Global oceanic microseism sources as seen by seismic arrays and predicted by wave action models.

International audienceWe analyze global microseism excitation patterns between July 2000 and June 2001. Seismological observations are compared with modeling results to isolate robust activity features of relevant source processes. First, we use observations of microseism source locations estimated by Landès et al. (2010) based on array processing of ambient noise correlations. Second, we construct synthetic activity patterns by coupling sea state estimates derived from wave action models to the excitation theory for microseisms. The overall spatiotemporal evolution of both estimates is characterized by a seasonal character that is associated with strong activity during winter months. The distribution of landmass causes seasonal changes on the Northern Hemisphere (NH) to exceed the variability on the Southern Hemisphere (SH). Our systematic comparison of the two estimates reveals significant microseism excitation along coastlines and in the open ocean. Since coastal reflections are not accounted for in the modeling approach, the consistent mismatch between near-coastal observations and predictions suggests that relevant microseism energy arriving at the networks is generated in these areas. Simultaneously, systematic coincidence away from coastlines verifies the open ocean generation hypothesis. These conclusions are universal and robust with respect to the seismic network locations on the NH. The spatially homogeneous resolution of our synthetics provides a valuable resource for the assessment of the global microseism weather. Similar to previously identified hot spot areas in the North Atlantic, the modeled distributions hypothesize regions of strong localized activity on the SH, which are only partially confirmed by the analyzed data sets

Anatomy of the high-frequency ambient seismic wave field at the TCDP borehole.

International audienceThe Taiwan Chelungpu-fault Drilling Project (TCDP) installed a vertical seismic array between 950 and 1270 m depth in an active thrust fault environment. In this paper we analyze continuous noise records of the TCDP array between 1 and 16 Hz. We apply multiple array processing and noise correlation techniques to study the noise source process, properties of the propagation medium, and the ambient seismic wave field. Diurnal amplitude and slowness patterns suggest that noise is generated by cultural activity. The vicinity of the recording site to the excitation region, indicated by a narrow azimuthal distribution of propagation directions, leads to a predominant ballistic propagation regime. This is evident from the compatibility of the data with an incident plane wave model, polarized direct arrivals of noise correlation functions, and the asymmetric arrival shape. Evidence for contributions from scattering comes from equilibrated earthquake coda energy ratios, the frequency dependent randomization of propagation directions, and the existence of correlation coda waves. We conclude that the ballistic and scattered propagation regime coexist, where the first regime dominates the records, but the second is weaker yet not negligible. Consequently, the wave field is not equipartitioned. Correlation signal-to-noise ratios indicate a frequency dependent noise intensity. Iterations of the correlation procedure enhance the signature of the scattered regime. Discrepancies between phase velocities estimated from correlation functions and in-situ measurements are associated with the array geometry and its relative orientation to the predominant energy flux. The stability of correlation functions suggests their applicability in future monitoring efforts

Intensity-based sentiment analysis. The 2020 Aegean earthquake.

After an earthquake, it is necessary to understand its impact to provide relief and plan recovery. Social media (SM) and crowdsourcing platforms have recently become valuable tools for quickly collecting large amounts of first-hand data after a disaster. Earthquake-related studies propose using data mining and natural language processing (NLP) for damage detection and emergency response assessment. Using tex-data provided by the Euro-Mediterranean Seismological Centre (EMSC) collected through the LastQuake app for the Aegean Earthquake, we undertake a sentiment and topic analysis according to the intensities reported by their users in the Modified Mercalli Intensity (MMI) scale. There were collected 2,518 comments, reporting intensities from I to X being the most frequent intensity reported III. We use supervised classification according to a rule-set defined by authors and a two-tailed Pearson correlation to find statistical relationships between intensities reported in the MMI by LastQuake app users, polarities, and topics addressed in their comments. The most frequent word among comments was: “Felt.” The sentiment analysis (SA) indicates that the positive polarity prevails in the comments associated with the lowest intensities reported: (I-II), while the negative polarity in the comments is associated with higher intensities (III–VIII and X). The correlation analysis identifies a negative correlation between the increase in the reported MMI intensity and the comments with positive polarity. The most addressed topic in the comments from LastQuake app users was intensity, followed by seismic information, solidarity messages, emergency response, unrelated topics, building damages, tsunami effects, preparedness, and geotechnical effects. Intensities reported in the MMI are significantly and negatively correlated with the number of topics addressed in comments. Positive polarity decreases with the soar in the reported intensity in MMI demonstrated the validity of our first hypothesis, despite not finding a correlation with negative polarity. Instead, we could not prove that building damage, geotechnical effects, lifelines affected, and tsunami effects were topis addressed only in comments reporting the highest intensities in the MMI

