SUMMARY
Some geological configurations, like sedimentary basins, are prone to site effects. Basins are often composed of different geological layers whose properties are generally considered as ...spatially homogeneous or smoothly varying. In this study, we address the influence of small-scale velocity fluctuations on seismic response. For this purpose, we use the spectral element method to model the 2-D SH wave propagation on a basin of 1.1 km long and ≈ 60 m deep, representing a 2-D profile in the city of Nice, France. The velocity fluctuations are modelled statistically as a random process characterized by a Von Karman autocorrelation function and are superimposed to the deterministic model. We assess the influence of the amplitude and correlation length of the random velocities on the surface ground motion. We vary the autocorrelation function’s parameters and compute seismic wavefields in 10 random realizations of the stochastic models. The analyses of our results focus on the envelope and phase differences between the waveforms computed in the random and deterministic models; on the variability of ground motion intensity measures, such as the peak ground velocity, the pseudo-spectral acceleration response; and the 2-D basin response (transfer function). We find that the amplitude of fluctuations has a greater effect on the ground motion variability than the correlation length. Depending on the random medium realization, the ground motion in one stochastic model can be locally amplified or deamplified with respect to the reference model due to the presence of high or low velocity contrasts, respectively. When computing the mean amplification of different random realizations, the results may be smaller than those of the reference media due to the smoothing effect of the average. This study highlights the importance of knowing the site properties at different scales, particularly at small scales, for proper seismic hazard assessment.
Quantifying the velocity, volume, and rheology of deep, slow‐moving landslides is essential for hazard prediction and understanding landscape evolution, but existing field‐based methods are difficult ...or impossible to implement at remote sites. Here we present a novel and widely applicable method for constraining landslide 3‐D deformation and thickness by inverting surface change data from repeat stereo imagery. Our analysis of La Clapière, an ~1 km2 bedrock landslide, reveals a concave‐up failure surface with considerable roughness over length scales of tens of meters. Calibrating the thickness model with independent, local thickness measurements, we find a maximum thickness of 163 m and a rheology consistent with distributed deformation of the highly fractured landslide material, rather than sliding of an intact, rigid block. The technique is generally applicable to any mass movements that can be monitored by active or historic remote sensing.
Key Points
We invert landslide velocity and elevation change data for the 3D slip surface
La Clapiere landslide has a maximum thickness of 163m and volume of 38million m3
Distributed deformation, rather than block sliding, best fits observations
We compare magnetic properties of 58 variably serpentinized peridotites from three ophiolite complexes (Pindos, Greece; Oman; Chenaillet, France) and the mid‐Atlantic Ridge near the Kane fracture ...zone (MARK). The Pindos and Oman sites show low susceptibility and remanence (K < 0.02 SI; Ms < 0.4 Am2/kg), while the Chenaillet and MARK sites show instead high susceptibility and remanence (K up to 0.15 SI; Ms up to 6 Am2/kg), regardless of serpentinization degree. Petrographic observations confirm that Pindos and Oman samples contain serpentine with very little magnetite, while Chenaillet and MARK samples display abundant magnetite in serpentine mesh cells. Bulk rock analyses show similar amounts of ferric iron at a given serpentinization degree, suggesting that iron is oxidized during the serpentinization reaction in both cases, but that its distribution among phases differs. Microprobe analyses show iron‐rich serpentine minerals (5–7 wt % FeO) in low‐susceptibility samples, while iron‐poor serpentine minerals (2–4 wt % FeO) occur in high susceptibility samples. The contrasted magnetic properties between the two groups of sites thus reflect different iron partitioning during serpentinization, that must be related to distinct conditions at which the serpentinization reaction takes place. We propose that magnetic properties of ophiolitic serpentinites can be used as a proxy to differentiate between high temperature serpentinization (>∼250–300°C) occurring at the axis (i.e., Chenaillet, similar to serpentinites from magmatically poor mid‐ocean ridges), from lower temperature serpentinization (<∼200–250°C), likely occurring off axis and possibly during obduction (i.e., Pindos and Oman). At both settings, serpentinization can result in significant hydrogen release.
