Papers by El Hadi Oubaiche
114 p. : ill. ; 30 cmParmi les nombreuses méthodes d'évaluation des effets de site, la plus p... more 114 p. : ill. ; 30 cmParmi les nombreuses méthodes d'évaluation des effets de site, la plus précise est basée sur l'enregistrement de séismes, ce qui nécessite des réseaux accélérographiques denses et l'attente d'un séisme. Mais, la prévention ne permet pas d'attendre, et nous sommes contraints d'évaluer les effets de sites à partir de simulations numériques, en utilisant des modèles de vitesses obtenus par prospection sismique.Les modèles de vitesses auxquels nous nous intéressons dans l'évaluation des effets de sites sont définis par les vitesses de l'onde de cisaillement et l'épaisseur des sédiments entre le rocher sismique et la surface du sol. Le programme SHAKE (Schnabel et al., 1972) version modifiée SHAKE91 (Idriss and Sun, 1992) utilisé dans ce travail permet de montrer que l'amplification du mouvement sismique est étroitement liée à ces deux paramètres, d'où l'intérêt d'étudier l'apport des différents méthodes de pros...
A rainfall-induced deep large landslide occurred on March 12, 2012, in the city of Azazga (northe... more A rainfall-induced deep large landslide occurred on March 12, 2012, in the city of Azazga (northern Algeria) causing heavy damages to residential buildings and public infrastructures. In this work, we investigate the inventory mapping, deformation characteristics, the controlling factors and the failure mechanisms of this landslide based on field investigation, aerial photographs/satellite images interpretation, deep boreholes equipped with piezometers and inclinometers as well as subsurface geophysical imaging by Electric Resistivity Tomography (ERT). The obtained landslide inventory map shows that the landslide of March 2012, affected an area of 0,40 km2. This landslide is considered as partial reactivations of large pre-existing one (0,606 km2) which represents 6,65 % of the total urban area. Moreover, the analyses identified two types of involved causative factors: (i) the triggering factor related to the antecedent rainfall and human activity through slope excavations and emban...
9th Congress of the Balkan Geophysical Society, 2017
Summary This presentation reviews the new data; from both geophysical and geological investigatio... more Summary This presentation reviews the new data; from both geophysical and geological investigations, carried out through the Sidi-Abdellah microzoning project. As a whole, data indicate that the Mahelma Fault would be an earlier normal fault of the Mitidja basin. During basin inversion, this fault would have been reactivated recording reversal of movement from extension to reverse. This fault has attracted attention largely because its economic implication related to seismic hazard assessment, and because the Mahelma fault can inform us about the active tectonic of the major Sahel active fault.
During a month, a continuous survey of ambient vibrations has been carried out on the Algerian Na... more During a month, a continuous survey of ambient vibrations has been carried out on the Algerian National Center for Applied Research in Paraseismic Engineering (CGS) building, located in Algiers, Algeria. Providing data over ten synchronous sensors (five at the roof, four on the vertical of the building (more one on the roof) and one outside the building, on soil), it has been continuously monitored three different dynamic parameters of this building: the fundamental frequencies (in both directions of the building), their corresponding damping and their corresponding modal shape. This work underlines that both fundamental frequency and damping fluctuations (day-night variations) are linked one to another and not linked to the energy assessed in the building (or to the small strain generated by ambient vibrations) due to a too long delay between the frequency-damping maxima and the maxima of the energy assessed inside the building. However, it is strongly suspected a relationship betw...
World Academy of Science, Engineering and Technology, International Journal of Civil and Environmental Engineering, 2016
Arabian Journal of Geosciences, 2020
The Mahelma fault, located upon the Sahel anticline at the tip of the major Sahel fault, is often... more The Mahelma fault, located upon the Sahel anticline at the tip of the major Sahel fault, is often suspected to be a secondary structure. Yet, to date, the Mahelma fault has displayed no definitive evidences for faulting activity and no unambiguous typology. This paper reviews new data, especially geological and subsurface data, acquired through the Algiers west microzoning project. The data indicate that (1) the Mahelma fault is an antithetic high-angle reverse fault, (2) the interpreted dip is around 80°t oward the SSE and thus implies a North-verging fault, and (3) the fault zone has been observed in several fault sites and allowed direct observation of fault displacements and fault throws. (4) Displacements directly related to the Mahelma fault affect clearly young sediments including consolidated Quaternary sands. We suggest that the Mahelma fault forms an active backthrust originating from pre-existing normal fault with a possible linkage and interaction with the major Sahel forethrust. We conclude from the foregoing that the Mahelma fault most likely ruptures in concert with earthquakes on the Sahel main fault. The results also point the activity of the Sahel fault-related fold and hence complicate earthquake hazard analyses.
Bulletin of Engineering Geology and the Environment, 2019
This paper deals with the contribution of the ambient vibration horizontal-to-vertical spectral r... more This paper deals with the contribution of the ambient vibration horizontal-to-vertical spectral ratio (HVSR) method in soil engineering studies, particularly in backfill compactness assessment. The study is based on 60 ambient vibration recordings performed in 2015 at the container terminal of Algiers harbor, subjected a year before to a geotechnical study based on 23 boreholes and 13 cone penetration tests (CPT) for backfill improvement. To highlight the contribution of the HVSR method, the results of the geotechnical and HVSR studies are first analyzed separately and then in combination. The HVSR method provides a compactness zonation map based on peak amplitude variation. Both methods define the same pattern: a southern section where the backfill is more compact, and a northern section where the backfill is less compact. This shows that the HVSR peak amplitudes are sensitive to compactness variations, which may be sufficient for qualitative zonation. In addition, with the combination of the two methods, rough estimations of shear-wave velocity and thickness of the backfill can be retrieved. This study shows that the HVSR method can be a very useful investigative tool in soil engineering studies. When the HVSR method is deployed before any conventional technique, a geotechnical investigation campaign can be significantly optimized. Moreover the combined interpretation brings complementary quantitative soil information.
