mediate, riprodotte e persino contestate o negoziate. Nell’ultimo, presentiamo i tre articoli etnografici ospitati in questa sezione tematica – e la postfazione che li discute – che esplorano come le case e la loro materialità modificano il mondo e affrontano le sue trasformazioni

Expulsionscapes. Logics of Expulsion and Economies of Eviction in Milan (Italy)

Drawing on ethnographic research carried out between October 2015 and December 2016, in this article I employ an anthropological gaze to show the socially and analytically central role evictions play in the contemporary world as a mechanism for producing social exclusion, inequality and difference. In the first section, I outline some contextual elements to frame the housing issue in Italy, while in the second I bring certain conceptual and methodological tools from both anthropology and other disciplines to bear on interpreting the phenomenon of residential eviction. In the third section, I present several case studies investigated during my fieldwork to illustrate four «logics of expulsion» that pave the way for understanding the richness of each «local place» as part of a globally encompassing phenomenon which, borrowing from Appadurai, I have defined as expulsionscape.A partire da una ricerca etnografica condotta tra ottobre 2015 e dicembre 2016, in questo articolo intendo mostrare – attraverso uno sguardo antropologico – la centralità sociale e analitica degli sfratti nel mondo contemporaneo come meccanismo di produzione di esclusione sociale, di disuguaglianza e di differenza. Nel primo paragrafo fornisco alcuni elementi di contesto utili a inquadrare la questione abitativa in Italia. Nel secondo paragrafo tento di delineare alcuni strumenti concettuali e metodologici di carattere antropologico – ma non solo – per interpretare il fenomeno della perdita forzosa dell’alloggio. Nel terzo paragrafo, attraverso alcuni casi di studio emersi durante la ricerca etnografica, illustro quattro «logiche di espulsione» che dimostrano la possibilità di identificare la ricchezza che caratterizza ogni «località» all’interno di un fenomeno che ha una portata globale e ho definito nel corso del testo come expulsionscape, riprendendo gli stimoli di Appadurai

Heidegger ai margini. Antropologia e trasgressione dello spazio urbano: un caso studio

The&nbsp;Programa Especial de Realojamento&nbsp;(PER) offers the opportunity to the municipalities situated in Lisbon and Porto metropolitan areas of succeeding in eliminating clandestine neighborhoods and providing the reallocation of the residents in social houses. The decree contextualizes the housing problem as «a still open plague in our social fabric».The current process implementation, more than twenty-year far from the original formulation, has produced complex adaptation, resistance and fighting dynamics. Through the analyses of an ethnographic case study, the author problematizes the implementation of this governance program, focusing on the consequent systematic demolition of informal settlements in the Lisbon periphery under the aegis of the urban renewal doctrine.The&nbsp;Programa Especial de Realojamento&nbsp;(PER) offers the opportunity to the municipalities situated in Lisbon and Porto metropolitan areas of succeeding in eliminating clandestine neighborhoods and providing the reallocation of the residents in social houses. The decree contextualizes the housing problem as «a still open plague in our social fabric».The current process implementation, more than twenty-year far from the original formulation, has produced complex adaptation, resistance and fighting dynamics. Through the analyses of an ethnographic case study, the author problematizes the implementation of this governance program, focusing on the consequent systematic demolition of informal settlements in the Lisbon periphery under the aegis of the urban renewal doctrine

Global margins. From the production of marginalization to spaces of hope An interview to Ananya Roy Interview edited by Simone Tulumello and Giacomo Pozzi

Simone met Ananya on the morning of July 13, 2018, during the Congress of AESOP, the Association of European Schools of Planning, where Ananya gave the opening keynote speech, titled “Plans for freedom: Borders, cities and the struggle for justice in the age of Trumpism”. The conversation lasted approximately 40 minutes and was based on, but at moments diverged from, a number of questions jointly prepared by Simone and Giacomo. Starting from the double nature of the margin in Ananya’s work – margin as method and as object of study – the conversation then touched issues of race in the making of the contemporary city, mostly in the USA and the Global South. We also discussed representations of urban margins as places of resistance and creativity; and then questioned the return of the nation state in producing, and enforcing, (racial, gendered, class…) margins. Inspired by the topic of the AESOP congress, “Making space for hope”, we concluded by reflecting on the paths for building alternatives to the status quo, reflecting on activist and engaged research practices. By questioning the frequent romanticizing of the local, Ananya reflected on the need for a global scale in thinking change. The following is a transcription of the conversation, lightly edited for clarity, consistence and style.info:eu-repo/semantics/publishedVersio

The role of fault rock fabric in the dynamics of laboratory faults

Fault stability is inherently linked to the frictional and healing properties of fault rocks and associated fabrics. Their complex interaction controls how the stored elastic energy is dissipated, that is, through creep or seismic motion. In this work, we focus on the relevance of fault fabrics in controlling the reactivation and slip behavior of dolomite-anhydrite analog faults. We designed a set of laboratory experiments where we first develop fault rocks characterized by different grain size reduction and localization at normal stresses of σN = 15, 35, 60, and 100 MPa and second, we reload and reactivate these fault rocks at the frictional stability transition, achieved at σN = 35 MPa by reducing the machine stiffness. If normal stress is lowered this way, reactivation occurs with relatively large stress drops and large peak-slip velocities. Subsequent unstable behavior produces slow stick-slip events with low stress drop and with either asymmetric or Gaussian slip velocity function depending on the inherited fault fabric. If normal stress is raised, deformation is accommodated within angular cataclasites promoting stable slip. The integration of microstructural data (showing brittle reworking of preexisting textures) with mechanical data (documenting restrengthening and dilation upon reactivation) suggests that frictional and chemically assisted healing, which is common in natural faults during the interseismic phase, can be a relevant process in developing large instabilities. We also conclude that fault rock heterogeneity (fault fabric) modulates the slip velocity function and thus the dynamics of repeating stick-slip cycles

Towards a genealogy of critical urban studies

Urban Studie

Sottotraccia. Note per una genealogia degli studi urbani critici

Urban Studie