Boumerdes Earthquake Research Articles

Response spectra of earthquakes using ARMA model

This study is concerned with calculating hysteretic energy using ARMA coefficient models. We know that: For any random time series we can write a model of ARMA(p,q) detailed by Box and Jenkins [2]. Any movement generates energy, regardless of its form or type, negative or positive, so how do we deal with it or reduce its danger? This is possible through ARMA models that have proven their efficiency through several procedures such as earthquakes and accelerometer time series that are generated from random models in the time domain or frequency domain. Extensive reviews of time series process models for acceleration in the frequency and times domain have been presented by [1], [12], and [4]. A number of papers have reported on ARMA models. ARMA models are discussed in detail by Box and Jenkins [4]. Here we generally found the hysteretic energy NH in terms of the ARMA(2,1) coefficients, but the ARMA(2,1) model can be considered the most appropriate in this case for the regions of northern Algeria, from which we took the Boumerdes earthquake. When taking the AIC RITERIA criterion, we found that it is in fact ARMA. (2,1) which is what we studied The use of mathematical relationships, including some results of nodal integration, such as relationship [7] , which conforms to the definition of a stationary time series, which is that the mean and standard deviation are constant.

Dinamička analiza lučne brane

Introduction/purpose: The dynamic analysis of a seismic response of a concrete vault dam is a complex problem in which the representation of the behavior of the material requires some form of a nonlinear model, especially if the concrete is subjected to a significant stress load of the ground. In the case of large movements of the latter, large cracks may form in some areas of the dam, especially at the base of the dam and near sudden changes in geometry. Methods: This analysis was based on a numerical simulation of the dynamic effect. This work was carried out using the finite element method with the ANSYS 12.1 program. The dam was modelled in two dimensions. Four types of analysis were performed: static analysis, modal analysis, seismic analysis under excitation of two accelerograms (Asnam 1980 and Boumerdes 2003), and spectral analysis. Results: This analysis showed the vulnerability of the Brezina dam to the Boumerdes earthquake with high stresses at the base of the structure. Conclusions: Based on this study, it was concluded that if the Brezina dam suffers an earthquake of a greater intensity than that of Boumerdes, this will cause structural damage and cracks that will compromise the dam's watertightness as well as its durability.

Comparative Study of the Non-Linear Dynamic Behaviour of Different Seismic Isolation Systems

To mitigate the effect of earthquake on the structure, the base isolation technique is the best alternative as a seismic protection system. In this research, a two-degree-of-freedom (2DOF) equivalent model is modelled based on a real eight-level reinforced concrete structure damaged by the Boumerdes earthquake in 2003 is presented. The basic isolation systems considered are four models namely: the first system is a high damping isolator (HDBR), the second system is the friction pendulum isolator (FPS). The third model of the base isolation system is a non-linear model with two horizontal and rotational stiffness springs (SHRS), and finally the last model presents a bilinear spring (SB). The isolators are designed according to the UBC-97 code. Earthquake recordings from Dar-El-Beida of the 2003 Boumerdes earthquake were used as seismic load. A dynamic analysis of the comparative temporal responses of the structure was performed by comparing its dynamic behaviour with that of the fixed base structure. The results obtained reveal a reduction in base shear, stage drift and stage acceleration and an increase in displacement and time period for the structure isolated at the base. The results are presented in tables and graphs.

Fault plane picking from focal mechanisms in reverse faulting stress: Application to the Mw6.9 Boumerdes (Algeria) earthquake sequence

Identification of the fault plane from two nodal planes of the focal mechanism is, in general, ambiguous. This problem is commonly solved using other constraints provided by tectonic, geological or seismic studies. In this paper, we evaluate the probability of identifying the fault plane using knowledge of stress field. We employ two alternative methods: (1) the slip angle method (SA), and (2) the highest instability method (IS). First, the efficiency of the methods was tested on synthetic data consisting of focal mechanisms compatible with a reverse stress regime. The tests revealed that the fraction of faults correctly picked by the IS method is higher than that of the SA method, particularly for large noise values. Second, the methods were applied to the aftershocks of the Boumerdes (Algeria) earthquake of May 21, 2003. This application showed that when taking into account the focal solutions for which the fault planes are determined using the IS method with a high probability, we observe consistency between the selected faults and the tectonics of the study area.

