Spatial coherence of seismic wave fields across an alluvial valley (weak motion)     

Judith Riepl  Carlos Sousa Oliveira  Pierre-Yves Bard 《Journal of Seismology》1997,1(3):253-268

The loss of coherence of seismic waves, even over small distances, can become significant and consequently important for engineering applications. This coherence loss depends on several parameters (frequency, inter-station distance), but their dependencies are not well understood yet. We show the results of a detailed analysis of the spatial variability of the coherence between two signals. This analysis is based on a simple model which is an exponential function of inter-station distance and frequency. Data from a temporary network of 36 weak-motion instruments installed at the EURO-SEISTEST site, north-east of Thessaloniki (Greece), is used in this work. The data offers the unique possibility to study the loss of coherence over a wide range of distances, as the inter-station distances are between 8 m and 5488 m. We test the influence on the coherence of the length of the time-window of the signals, of the type of the waves present in the time-window and of the common energy of the signals. We also show that, at least at this particular site, the loss of coherence with distance is probably marked by a "cross over" distance, distinguishing two different ranges: one for inter-station distances up to 100 m and the other above 100 m. Finally, we find that the coherence determined from noise recordings behaves in a rather similar way to the one determined from coda-waves and more stationary (longer) signals. Therefore, noise can be useful for a rough, but quick estimation of the loss of coherence, at least for inter-station distances larger than 100 m.  相似文献   

Nonlinearity of one-dimensional creep characteristics of soft clays     

Qi-Yin Zhu  Zhen-Yu Yin  Pierre-Yves Hicher  Shui-Long Shen 《Acta Geotechnica》2016,11(4):887-900

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Evaluation of the influence of experimental conditions on H/V results from ambient noise recordings   总被引：5，自引：2，他引：3  

Jean-Luc Chatelain  Bertrand Guillier  Fabrizio Cara  Anne-Marie Duval  Kuvvet Atakan  Pierre-Yves Bard 《Bulletin of Earthquake Engineering》2008,6(1):33-74

The H/V-noise technique is now widely used to estimate site effect parameters (fundamental frequency and sometimes the associated soil amplification), and many surveys using this technique have provided convincing results. However, a general agreement on a methodology for data acquisition, data processing and result interpretation has yet to be found. H/V measurements from ambient noise recordings imply both reliability of the results and rapidity of data collection. It is therefore important to understand which experimental conditions (1) influence data quality and reliability, and (2) can help speeding up the recording process. Within the framework of the SESAME European project, a specific task was defined to investigate the reliability of the H/V spectral ratio technique in assessing the site effects. The aim of WP02, one specific Work Package of the SESAME project, is to study the effects of experimental conditions on both stability and reproducibility of H/V results. This study has been conducted in a purely experimental way, by testing the possible influence of various experimental conditions on H/V results both on the frequency peak value and on its amplitude. WP02 results help setting up the experimental conditions under which ambient noise recordings have to be performed in order to provide reproducible, reliable and meaningful H/V results. In this paper we present the results of the WP02 SESAME project concerning the evaluation of the influence of experimental conditions of ambient noise recording on H/V results.  相似文献   

Foreword     

Pierre-Yves Bard 《Bulletin of Earthquake Engineering》2008,6(1):1-2

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Internal erosion in dike-on-foundation modeled by a coupled hydromechanical approach     

Jie Yang  Zhen-Yu Yin  Farid Laouafa  Pierre-Yves Hicher 《国际地质力学数值与分析法杂志》2019,43(3):663-683

One of the major causes of instability in geotechnical structures such as dikes or earth dams is internal erosion, an insidious process that occurs over a long period of time. Research on this topic is still fairly new and much more needs to be understood in order to solve the problems posed by this phenomenon. This paper proposes a hydromechanical model based on porous continuous medium theory to assess how internal erosion impacts the safety of earthen structures. The saturated soil is considered as a mixture of four interacting constituents: soil skeleton, erodible fines, fluidized fine particles, and fluid. The detachment and transport of the fine particles are described by a mass exchange model between the solid and the fluid phases. An elastoplastic constitutive model for sand-silt mixtures has been developed to monitor the effect of the evolution of both porosity and fines content induced by internal erosion upon the behavior of the soil skeleton. The model has been numerically solved with the finite element method. It has then been applied to the specific case study of a dike foundation subjected to internal erosion induced by the presence of a karstic cavity beneath the alluvium layer. The numerical results show the onset of erosion, the time-space evolution of the eroded zone, and the hydromechanical response of the soil constituting the dike, all of which highlights the effects of the cavity location, the erosion rate, and the fines content.  相似文献   

Geophysical characterisation of karstic networks – Application to the Ouysse system (Poumeyssen,France)     

Roger Guérin  Jean-Michel Baltassat  Marie Boucher  Konstantinos Chalikakis  Pierre-Yves Galibert  Jean-François Girard  Valérie Plagnes  Rémi Valois 《Comptes Rendus Geoscience》2009,341(10-11):810-817

