"Trade and the structure of cities"

Our purpose is to investigate how the interplay between trade, commuting and communication costs shapes the economy at both the interregional and intra-urban levels. Specifically, we study how economic integration affects the internal structure of cities and show how decentralizing the production and consumption of goods in secondary employment centers allows firms located in a large city to maintain their predominance. Several new results in both economic geography and urban economics are established, which all agree with empirical evidence.

Residential equilibrium in a multifractal metropolitan area

A residential location model derived from urban economics is combined with the geometry of a multifractal Sierpinski carpet to represent and model a metropolitan area. This area is made up of a system of built-up patches hierarchically organised around a city centre, and green areas arranged in an inverse hierarchical order (large open-spaces in the periphery). An analytical solution is obtained by using a specific geographic coding system for computing distances. The values of the parameters used in the model are based on the French medium sized metropolitan areas; a realistic benchmark is proposed and comparative-statics simulations are performed. The results show that the French peri-urbanisation process (which took place from 1970 onward) can be explained by an increase in income and a reduction in transport costs. Nevertheless, changes in household preferences, in particular an increased taste for open spaces, can also contribute to urban sprawl by making the gradient of land rents less steep and by making peripheral household locations more desirableperi-urban, residential localisation, fractal geometry, amenities

Space-time patterns of urban sprawl, a 1D cellular automata and microeconomic approach

We present a theoretical model of residential growth that emphasizes the path-dependent nature of urban sprawl patterns. The model is founded on the monocentric urban economic model and uses a cellular automata (CA) approach to introduce endogenous neighbourhood effects. Households are assumed to both like and dislike the density of their neighbourhood, and trade-off this density with housing space consumption and commuting costs. Discontinuous spatial patterns emerge from that trade-off, with the size of suburban clusters varying with time and distance to the centre. We use space-time diagrams inspired from 1D elementary CA to visualize changes in spatial patterns through time and space, and undertake sensitivity analyses to show how the pattern and timing of sprawl are affected by neighbourhood preferences, income level, commuting costs or by imposing a green belt.urban sprawl, open space, neighbourhood externalities, cellular automata, residential dynamics.

Residential Equilibrium in a Multifractal Metropolitan Area.

In this paper, an urban economic model of residential location is combined with multifractal geometry (Sierpinski carpet) in order to model and analyse the spatial structure of a metropolitan area. This area is made of an urban system organised hierarchically around a central CBD, as well as of green spaces that have an inverse hierarchical organisation. The properties of the model are studied by means of analytical solutions. Then, simulation are made, which are based of French urban realities. This enables one to choose realistic parameters and to analyse the effects of several modelling assumptions (changes in preferences, economic shocks, …). The modelling results show that French periurbanisation of the last 30 years can be explained by the increase in income and by the decrease in transportation costs, probably without any changes in households preferences

Poly-phased fluid flow in the giant fossil pockmark of Beauvoisin, SE basin of France

The giant Jurassic-aged pockmark field of Beauvoisin developed in a 800 m wide depression for over 3.4 Ma during the Oxfordian; it formed below about 600 m water depth. It is composed of sub-sites organized in clusters and forming vertically stacked carbonate lenses encased in marls . This fine-scale study is focused on a detailed analysis of petrographical organization and geochemical signatures of crystals that grew up in early to late fractures of carbonate lenses, surrounding nodules, and tubes that fed them. The isotopic signature (C, O and Sr) shows that at least three different episodes of fluid migration participated to the mineralization processes. Most of the carbonates precipitated when biogenic seepage was active in the shallow subsurface during the Oxfordian. The second phase occurred relatively soon after burial during early Cretaceous and thermogenic fluids came probably from underlying Pliensbachian, Late Toarcian or Bajocian levels. The third phase is a bitumen-rich fluid probably related to these levels reaching the oil window during Mio-Pliocene. The fluids migrated through faults induced by the emplacement of Triassic-salt diapir of Propiac during the Late Jurassic and that remained polyphased drain structures over time

La localisation des activités économiques et la consommation de terres agricoles

National audienceAlors que la « consommation » des terres agricoles par l’urbanisation est un sujet sensible, l’évaluation de cette consommation peut varier du simple au double selon les définitions et les nomenclatures que l’on utilise

Le marché foncier agricole sous l'influence de la périurbanisation

National audienc

Regard économique sur la périurbanisation

National audienc

Le marché foncier : une machine à hacher la société

Nous montrons, en particulier, que les dix plus grandes métropoles de province sont les gagnantes de la course aux emplois. Cette concentration est vertueuse : les économistes savent, depuis toujours pourrait-on dire, que les grandes villes sont le moteur de la croissance. Nous verrons également que cette concentration métropolitaine s'étend et s'étale dans l'espace : ce sont les banlieues et les périphéries périurbaines qui en profitent plus que les villes centres, dans les plus grandes métropoles comme dans l'ensemble du système urbain français. L'étalement des emplois est général : les emplois stratégiques de ce que l'Insee appelle les « cadres de fonctions métropolitaines » migrent vers la périphérie des grandes villes, les emplois industriels font de même, et ceux des services aux particuliers aussi. Le mouvement d'étalement se nourrit aussi du flux des ménages quittant les villes vers les espaces périurbains, qui l'emporte sur le flux de sens inverse avec une constance maintenue depuis plus de 30 ans. Cet étalement des métropoles est, lui aussi, vertueux sur le plan économique : il réduit les coûts urbains - coûts fonciers et coûts de transport. Il améliore donc la compétitivité des entreprises. Mais c'est peut être au détriment de l'environnement et de la vie sociale : d'une part, les émissions de gaz à effet de serre et la consommation d'espaces ouverts peuvent s'en trouver accrus, quoique ce ne soit pas un résultat inéluctable ; d'autre part, la ségrégation sociale de l'espace peut également s'accentuer du fait de cet étalement. L'analyse qui est menée dans cet article considère tout d'abord la localisation des entreprises, sur le plan théorique et sur le plan factuel, puis celle des ménages, avec également les deux volets des enseignements de la théorie et des fait

Le choix de la localisation résidentielle des ménages obéit à de bonnes raisons économiques

Cette publication porte également le n° ISBN : 978-2-11-128682-5National audienc