The Review of Algerian Building Seismic Code(RPA) in Seven Points Compared to American and European Codes

The first Algerian seismic code named "Règles Parasismiques Algériennes" (RPA, 1981) was established after the terrible 1980 Chlef earthquake (M 7.3), which caused a great disaster. Since this catastrophic event a continually reviewed versions, in particular after the 2003 Boumerdes earthquake (M 6.8) which caused an immense hazardous loss in human lives and construction damages (2000 seath) persons killed). This harmful event urged on to a serious review leading to the last and present version of such standard earthquake (RPA, 2003) with fundamental modifications concerning many important fields. The points revealed in the present review research study are the classification of sites, design methods, design spectrum, ductility concept, behavior factor, self-steady structures and dual systems (frames and walls). The outcome of the study here in is summarized as a brief review that could be a contribution to enrich the Algerian seismic regulation (RPA) with a focus on these seven important points selected as they seem to present some anomalies or deficiencies detected and treated on the basis of two main parameters. Firstly, we consider the damage observed after the 2003 Boumerdes earthquake; later in the second step, a comparison is made with other codes practiced over the world alike the European EC8 or the American Uniform Building Code, 1994 (UBC 94) or the 2000 NEHRP Provisions.

Nonlinear Deterministic Study of Seismic Microzoning of a City in North of Algeria

This paper presents also an overview of seismic microzonation studies of the city of Mohammadia-Algiers, which are important for a detailed ground movement modeling of urban cities. According to the seismic history of the city, one extraordinary earthquake event has been taken into consideration is Boumerdes earthquake (Algeria, May 21, 2003, magnitude Mw=6.5), that caused a huge damage. Thereby, the variability prediction of the seismic ground movement in a given built-up area, it is considered as an effective tool for planning appropriate urban development and understanding both seismic risk and damage pattern, caused by a strong movement event. We note that the shaking level is mainly described in terms of both maximum ground acceleration and visualized amplification by using response spectra. The study is carried out in two steps: - a detailed mapping of the geology and geotechnical properties of the area - numerical modeling of expected ground motions during earthquakes. A qualitative microzonation of the Mohammadia-Algiers city is presented, and it is discussed by comparing it to the historically reported damage of the 2003 Boumerdes earthquake. Finally, this study deals with the seismic microzonation map development, based on a SIG geological model.

Evolution of Soil Settlements under a Rockfill Dam Based on Potential Earthquake Harmfulness (PEH) 'Case of Boumerdes Earthquake, Algeria 2003'

Earthquakes are part of the natural cataclysms that are responsible for the destruction of entire cities, causing the deaths of millions of people and often have disastrous economic consequences. Therefore, it is important to consider measures of the intensity of seismic movement in risk analysis (Potential Earthquake Harmfulness ‘PEH’). The purpose of this study is to model the mass of soil under a rockfill embankment in order to evaluate the soil settlement under the effect of an earthquake of Boumerdes (Algeria 2003) using “plaxis” finite element code. The PEH characterizes in our study the Aria intensity IA(t) and the cumulative absolute velocity CAV(t), on the one hand, and on the other hand, empirical correlations between the indicators of harmfulness (PEH) and the settlements under the base of the dike. The correlations thus obtained (Uy-PEH) are slightly influenced by the gravitational loads and a tighter dispersion of the point cloud is observed on the correlations (Uy-IA).

Numerical Analysis of Keddara Dam under Seismic Motion

The Boumerdes earthquake of May 21, 2003 in Algeria, which widely felt within a radius of ~ 400 km, caused damage in five provinces. Numerous structures have been devastated, others suffered of damages. Keddara rockfill dam which is situated approximately at 20 km from the epicentre was strongly shaken during this seismic event and can undergo significant deformations. In this study, numerical analysis of Keddara rockfill dam under Boumerdes earthquake is performed. It is mainly focus on the seismic amplification at different level of the dam under the main shock with dominant frequency close to the natural frequency of the dam. The low coherence between the input and the structural output indicates the need of nonlinear analysis of the dam under the spatial variation in excitation. Furthermore, the effect of plasticity on the seismic response is investigated by using maximum acceleration which is one of the most important properties selected. The analysis of the dam under stochastic non-uniform excitation is conducted using a 2-D finite difference modeling by using the software Fast Lagrangian Analysis of Continua (FLAC). The final results obtained after successive analyses on the dam configuration incorporating the nonlinear soil properties are presented.