Journal of Earthquake Engineering, 2018
The ambient vibration horizontal-to-vertical spectrum method (HVSR) is widely used in microzonati... more The ambient vibration horizontal-to-vertical spectrum method (HVSR) is widely used in microzonation and structural studies, assuming stability and reproducibility of HVSR frequency peaks. A 35-day continuous HVSR monitoring performed in the suburbs of Algiers (Algeria) reveals that HVSR peaks are not always stable and reproducible both in frequency and amplitude. HVSR curves show a first peak, which varies from 0.9 to 1.8 Hz with amplitudes from 0.9 to 3.3, and a second peak from 5 to 7.7 Hz with amplitudes from 1.4 to 4. These results show that HVSR peak frequencies and amplitudes are highly sensitive to nearby anthropogenic sources.
Pure and Applied Geophysics, 2017
Bedrock depths in the Mitidja basin in general and in the Blida region in particular are still po... more Bedrock depths in the Mitidja basin in general and in the Blida region in particular are still poorly known despite, the existence of some relatively deep hydraulic boreholes that intersect only superficial alluvial formations. To assess the seismic risk of Blida town, knowledge of soil amplification requires the thickness and properties of sedimentary formations that cover the substratum. For the purposes of our study, the thicknesses obtained by the vertical electric soundings, carried out in the hydrogeological study of the basin, were combined with horizontal-to-vertical spectral ratio (HVSR) microtremor recordings. This combination made it possible to determine an empirical relationship between frequency and thickness specific to the Blida site area, which enabled the roof of the Miocene to be mapped and shows slight undulations with directions compatible with the tectonic constraints of the region. The boundaries between the low and high frequencies obtained by HVSR are well materialized, at south by Sidi El Kebir river, at west by Chiffa river and in the central part by a line of direction SE-NW corresponding to the old passage of Sidi El Kebir river. The presence of low frequencies attributed to the old alluvial deposits with significant thicknesses that originate just after Sidi El Kebir river confirms that the South Mitidjian contact is subvertical.
Arabian Journal of Geosciences, 2017
The Sablettes (Algiers) coastal reclaimed fringe region, located on the hanging wall of the Sahel... more The Sablettes (Algiers) coastal reclaimed fringe region, located on the hanging wall of the Sahel active fault, is subject to different types of geological hazard such as flood and tsunami, coastal uplift, earthquake, liquefaction, landslide , and site effects. In this present work, we used ambient vibration HVSR for imaging the bedrock. The thickness of the sedimentary column under the backfill layer is unknown, and the coastal reclaimed areas are prone to strong amplification of seismic waves. The determination of the depth of the metamorphic base allowed us to establish a mapping of the bedrock roof surface. The 3D representation of this surface enabled us to present models of tectonic structures in this basement (i.e., fault, fold). This analysis will make it possible to make better evaluation of the amplification after having determined the depth of the metamorphic basement exceeding 240 m, which is supposed to have velocities close to those of the seismological basement, as well as the thicknesses of the different layers surmounting it. Keywords Bedrock imaging. Ambient vibrations. HVSR. The Sablettes (Algiers) reclaimed area This article is part of the Topical Collection on Current Advances in Geology of North Africa
Arabian Journal of Geosciences, 2017
Ambient vibrations have been continuously recorded at Dar El Beida, about 20 km from Algiers (Alg... more Ambient vibrations have been continuously recorded at Dar El Beida, about 20 km from Algiers (Algeria). This data set allows determining that, in the low-frequency domain (<1 Hz), ambient vibration sources are mainly linked to Mediterranean Sea effects, while in the high-frequency domain, they are closely related to anthropogenic activity. Climatic conditions have an influence on the ambient vibration spectral amplitudes in the low-frequency domain, which is not the case in the high-frequency domain. The limit between the low-frequency and high-frequency domain, based on natural versus anthropogenic activity, is not clear cut and lies between 1.25 and 1.50 Hz. Variations of H/V peak amplitudes in the low-frequency domain are clearly linked to the climatic conditions. In the high-frequency domain, H/V peaks are not related to climatic conditions and cannot be clearly related to anthropogenic source changes.
Second International Conference on Engineering Geophysics, 2013
In order to development the land additional at Mohammedia site, situated northern Algeria, near t... more In order to development the land additional at Mohammedia site, situated northern Algeria, near the sea, and it is one part of the project shoreline development throughout the region of Algiers, geophysical data acquisition and processing from ambient vibration noise have been made to understand the ground vibrations in terms of frequency and amplification. We are also trying to estimate the thickness of boosting layers formed mainly by embankments sometimes overcoming quaternary alluvium.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
Arabian Journal of Geosciences
Arabian Journal of Geosciences, 2017
Seismological Research Letters, 2016
Pure and Applied Geophysics, 2016
Uploads
Papers by El Hadi Oubaiche