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Simulating strong ground motions produced by an earthquake is an important step to evaluate the seismic hazard of a region. The aim of this study is to provide an efficient tool for strong ground motions simulation. . To avoid the problem of unknown subsoil medium, we use the empirical Green's function technique. The ground motions are then obtained by summing the recordings of small earthquakes delayed between each other so as to reproduce the rupture propagation effects. The main problem of this study is to establish an appropriate summation scheme, which is able to generate realistic accelerograms in the time domain, and in agreement with scaling relationships (similarity relation and w~2 model) in the frequency domain. Using statistical methods, we avoid the main problems encountered classically in this kind of study. Finally, we establish two new methods of simulations : a purely stochastic method which requires the specification of only two parameters for the target event (seismic moment and stress drop) and a stochasto-kinematic method which is able to reproduce some of the kinematic rupture properties over the fault plane. These two methods are successfully tested on observed data (Mexico and Italy). Then, the stochastic method is applied to simulate the ground motion which could be produced by two moderate sized earthquakes in the French Riviera: a magnitude 5.7 onshore earthquake (10 km to the north of Nice) and a magnitude 6,3 offshore earthquake (25 km to the south of Nice). These simulations point out three important points: (1) the strong amplification effects in some sites in Nice, (2) the importance of the ground motion potentially produced by a magnitude 5.7 onsho re earthquake and (3) the major role played by the stress drop value of the potential earthquake.; Simuler les mouvements du sol produits par un séisme est une étape essentielle pour évaluer l'aléa sismique d'une région. L'objectif de cette étude est de fournir un code simple d'utilisation permettant de simuler de manière efficace les mouvements du sol. Pour s'affranchir de la connaissance du milieu de propagation, nous utilisons la technique des fonctions de Green empiriques. Les mouvements du sol sont alors reconstruits par la sommation des enregistrements de plusieurs petits séismes décalés dans le temps de manière à reconstituer le processus de rupture du gros séisme, La principale problématique de cette étude est la mise en place d'un schéma de sommation efficace permettant de générer des accélérogrammes réalistes dans le domaine temporel et en bon accord avec les lois d'échelles (loi de similitude et modèle en w~2) dans le domaine fréquentiel. Grâce à l'intégration de méthodes statistiques, nous évitons les problèmes majeurs rencontrés classiquement dans ce type d'étude. Nous aboutissons finalement à deux nouvelles méthodes de simulations: une méthode purement stochastique nécessitant la connaissance de seulement deux paramètres concernant le séisme cible (moment sismique et chute de contrainte) et une méthode stochasto-cinématique permettant de reproduire certaines propriétés cinématiques de la rupture sismique sur le plan de faille. Ces deux méthodes sont testées avec succès sur des données réelles (Mexique et Italie). La méthode stochastique est ensuite appliquée pour simuler les mouvements du sol susceptibles d'être produits par deux-séismes de magnitude modérée dans la région niçoise: un séisme de magnitude 5.7 à terre (10 km au nord de Nice) et un séisme de magnitude 6.3 en mer (25 km au sud de Nice). Ces simulations mettent en évidence trois points importants: (1) les forts effets d'amplifications sur certains sites à Nice, (2) l'importance des mouvements du sol susceptibles d'être produits par un séisme de magnitude 5.7 à terre et (3) le rôle majeur joué par la valeur de la chute de contrainte du séisme potentiel.

We present the results of a study of the subsurface tectonic features of the Basso Molise, Western Gargano and Northern Capitanata regions (Southern Italy) aimed at the identification of the source of the disastrous 1627 Gargano earthquake. In the maximum-damage area of this earthquake we have recognised a normal fault, here called the Apricena Fault, which has been identified as the fault that caused the seismic event. The Apricena Fault, striking WNW-ESE and dipping towards SSW, extends in the subsurface for about 30 kilometres from Serracapriola to Santa Maria di Stignano cutting through the whole Quaternary sequence. Other important tectonic structures trending WNW-ESE recognized in the area belong to an inactive Pleistocene strike-slip-fault system that is linked to the Mattinata Fault and to its offshore continuation in the Gondola-Grifone structural high. The Mattinata Fault and the Gondola-Grifone High form a quite complex structural feature whose kinematic behaviour is still matter of debate in the regional geological literature. NW-SE structural features recognized in the area are extensional faults whose activity was probably related to the late flexure-hinge retreat of the Adria plate margin during the Late Pliocene-Early Pleistocene eastward migration of the thrust belt-foredeep-foreland system.