Effect of the uncertainty on the formulated seismic behavior of RC buildings to a given earthquake

This paper presents a stochastic analysis of expressions linking the reinforced concrete (RC) buildings maximum displacements to their natural period and the epicentral distances. Where, low- and medium-rise reinforced concrete buildings, are tested under the effect of records collected during the Boumerdes earthquake (Algeria, May 21st, 2003) at different epicentral distances. First, the expressions linking building maximum displacement and interstory drift to the building natural period and epicentral distance are derived. Then, using Monte Carlo simulation, the effect of the uncertainty of the chosen parameters on the confidence intervals of the lateral displacement and interstory drift statistics is studied, where the natural period and the epicentral distance are considered as random variables with a log-normal distribution. The findings denote that the derived expressions are less influenced by fundamental period uncertainty than the that of the epicentral distance. A good accuracy in the established formulations is reflected by the small width of the confidence intervals of the both analyzed responses.

Analysis the dynamic response of earth dam in free vibration and forced by introducing the effect of the interaction dam foundation

The present study concerns the analysis of the dynamic response of earth dam, in free and forced vibration (under the effect of earthquake) using the finite element method. The analysis is carried out at the end of dam construction without filling. The behavior of the dam materials and the foundation is linear elastic. In free vibration, to better understand the effect of the dam foundation interaction, we will take into account different site conditions and see their influence on the free vibration characteristics of the dam. In forced vibration, to study the seismic response of the dam, the system is subjected to the acceleration of the Boumerdes earthquake of May 21, 2003 recorded at the station n ° 2 of the dam of Kaddara in the base, with a parametric study taking into account the influence of the main parameters such as the mechanical properties of the soil: rigidity, density.

Analysis the dynamic response of earth dam in free vibration and forced by introducing the effect of the interaction dam foundation

The present study concerns the analysis of the dynamic response of earth dam, in free and forced vibration (under the effect of earthquake) using the finite element method. The analysis is carried out at the end of dam construction without filling. The behavior of the dam materials and the foundation is linear elastic. In free vibration, to better understand the effect of the dam foundation interaction, we will take into account different site conditions and see their influence on the free vibration characteristics of the dam. In forced vibration, to study the seismic response of the dam, the system is subjected to the acceleration of the Boumerdes earthquake of May 21, 2003 recorded at the station n ° 2 of the dam of Kaddara in the base, with a parametric study taking into account the influence of the main parameters such as the mechanical properties of the soil: rigidity, density.

The large Algerian earthquakes (267 A.D.-2017)

In northern Algeria, large earthquakes occurred in the past as the El Asnam earthquake of October 10th, 1980 (Ms:7.3), one of the strongest event ever recorded in the western Mediterranean region. There were located mostly in the Tellian Atlas, some of them off the coastline as the Algiers (1365), Oran (1790), Djidjelli (1856) earthquakes or the last Boumerdes earthquake (2003). On land, no strong earthquakes have been recorded in the High plateaus or along the Saharan Atlas. From a synthesis of seismological or geodynamical studies carried out on the Algerian seismicity, we conclude that these main events along the African-Eurasiatic plate boundary are representative of the actual deformation pattern of the different geological domains of northern Algeria. They are generated mainly by reverse faults or strike slip faults in relation with the NW-SE to NNW-SSE stress regime (σ 1 striking N330°- N350°) inherited from the oblique convergence process between the two main plates in the western Mediterranean region. They are in general superficial located in the upper part of the crust (no more than 20 Km). Important earthquakes do not occur very often in Algeria in comparison with other seismic regions of the world. Their return period are estimated in some regions to be of many hundred of years. Large earthquakes still cause important damage to cities and villages, sometimes with the loss of thousand of citizens.