Intensity-based sentiment and topic analysis. The case of the 2020 Aegean Earthquake

After an earthquake, it is necessary to understand its impact to provide relief and plan recovery. Social media (SM) and crowdsourcing platforms have recently become valuable tools for quickly collecting large amounts of first-hand data after a disaster. Earthquake related studies propose using data mining and natural language processing (NLP) for damage detection and emergency response assessment. Using tex-data provided by the Euro-Mediterranean Seismological Centre (EMSC) collected through the LastQuake app for the Aegean Earthquake, we undertake a sentiment and topic analysis according to the intensities reported by their users in the Modified Mercalli Intensity (MMI) scale. There were collected 2,518 comments, reporting intensities from I to X being the most frequent intensity reported III. We use supervised classification according to a rule-set defined by authors and a two-tailed Pearson correlation to find statistical relationships between intensities reported in the MMI by LastQuake app users, polarities, and topics addressed in their comments. The most frequent word among comments was: “Felt.” The sentiment analysis (SA) indicates that the positive polarity prevails in the comments associated with the lowest intensities reported: (I-II), while the negative polarity in the comments is associated with higher intensities (III–VIII and X). The correlation analysis identifies a negative correlation between the increase in the reported MMI intensity and the comments with positive polarity. The most addressed topic in the comments from LastQuake app users was intensity, followed by seismic information, solidarity messages, emergency response, unrelated topics, building damages, tsunami effects, preparedness, and geotechnical effects. Intensities reported in the MMI are significantly and negatively correlated with the number of topics addressed in comments. Positive polarity decreases with the soar in the reported intensity in MMI demonstrated the validity of our first hypothesis, despite not finding a correlation with negative polarity. Instead, we could not prove that building damage, geotechnical effects, lifelines affected, and tsunami effects were topis addressed only in comments reporting the highest intensities in the MMI

Matched Field Processing of Three-Component Seismic Array Data Applied to Rayleigh and Love Microseisms

We extend three component plane wave beamforming to a more general form and devise a framework which incorporates velocity heterogeneities of the seismic propagation medium and allows us to estimate accurately sources which do not follow the simple plane wave assumption. This is achieved by utilising fast marching to track seismic wave fronts for given surface wave phase velocity maps. The resulting matched field processing approach is used to study the surface wave locations of Rayleigh and Love waves at 8 and 16 seconds based on data from four seismic arrays in the western USA. By accurately accounting for the path propagation effects, we are able to map microseism surface wave source locations more accurately than conventional plane wave beamforming. In the primary microseisms frequency range, Love waves are dominant over Rayleigh waves and display a directional radiation pattern. In the secondary microseisms range, we find the general source regions for both wave types to be similar, but on smaller scales differences are observed. Love waves are found to originate from a larger area than Rayleigh waves and their energy is equal or slightly weaker than Rayleigh waves. The energy ratios are additionally found to be source location dependent. Potential excitation mechanisms are discussed which favour scattering from Rayleigh‐to‐Love waves

Origin of deep ocean microseisms by using teleseismic body waves.

International audienceRecent studies of oceanic microseisms have concentrate on fundamental-mode surface waves. Extraction of fundamental-mode Rayleigh and Love wave Green functions from station-station correlations of ambient seismic noise has recently been demonstrated to be a very powerful tool for imaging of the Earth's crust and uppermost mantle. In this study we concentrate on energetic arrivals in two frequency bands around the primary (14s) and the secondary (7s) microseismic peaks that appear at near-zero times in noise cross-correlations. Thanks to a polarisation analysis of data from the the ETSE network (Turkey), we identify this "near-zero time" signal as an upcoming P wave in the secondary microseismic frequency band (5-10s). In a second step, analysing noise cross-correlations from three different arrays ( in Yellowstone, in Turkey and in Kyrgyzstan), we determine the origin of these signals by means of beamforming analysis and its projection on the Earth. Our results show that, in the 0.1-0.3 Hz frequency band, the energetic "near-zero" time arrivals in seismic noise cross-correlations are mainly formed by teleseismic P, PP, and PKP waves. Generation of this ambient body waves in the secondary microseismic band presents a marked seasonal behaviour with sources located in southern and northern oceans during summer and winter, respectively. Moreover, body wave array analysis is accurate enough to confirm that significant amount of the microseism energy is generated far from the coast in deep oceans

Fedasil, une institution vue et vécue par ses résidents adultes et enfants.