On December 22nd, 1999 an earthquake of Magnitude Mw : 5.7 occurred at Ain Temouchent (northwest Algeria). This moderate seismic event was located in a region characterized by a low seismic activity where few historical events have been observed. The earthquake, with a maximum intensity of VII (MSK scale), caused serious damages to the Ain Temouchent city and its surroundings. In the epicentral area, 25 people died and about 25,000 people were made homeless. Some minor breaks have been observed in several areas in the field. They were mainly related to minor collapses in the landscape or in volcanic cavities. The focal mechanism has been studied by using broadband data at regional and teleseismic distances, and different methods. The fault-plane solution has been estimated from first motions of P wave. Depth and source time function have been estimated from the modeling of body waveforms. Scalar seismic moment and source dimension have been obtained from spectral analysis. Results show thrust motion, with a horizontal pressure axis oriented in a NW-SE direction, a depth of 4 km and a simple source time function with time duration of 5 s. Scalar seismic moment estimated from waveform modeling is 4.7 · 1017 Nm, and spectral analysis gives a value of 1.7 · 1017 Nm and a source radius of 7.5 km.

A new hybrid MS-BIE method based on the modal summation (MS) and the boundary integral equation (BIE) methods is developed. The proposed hybrid technique allows the theoretical seismogram synthesis taking into consideration seismic source properties, non-homogeneous wave path and local site effects as layering with non-parallel interfaces and free-surface topography. Each of the two techniques is applied in the part of the structural model where it works more efficiently. The MSM is applied for numerical simulation of wave propagation from the source position to the local region of interest, while the BIEM is used inside the local multi-layered geological region. The accuracy and validation study of the proposed method is presented by solution of numerical examples simulation different seismic scenarios. The comparison between the MS-BIEM synthetic seismograms and ones obtained by pure analytical and/or other hybrid methods has been evaluated and discussed.

Em aplicações ligadas à área de engenharia civil, o ensaio "crosshole" (entre furos) é o método mais utilizado para determinação das propriedades elásticas dos maciços por intermédio da medida das velocidades de propagação das ondas P e S. Por outro lado, seu uso tem sido limitado somente a grandes obras, devido principalmente, aos custos envolvidos na sua execução. Isto é devido, principalmente, à necessidade da perfuração de furos especiais para acomodar os equipamentos utilizados. Com vistas a diminuir tais custos, foi desenvolvida uma fonte sísmica, de pequeno diâmetro e de baixo custo, possível de ser utilizada nos furos de sondagem normalmente executados para os ensaios SPT (Standard Penetration Test), durante a fase de investigação em solos. O diâmetro externo máximo desta fonte é de 40 mm, o que permite instalá-la em revestimentos com 50 mm de diâmetro externo (46 mm interno). Dessa forma, o revestimento pode ser facilmente instalado em furo com 75 mm (3") de diâmetro máximo, permitindo, também, o preenchimento do espaço anelar com calda de cimento. A fonte sísmica é fixada na parede do revestimento por meio de um sistema pneumático e, por meio de um êmbolo deslizante gera principalmente ondas S. O uso dessa fonte em diversas obras tem evidenciado sua praticidade devida mormente ao seu pequeno tamanho e baixo peso. In civil engineering applications, the crosshole test is the most utilized method to determine the propagation velocities of in situ P and S waves of the different strata and, consequently, to calculate the dynamic elastic parameters of rock or soil samples. Otherwise, its use has been limited just to very important studies since the associated cost is very high for smaller constructions such as residential and ordinary buildings. This is mainly due to the fact that the equipment normally used to perform these tests needs special boreholes, with diameter uncommon in the investigation phase. In order to decrease the crosshole overall cost, a simple and inexpensive seismic source was developed. This source can be used in the same boreholes made during the standard penetration test (SPT). Its maximum external diameter is 40 mm, fitting in a PVC casing of 50 mm external diameter (46 mm internal). At the same time, the casing can be easily installed in a 75 mm (3") maximum diameter, leaving place to fill the annular space with mortar. The seismic source clamps on the borehole wall by a pneumatic system and, by means of a sliding piston, generates mainly S type waves. It has proven to be easy to use besides being lightweight and of small size.