Full Aftershock Sequence of the M w 6.9 2003 Boumerdes Earthquake, Algeria: Space–Time Distribution, Local Tomography and Seismotectonic Implications

We present a detailed analysis of the aftershocks of the May 21, 2003 Boumerdes earthquake (M w = 6.9) recorded by 35 seismological stations and 2 OBS deployed in the epicentral area. This network recorded the aftershock activity for about 1 year and resulted in locating about 2500 events. The five main aftershocks (4.7 <M <5.8) display thrust faulting consistent with the main shock, except for the second event (M5.8, 29/05/2003) which depicts a strike-slip focal solution at the western tip of the rupture zone. Most aftershocks are clustered near the main rupture plane, in the footwall or at the westernmost tip of the 2003 Boumerdes rupture area. Many aftershocks last over the whole seismic crisis ahead (north) of the main rupture zone, forming a diffuse, low-angle surface within the footwall where the coseismic static stress change is predicted to increase. At the SW tip of the rupture, short-lived clusters locate at intersections of faults near the contact between the inner (Kabylia) and outer (Tell) zones. The tomographic inversion depicts high-velocity P- and S-wave anomalies coinciding with Miocene magmatic intrusive bodies in the upper crust, partially hidden by surrounding basins. The area of the main shock is associated with a large low-velocity body subdivided into sub-domains, including Neogene basins on land and offshore. Our results support a rupture model strongly controlled by geological inhomogeneities and extending as ramp–flat–ramp systems upward, favoring heterogeneous slip and segmentation in the fault plane with strong afterslip toward the surface. The diffuse aftershock activity in the footwall evidences an inherited discontinuity at mid-crustal depth that we interpret as the contact of Kabylian and African (Tethyan) continental crusts that were stacked during the Upper Miocene collision.

A structural scheme proposal derived from geophysical data in the epicentral area of the Boumerdes (Algeria) earthquake of May 21, 2003

In this study, we processed and interpreted gravity and aeromagnetic data of the epicentral area of the Boumerdes earthquake (May 21, 2003). The joint interpretation of both data allowed the development of a structural scheme that shows the basement undulations offshore and onshore. The shape of the eastern part of the Mitidja Basin is better defined; its northern edge is represented by a large “sub-circular” uplifted basement located offshore. The rise of this basement indicates that this basin does not extend towards the sea. At the eastern part of the study area, aeromagnetic data have revealed that the Sid-Ali-Bounab basement is individualized in a “sub-circular” shape, while the Dellys basement, located in the NE part, is elongated in the NE-SW direction and extends offshore. The aeromagnetic data also highlighted two EW basement uplifts which divide Isser depression into three parts. The northern part of this depression extends offshore. The southernmost uplift is an extension of the Thenia Fault (TF), suggesting the continuity of this fault to the east. It is important to note that the active Reghaia Fault (RF), which runs through the Boudouaou and Reghaia urban centers, is bounded by two faults suggesting that its length does not exceed 12 km. Moreover, alluvial terraces observed west of the active Zemmouri Fault (ZF) are in agreement with the reverse component of this fault.

Dissipation’s Capacity Study of Lead–Rubber Bearing System in Seismic Steel Structures Design

The integrity and serviceability of the steel multi-storey buildings structures against natural hazard such as earthquake were a challenge for structural engineers and researches. The major concern in the design of these structures is to have enough lateral stability to resist wind and seismic forces. There are different ways to limit the lateral drift. Among these ways, there are base-isolation systems which became one of the challenging subjects for researchers from previous years. This paper concerns an examination of the seismic response of multi-storey steel building fitted with lead–rubber base-isolation system using a 3D numerical investigation. Fast nonlinear time history analysis considering Boumerdes earthquake (Algeria, May 2003) is achieved for analysing and carrying out using commercial software. Comparisons between fixed base, bearing base-isolated and braced structures are shown in a tabulated and graphical format. The results of the diverse alternatives investigated to evaluate the structural response with and without this device of dissipation energy thus obtained were discussed. The conclusions showed the good potential of the lead–rubber isolators. This system may improve the dissipative capacities of the structure without increasing its rigidity in a significant way, which contributes to optimize the quantity of steel required for its overall stability.

Pre-seismic anomalies in remotely sensed land surface temperature measurements: The case study of 2003 Boumerdes earthquake

Detection of thermal anomaly prior to earthquake events has been widely confirmed by researchers over the past decade. One of the popular approaches for anomaly detection is the Robust Satellite Approach (RST). In this paper, we use this method on a collection of six years of MODIS satellite data, representingland surface temperature (LST) images to predict 21st May 2003 Boumerdes Algeria earthquake. The thermal anomalies results were compared with the ambient temperature variation measured in three meteorological stations of Algerian National Office of Meteorology (ONM) (DELLYS-AFIR, TIZI-OUZOU, and DAR-EL-BEIDA). The results confirm the importance of RST as an approach highly effective for monitoring the earthquakes.