Ce mémoire, réalisé dans le cadre du master en Anthropologie, finalité interculturalité et développement, porte sur le vécu des résidents adultes et des résidents enfants, dans un centre d’accueil pour demandeurs d’asile, institution gouvernementale ; le Petit-Château à Bruxelles. Une comparaison est faite entre ces deux vécus, celui des résidents adultes, donc des pères, des mères de famille, des adultes « accomplis », et celui des enfants et jeunes, encore dans une période de construction identitaire et physique, la période de l’enfance.Master [120] en anthropologie, Université catholique de Louvain, 201

Organisation conceptuelle de l'activité d'adaptation du psychomotricien : une approche par le sensible de l'analyse de l'activité dans une perspective de didactique professionnelle.

Psychomotor therapists belong to the category of the professions of the relation. The perspective of this profession and its conceptual field in which it is anchored differ from those related with an activity of production; This professional activity is entirely characterized by its interactional nature. The approaches of psychomotor therapists are at the intersection of therapy, rehabilitation and/or education. Originally addressed to children with a compromised development, those practices are now relevant to people of all ages, from the healthy to sick subjects as well as to subjects having circumstantial difficulties. The scope of the field of competence and the extension of the fields of intervention leads us to question the specificity of the activity of the psychomotor therapist while he intervenes with his patients or his partners of working session. Our research focuses on the analysis of this professional activity. The matter is not to study the work or to describe the job. The way of he realizes his activity in situation of intervention and the way he organize its spatial and temporal development are what we attempt to understand. In the processes of conceptualization that underlie the conduct of one's activity in a situation, there are forms of invariant organization of one's activity, concepts that organize it.Our research takes place in the theoretical framework of adult learning, i.e. professional didactics. Our analysis is based on an interactional and multimodal approach of the professional activity, an approach through the sensible. In this activity appears a specific structure of development that we call "choregraphical strategy". It comes in an organizational dynamic underlied by the implementation of a specific pattern, that we call “sens of balance pattern”. Composition, moderation and flexibility characterize it. Our research contains issues related to professional training. It also includes opportunities for professional development.Le métier de psychomotricien appartient à la catégorie des métiers dits « de la relation ». La perspective dans laquelle s’inscrit ce travail, le cadre conceptuel dans lequel il s’ancre, diffèrent donc de ceux propres à une activité de production : son travail se caractérise par sa nature interactionnelle. Les pratiques des psychomotriciens sont à la croisée de la thérapie, de la rééducation et de l'éducation. Elles concernent les personnes de tous les âges, allant du sujet sain au sujet malade en passant par celui rencontrant des difficultés circonstancielles. L’étendue du champ de compétences et l’extension des domaines d’intervention nous amènent à poser la question de la spécificité de l’activité du psychomotricien en situation d’interaction avec ses patients ou avec ses partenaires de séance. Notre recherche porte sur l’analyse de cette activité professionnelle. Il ne s’agit pas d’étudier son travail ou de décrire son emploi. Son activité, telle qu’il la réalise en situation d’intervention et telle qu’il l’organise au cours de son développement spatial et temporel, est la dimension de son métier que nous cherchons à comprendre. Dans les processus de conceptualisation sous-jacents à la conduite de son activité en situation opèrent des formes d’organisation invariante de son activité et des concepts organisateurs de cette activité. Le cadre théorique dans lequel s’ancre notre démarche est celui de la didactique professionnelle. Notre analyse se fonde sur une approche interactionnelle et multimodale de l’activité professionnelle, une approche de l’activité par le sensible. Il apparaît dans cette activité une forme de développement spécifique que nous appelons "stratégie chorégraphique". Elle se décline dans une dynamique organisationnelle sous-tendue par la mise en œuvre d’un schème spécifique, celui que nous nommons « le sens de l’équilibre ». Composition, mesure et souplesse le caractérisent.Notre recherche recèle des enjeux relatifs à la formation professionnelle. Elle comporte également des perspectives de développement professionnel