In the framework of the management of karstic aquifers, geophysical reconnaissance can be used to locate conduits and caves, and to characterise the surrounding limestone matrix. Suitable characterisation of heterogeneities in the karstic environment is, however, challenging for ground-based geophysical methods. The present article describes the results, and evaluates the response and accuracy of combined geophysical measurements carried out at the Poumeyssen test site in France, involving electrical resistivity imaging (ERI), magnetic resonance sounding (MRS), “mise-à-la-masse” electrical mapping, and seismic tomography. This site provides the opportunity to study a relatively wide, shallow, water-filled conduit whose location and shape are known from topographic work carried out by cave divers. Seismic and MRS provided the exact location and width of the conduit, to within a few meters. The seismic and electrical data suggest that the limestone medium surrounding the conduit is not homogeneous.  相似文献   

Eruptive response of oceanic islands to giant landslides: New insights from the geomorphologic evolution of the Teide-Pico Viejo volcanic complex (Tenerife, Canary)     

Thomas Boulesteix  Anthony Hildenbrand  Pierre-Yves Gillot  Vicente Soler 《Geomorphology》2012,138(1):61-73

Large sector collapses are a major component of oceanic islands evolution. Here we show that voluminous events such as the Icod landslide on Tenerife (Canary Islands) cause dramatic changes on the magma feeding system and control the subsequent volcanic and geomorphologic evolution of the eruptive complex over a period of more than 150 kyr. Instantaneous unloading by the Icod landslide is marked by the development of a large phonolitic explosive eruption dated at 175 ± 3 ka and interpreted as reflecting the immediate emptying of a shallow pre-existing magma chamber. Geochronological, geomorphological and geochemical analyses, carried out on the post-landslide volcanic succession sampled in a 4.4 km-long underground water-recovery gallery, provide further evidence for an enhanced extrusion of primitive lavas starting in the 10 kyr time interval following the failure. Rapid construction (< 40 kyr) of a thick basaltic volcano in the landslide scar at high eruptive rates (up to 8 km³ kyr⁻¹) increased the lithostatic pressure which then favored the intermittent storage of basic magma under the edifice. This resulted in more episodic construction evidenced by a significant decrease in output rates and the increasing occurrence of lavas with intermediate composition from 117 ± 7 to 52 ± 7 ka. An apparent volcanic gap is observed between 52 ± 7 and 18 ± 1 ka, after which highly differentiated lavas have been dominantly erupted. We propose that part of the gap can be explained by the individualization of a shallow magma reservoir a few kilometers below the base of the Teide volcano. During recent periods, vertical and lateral extrusions of trachytic and phonolitic viscous bodies from this storage area contributed to increase the slope of the main edifice up to 35°, overall favoring its present-day instability.  相似文献   

Detecting stratigraphical issues using direct radiocarbon dating from small-mammal remains     

Juan Rofes  Sophie Cersoy  Antoine Zazzo  Aurelien Royer  Pierre-Yves Nicod  Veronique Laroulandie  Mathieu Langlais  Yvan Pailler  Celine Leandri  Franck Leandri  Matthieu Lebon  Anne Tresset 《第四纪科学杂志》2020,35(4):505-513

Frequently preserved in archaeological and palaeontological sites, the tiny size of small-mammal remains favours percolations into underlying layers along stratigraphic sequences. This is one of the various post-depositional processes that may affect the integrity of the original deposits and therefore the subsequent scientific interpretations. Recent developments in sample preparation offer the possibility of detecting intrusive episodes through the absolute dating of minute amounts of bone (down to 10 mg), meaning that isolated elements (such as mandibles in this case) are sufficient to obtain reliable radiocarbon dates if collagen is moderately to well preserved. The radiocarbon dates obtained here for small-mammal bones (recovered from pre-Bølling to recent deposits) and their comparison with previous dates obtained from other sources (large-mammal bones, charcoal, botanical samples, etc.), with different protocols and instruments, illustrate the potential of small-mammal dating to reveal (and eventually contribute a solution to) stratigraphical issues in different archaeological contexts.  相似文献   

An integrated approach for catchment delineation and conduit-network modeling in karst aquifers: application to a site in the Swiss tabular Jura     

Arnauld Malard  Pierre-Yves Jeannin  Jonathan Vouillamoz  Eric Weber 《Hydrogeology Journal》2015,23(7):1341-1357

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The Piànico tephra: an early Middle Pleistocene record of intraplate volcanism in the Mediterranean     

Daniele L. Pinti  Xavier Quidelleur  Pierre Lahitte  Cyril Aznar  Sergio Chiesa  Pierre-Yves Gillot 《地学学报》2003,15(3):176-186

ABSTRACT Distal tephra are a valuable record of the volcano-tectonic evolution of an area under study. Here, we document the case of the Early Middle Pleistocene rhyolitic tephra of Piànico, discovered in the Southern Italian Alps. The geochemical characteristics of Piànico are unique among the distal tephra outcropping in Italy and indicate an intraplate volcanism at the source. The alkali composition and trace elements show a striking resemblance with the rhyolitic complex of the Euganean Hills, located 170 km from Piànico. However, these rhyolites are much older (Oligocene). Alternatively, the source of this intraplate volcanic episode could be located in the southern Tyrrhenian Sea.  相似文献