This work presents seismic source studies using near?field data. In accordance with the quality and the quantitv of available data we developped and applied various methods to characterize the seismic source. Macroseismic data are used to verify if simple and robust methods used on recent instrumental earthquakes may provide a good tool to calibrate historical events in France. These data are often used to characterize earthquakes to be taken into account for seismic hazard assessment in moderate seismicity regions. Geodetic data (SAR, GPS) are used to estimate the slip distribution on the fault during the 1992, Landers, California earthquake. These data are also used to precise the location and the geometry of the main events of the 1997, Colfiorito, central Italy, earthquake sequence. Finally, the strong motions contain the most complete information about rupture process. These data are used to discriminate between two possible fault planes of the 1999, north India, Chamoli earthquake. The strong motions recorded close to the 1999, Mexico, Oaxaca earthquake are used to constrain the rupture history. Strong motions are also used in combination with geodetic data to access the rupture history of the Landers earthquake and the main events of the Colfiorito seismic sequence. For the Landers earthquake, the data quality and complementarity offered the possibility to describe the rupture development with accuracy. The large heterogeneities in both slip amplitude and rupture velocity variations suggest that the rupture propagates by breaking successive asperities rather than by propagating like a pulse at constant velocity. The rupture front slows as it encounters barriers and accelerates within main asperities., Ce travail est consacré à l'étude de la source sismique en utilisant des données de champ proche. Selon la quantité et la qualité des données disponibles, nous avons appliqué différentes méthodes pour caractériser la rupture sismique. Nous avons, tout d'abord, validé des méthodes macrosismiques sur des séismes français récents. Ces données permettent d'estimer la localisation et la taille des séismes historiques et sont utilisées pour caractériser les séismes à prendre en compte lors de l'évaluation de l'aléa dans des régions à sismicité modérée. Les données géodésiques (SAR, GPS) nous ont permis d'estimer la distribution du glissement sur la faille lors du séisme californien de Landers (1992). Ces données nous ont permis de préciser la localisation et la géométrie des failles ayant joué lors des principaux événements de la séquence sismique italienne de Colfiorito (1997). Enfin les données de mouvement fort nous ont permis d'estimer le pendage de la faille ayant rompu lors du séisme indien de Chamoli (1999). Nous avons utilisé des données de mouvement fort pour contraindre le développement de la rupture lors du séisme mexicain de Oaxaca (1999). Les données de mouvement fort ont été utilisées en association avec des données géodésiques pour remonter au développement temporel de la rupture lors du séisme de Landers et de la séquence sismique de Colfiorito. En ce qui concerne le séisme de Landers, la qualité et la complémentarité des données nous ont permis d'obtenir un véritable film du glissement. La rupture est hétérogène. On note la présence de zones où le glissement est plus important qu'ailleurs. Ces zones sont séparées par des régions qui correspondent aux zones de relais entre les segments de faille où le glissement est moindre et où la vitesse de rupture diminue.

Mongolia characterize the transition between compressive structures associated with India-Asia collision and extensive structures from Baykal rift. It suffered, since 1905, four earthquakes with magnitude larger then 8, (Tsetserleg, Bolnay, Fu Yun and Gobi-Altay). Ruptures associated with those earthquakes draw up a parallelogram composed by senestral strike slip faults on an east-west direction and dextral strike slip faults on NNW-SSE direction. Inside this parallelogram, the Hangay dome is associated with normal faults and recent alkaline volcanism. The source history of these two 1905 earthquakes shows a predominating propagation of the rupture to the east. The Tsetserleg earthquake ruptures (Mw = 7,95 ± 0,02.) may continue beyond the mapped ruptures. The nucleation of Bolnay earthquake (Mw = 8,4 ± 0,1) took place at the intersection between the main fault and the Teregtiin fault. Ruptures associated with the Gobi-Altay earthquake are complexes and run along the Ikhe Bogdo massif which rotate counterclockwise (24° ± 11° ) since the Miocene. Time recurrence on this fault is around 5000 years with a rate of around 1 mm/year. The displacement on the Altay and Gobi-Altay conjugates strike slip faults is absorbed on reverse faults, the whole creating compressive wedge. The Hangay dome results from the combination between a mantel up welling and the compressive front associated with India-Asia collision. The Hangay dome rotate clockwise. The sismicity characterize late aftershocks associated with recent earthquakes. These aftershocks are numerous on segments with vertical slip and few on strike slip segments. A compression oriented N20 ± 10° can explain all deformations indicating the actual preponderance of the compressive front associated to India-Asia collision, preceded by a mantel episode which prepared the region. We propose a model of pure deformation combined with a clockwise rotation in Mongolia., La Mongolie caractérise la transition entre les structures compressives liées à la collision Inde-Asie et extensives du rift du Baïkal. Elle a connu depuis 1905 quatre séismes de magnitude supérieure ou égale à 8, (Tsetserleg, Bolnaï, Fu Yun et Gobi-Altaï). Les ruptures associées à ces événements forment un parallélogramme composé par des failles décrochantes sénestres est-ouest et décrochantes dextres NNO-SSE. Au centre, le dôme du Hangaï est associé à des failles normales et à un volcanisme alcalin récent. L'étude de la source des deux séismes de 1905 indique une propagation dominante des ruptures vers l'est. Le séisme de Tsetserleg (Mw = 7,95 ± 0,02.) aurait continué au-delà des ruptures cartographiées. L'initiation du séisme de Bolnaï (Mw = 8,4 ± 0,1) s'est faite à l'intersection entre la faille principale et celle de Teregtiin. Les ruptures associées au séisme du Gobi-Altaï sont complexes et bordent le massif de Ikhe Bogdo qui subit une rotation antihoraire (24° ± 11° ) depuis le Miocène. L'intervalle de récurrence sur cette faille est d'environ 5000 ans avec une vitesse d'environ 1 mm/an. Le mouvement sur les failles décrochantes conjuguées de l'Altaï et du Gobi-Altaï est amorti sur des failles inverses, l'ensemble formant des coins en compression. La formation du dôme du Hangaï est le résultat d'une combinaison entre un panache mantélique et du front compressif lié à la collision Inde-Asie. Le massif subit une rotation horaire. La sismicité correspond à des répliques tardives des séismes récents plus nombreuses sur les segments à rejet vertical que décrochants. Une compression orientée N20 ± 10° permet d'expliquer toutes les déformations indiquant la prépondérance actuelle du front compressif associé à la collision Inde-Asie, précédée d'un épisode mantélique qui a préparé la région. Nous proposons un modèle de déformation pure combinée avec une rotation horaire pour la Mongolie.