Key Points:
Ophiolite serpentinites display contrasted magnetic properties regardless of serpentinization degree
Magnetic properties of serpentinites from ophiolites can be used as a proxy to differentiate their serpentinization setting (on or off axis)
Both on‐axis and off‐axis serpentinization are able to produce significant hydrogen release
France witnessed its last significant territorial acquisitions during the second half of the nineteenth century, when, in 1860, at the end of the Austro-French Piedmontese War, Napoleon III’s Empire ...annexed Savoy and the County of Nice. Up until that date, the heritage of these annexed provinces belonged to another nation, the Kingdom of Sardinia and its reigning dynasty, the House of Savoy. The change in sovereignty brought about what could be called a process of ‘Frenchification’ of the territory’s historic monuments. This article focuses on the built heritage of the County of Nice, describing the main features of this process, covering short-term administrative questions as well as longer-term scientific and political aspects between 1830 and 1930. At this last date, fascist-inspired irredentism began to question the idea that Nice should be considered a part of France. The establishment in Nice of an office of the French historic monuments administration was by no means the beginning of governmental policies to protect the region’s monumental heritage. As early as 1832, the Piedmontese State had created a council of antiquities and fine arts (Giunta di antichità e Belle arti) and appointed Carlo Promis as its first inspector (Ispettore dei monumenti d’antichità dei reali Stati). This was in the same year that the government of France’s July Monarchy established a historic monuments commission, together with a post of inspector. As in France, from the outset, the Piedmontese monuments administration relied considerably on the help of local scholarly societies. The first inventory of historic buildings led to an initial list of ‘classified’ monuments enjoying statutory protection, which the French administration took over after 1860. The restoration project on the Roman Tropaeum Alpium, the Trophy of the Alps at La Turbie, may be seen as characteristic of this continuity, but whereas Sardinian civil engineers had advocated a simple consolidation of the structure, Viollet-le-Duc and his followers preferred their perspective of restitution of the monument. This new concept in restoration also entailed some revisions in the interpretation of history. The historic monuments and archaeological sites in Nice prior to 1860 were all heritage recognised as such under the regime of the House of Savoy. A new dynamic began to affect historic monuments after 1848 when the House of Savoy became involved in the process of Italian unification. The question of style became a highly political issue in Northern Italy, where architects of historicist inspiration sought to forge a national architectural style suitable for the new nation. With the French annexation of the County of Nice, the heritage acquired another national history, that of France. A fragment of a monument of antiquity was symbolically given to Napoleon III for the collections of the Museum of National Antiquities at Saint-Germain-en-Laye.
Interview with Amel Nafti, Managing Director of the école supérieure d’Art et de Design of Grenoble and Valence-ESAD Grenoble Valence since 2018. She mentions her work on the prints and artist’s ...editions collected and owned by the villa Arson, when she was Head of the Library and then Director of Studies and Research there. Today, she considers that the school history is an integral part of the school plan she is managing. She is coordinating with Pierre Oudart a working group devoted to the history of art schools within the Association of art schools, the ANDEA network.
The estimation of the seismic vulnerability of buildings at an urban scale, a crucial element in any risk assessment, is an expensive, time-consuming, and complicated task, especially in ...moderate-to-low seismic hazard regions, where the mobilization of resources for the seismic evaluation is reduced, even if the hazard is not negligible. In this paper, we propose a way to perform a quick estimation using convenient, reliable building data that are readily available regionally instead of the information usually required by traditional methods. Using a dataset of existing buildings in Grenoble (France) with an EMS98 vulnerability classification and by means of two different data mining techniques—association rule learning and support vector machine—we developed seismic vulnerability proxies. These were applied to the whole France using basic information from national databases (census information) and data derived from the processing of satellite images and aerial photographs to produce a nationwide vulnerability map. This macroscale method to assess vulnerability is easily applicable in case of a paucity of information regarding the structural characteristics and constructional details of the building stock. The approach was validated with data acquired for the city of Nice, by comparison with the RiskUE method. Finally, damage estimations were compared with historic earthquakes that caused moderate-to-strong damage in France. We show that due to the evolution of vulnerability in cities, the number of seriously damaged buildings can be expected to double or triple if these historic earthquakes were to occur today.
Pendimoun rock-shelter is among the oldest Neolithic sites known on the French littoral (Impressa culture, since ca. 5700
bce
). It was discontinuously occupied from the Mesolithic to the end of the ...Neolithic. During the Neolithic, it was used for pastoral purposes and domestic activities as well as for pottery production. Agriculture and cereal processing are clearly attested during the Impressa occupation (grains, husk and straw macroremains, grindstones) and become less obvious in the overlying layers. Phytolith analysis concerned 1 Mesolithic sample (Sauveterrian culture) and 16 samples covering most of the 6th millennium
bce
(Impressa, Cardial, and transition to Early Square Mouthed Pottery—SMP cultures). Significant amounts of grass phytoliths and the scarcity of dicot phytoliths suggest that the livestock, whose dung constitutes an important part of the sediment, mainly fed on wild grasses. Inflorescence bract phytoliths are well represented only in the Impressa levels, confirming that cereals were partly processed in situ only during the earliest stages of the Neolithic. Amounts of B
ilobate
short cells proved to be higher than expected in an area where only a few panicoid species can grow. The three candidates for B
ilobate
phytolith producers (
Setaria
spp.,
Digitaria sanguinalis
,
Echinochloa crus
-
galli
) all have a short vegetation cycle that lies entirely between the end of spring and the beginning of autumn, suggesting that the shelter was mainly used during that period. The low amount of inflorescence bract phytoliths (except during the Impressa) seems to restrict that range to the period before the ears become mature, namely the end of spring or early summer.
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