Ambient seismic vibration analysis and ground characterization in the vicinity of Algiers seismic zone

The Dar El Beida area, situated in the Mitidja basin, in the north central Tellian Atlas is characterized by its Plio-Quaternary sediments. The site effect analysis in this zone surrounding Algiers city is very important. The soil is constituted from recent soft sediments capable of amplifying seismic motion. Indeed, the analysis thanks to the ratio H/V ambient vibration method confirms these assumptions. An electric resistivity tomography strengthened the results obtained from ambient vibration for site characterization. This demonstrates once again the more or less homogeneous character of formations in this area. However, strongly amplifying its sediments largely explains the seismic acceleration of 0.52 g recorded following the 2003 Boumerdes earthquake.

Slope topography-induced spatial variation correlation with observed building damages in Corso during the May 21, 2003, M w 6.8, Boumerdes earthquake (Algeria)

During the May 21, 2003 M w 6.8 Boumerdes earthquake, in the “Cite des 102 Logements” built on a hilltop, in Corso, heavy damages were observed: near the crest, a four-story RC building collapsed while others experienced severe structural damage and far from the crest, slight damage was observed. In the present paper, we perform a 2D slope topography seismic analysis and investigate its effects on the response at the plateau as well as the correlation with the observed damage distribution. A site-specific seismic scenario is used involving seismological, geological, and geotechnical data. 2D finite element numerical seismic study of the idealized Corso site subjected to vertical SV wave propagation is carried out by the universal code FLUSH. The results highlighted the main factors that explain the causes of block collapse, located 8-26 m far from the crest. These are as follows: (i) a significant spatial variation of ground response along the plateau due to the topographic effect, (ii) this spatial variation presents high loss of coherence, (iii) the seismic ground responses (PGA and response spectra) reach their maxima, and (iv) the fundamental frequency of the collapsed blocks coincides with the frequency content of the topographic component. For distances far from the crest where slight damages were observed, the topographic contribution is found negligible. On the basis of these results, it is important to take into account the topographic effect and the induced spatial variability in the seismic design of structures sited near the crest of slope.

Failure analysis of an apartment building surmounted by a RC water tank – Case study

The structure that is the subject of interest in this work is an apartment building in Algiers surmounted by a reinforced concrete (RC) water tank with a container capacity of 1000m3. Since its entry into service in 1962, this structure was subjected to several earthquakes (El Asnam 1980, Constantine 1985, Oued Djer 1988) without being disturbed. However, the Boumerdes earthquake of May 21st, 2003 was severely damaging to this structure. It was downgraded after a study conducted by the Construction Control Agency because the central core had undergone serious damage. As for the walls, columns, and beams, they were not affected. Through this paper, the reasons for the failure of this RC structure (building-reservoir) will be explored and the repair measures carried out. Investigation work on site, supplemented by seismic analysis after finite element modelling, will be described. The technique of jacketing, used as repair solution to improve the strength of the studied structure, is presented at the end of this paper.

Seismic energy dissipation study of linear fluid viscous dampers in steel structure design

Energy dissipation systems in civil engineering structures are sought when it comes to removing unwanted energy such as earthquake and wind. Among these systems, there is combination of structural steel frames with passive energy dissipation provided by Fluid Viscous Dampers (FVD). This device is increasingly used to provide better seismic protection for existing as well as new buildings and bridges. A 3D numerical investigation is done considering the seismic response of a twelve-storey steel building moment frame with diagonal FVD that have linear force versus velocity behaviour. Nonlinear time history, which is being calculated by Fast nonlinear analysis (FNA), of Boumerdes earthquake (Algeria, May 2003) is considered for the analysis and carried out using the SAP2000 software and comparisons between unbraced, braced and damped structure are shown in a tabulated and graphical format. The results of the various systems are studied to compare the structural response with and without this device of the energy dissipation thus obtained. The conclusions showed the formidable potential of the FVD to improve the dissipative capacities of the structure without increasing its rigidity. It is contributing significantly to reduce the quantity of steel necessary for its general stability.