Unrapport de thèse + une carte AO; Mongolia characterize the transition between compressive structures associated with India-Asia collision and extensive structures from Baykal rift. It suffered, since 1905, four earthquakes with magnitude larger then 8, (Tsetserleg, Bolnay, Fu Yun and Gobi-Altay). Ruptures associated with those earthquakes draw up a parallelogram composed by senestral strike slip faults on an east-west direction and dextral strike slip faults on NNW-SSE direction. Inside this parallelogram, the Hangay dome is associated with normal faults and recent alkaline volcanism. The source history of these two 1905 earthquakes shows a predominating propagation of the rupture to the east. The Tsetserleg earthquake ruptures (Mw = 7,95 ± 0,02.) may continue beyond the mapped ruptures. The nucleation of Bolnay earthquake (Mw = 8,4 ± 0,1) took place at the intersection between the main fault and the Teregtiin fault. Ruptures associated with the Gobi-Altay earthquake are complexes and run along the Ikhe Bogdo massif which rotate counterclockwise (24° ± 11° ) since the Miocene. Time recurrence on this fault is around 5000 years with a rate of around 1 mm/year. The displacement on the Altay and Gobi-Altay conjugates strike slip faults is absorbed on reverse faults, the whole creating compressive wedge. The Hangay dome results from the combination between a mantel up welling and the compressive front associated with India-Asia collision. The Hangay dome rotate clockwise. The sismicity characterize late aftershocks associated with recent earthquakes. These aftershocks are numerous on segments with vertical slip and few on strike slip segments. A compression oriented N20 ± 10° can explain all deformations indicating the actual preponderance of the compressive front associated to India-Asia collision, preceded by a mantel episode which prepared the region. We propose a model of pure deformation combined with a clockwise rotation in Mongolia.; La Mongolie caractérise la transition entre les structures compressives liées à la collision Inde-Asie et extensives du rift du Baïkal. Elle a connu depuis 1905 quatre séismes de magnitude supérieure ou égale à 8, (Tsetserleg, Bolnaï, Fu Yun et Gobi-Altaï). Les ruptures associées à ces événements forment un parallélogramme composé par des failles décrochantes sénestres est-ouest et décrochantes dextres NNO-SSE. Au centre, le dôme du Hangaï est associé à des failles normales et à un volcanisme alcalin récent. L'étude de la source des deux séismes de 1905 indique une propagation dominante des ruptures vers l'est. Le séisme de Tsetserleg (Mw = 7,95 ± 0,02.) aurait continué au-delà des ruptures cartographiées. L'initiation du séisme de Bolnaï (Mw = 8,4 ± 0,1) s'est faite à l'intersection entre la faille principale et celle de Teregtiin. Les ruptures associées au séisme du Gobi-Altaï sont complexes et bordent le massif de Ikhe Bogdo qui subit une rotation antihoraire (24° ± 11° ) depuis le Miocène. L'intervalle de récurrence sur cette faille est d'environ 5000 ans avec une vitesse d'environ 1 mm/an. Le mouvement sur les failles décrochantes conjuguées de l'Altaï et du Gobi-Altaï est amorti sur des failles inverses, l'ensemble formant des coins en compression. La formation du dôme du Hangaï est le résultat d'une combinaison entre un panache mantélique et du front compressif lié à la collision Inde-Asie. Le massif subit une rotation horaire. La sismicité correspond à des répliques tardives des séismes récents plus nombreuses sur les segments à rejet vertical que décrochants. Une compression orientée N20 ± 10° permet d'expliquer toutes les déformations indiquant la prépondérance actuelle du front compressif associé à la collision Inde-Asie, précédée d'un épisode mantélique qui a préparé la région. Nous proposons un modèle de déformation pure combinée avec une rotation horaire pour la Mongolie.

The primary problem to carry out Seismic While Mining is whether the seismic signals, induced by vibration of mining machines, can be useful seismic sources. Firstly, this paper describes the seismic signals near filed induced by the shearer, boring machine and pneumatic drill respectively, and the signal features in time domain, frequency domain, autocorrelation functions. Secondly, shows the features of far field seismic signal emitted by the shearer, and the seismic interferometry of the record also is done. The result shows that the signal from the shearer is stronger in 1-400 Hz, and contained pulses and periodic compositions, in line with the characteristics of the shearer mining; far field signal of the shearer is mixed with microseisms; the single-shot record can gain from the far field shearer signal via deconvolution and correlation, and the seismic features of the shearer and microseisms are similar; seismic signals emitted from the boring machine and pneumatic drill also have broad band features. The experiential studies suggest that the vibration signals induced by the mining machines can be seismic sources.

Some earthquake models based on the elastic theory of dislocations are presented. Earthquake occurrence is modelled as the opening of a crack in an infinite elastic medium triggered by the action of localized stress distributions. The fracture is modelled as a continuum of infinitesimal dislocations. This approach allows us to have complete information about the stress field and the displacement field and to make a first step towards understanding the relation between source mechanism and stress distributions.

In light of the recent enhanced activity in the study of tsunami waves and their source mechanisms, we consider tsunami-like waves that are induced by atmospheric processes rather than by seismic sources. These waves are mainly associated with atmospheric gravity waves, pressure jumps, frontal passages, squalls and other types of atmospheric disturbances, which normally generate barotropic ocean waves in the open ocean and amplify them near the coast through specific resonance mechanisms (Proudman, Greenspan, shelf, harbour). The main purpose of the present study is to describe this hazardous phenomenon, to show similarities and differences between seismic and meteorological tsunamis and to provide an overview of meteorological tsunamis in the World Ocean. It is shown that tsunamis and meteotsunamis have the same periods, same spatial scales, similar physical properties and affect the coast in a comparably destructive way. Some specific features of meteotsunamis make them akin to landslide-generated tsunamis. The generation efficiency of both phenomena depend on the Froude number (Fr), with resonance taking place when Fr∼1.0. Meteotsunamis are much less energetic than seismic tsunamis and that is why they are always local, while seismic tsunamis can have globally destructive effects. Destructive meteotsunamis are always the result of a combination of several resonant factors; the low probability of such a combination is the main reason why major meteotsunamis are infrequent and observed only at some specific locations in the ocean.

The three largest events of the 1997 Umbria-Marche (Italy) sequence occurred on September 26, 1997 at 00:33 GMT (Event 1, MW=5.7) and 09:40 GMT (Event 2, MW=6.0) in the Colfiorito area and on the October 14, 1997 at 15:23 (Event 3, MW=5.6) in the Sellano area. The availability of different sets of geodetic and seismological data allowed several studies to characterize the extended sources of events 1-3. In this work, I review some of the studies that obtain the properties of the seismic sources by inversion of available data. Generally these studies assume the seismic sources as dislocations or distributions of equivalent point sources in elastic half-spaces. Following their chronological order, they model increasing complexities of the sources by using an increasing number of data. Some of the differences between results obtained, such as the top edge depth estimates, are shown to be due to the different approaches used. Commonly a 1-D crustal model is used in inverting strongmotion data. Instead homogeneous elastic half-spaces are mainly assumed in inverting geodetic data to obtain the three main sources of the 1997 Umbria-Marche sequence. Assuming the same crustal structure is important to make comparable results obtained analyzing seismological data or geodetic data separately, as it has been done till now for this sequence.