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We have kindly received the comments by Hamdache and Pelàez on our published paper (Hamidatou et al. 2019); This article will give us the opportunity to provide more explanation and clarifications on the methodology followed during our work. We find these comments and critiques helpful for our future works. However, most of them were generated from the misapprehension of the paper by the comment authors. These remarks were mainly based on (1) the misjudging of the seismic source zone model used in relation to the active faults in the study area, (2) suspecting that the probabilistic seismic hazard PGA values were wrongly quoted from their analyses in our work, and (3) the logic tree usage , for which we here provide further general clarifications. [ABSTRACT FROM AUTHOR]

We would like to make some comments on the paper by Hamidatou et al. (2019). Initially, these comments are motivated to reveal that, previous results on probabilistic seismic hazard analyses, some of them computed and published by our research group, are wrongly quoted in the paper by these authors. In our opinion, some other points are worthy of debate, mainly, but not only, the used seismic source zone model, the used logic-tree, and also the comparison of estimated values of peak ground horizontal acceleration (PGA) with previous results. [ABSTRACT FROM AUTHOR]

The Northern part of Algeria is considered to be the most active seismogenic area in the Western Mediterranean region. This area has a rich history of seismicity and had experienced many destructive earthquakes such as the Chlef (1954), El-Asnam (1980), Beni-Chograne (1994), Aïn-Temouchent (1999) and recently Boumerdes (2003) earthquakes. The earthquake of Aïn-Temouchent on December 22, 1999, was of magnitude 5.7, killed at least 28 people and made thousands of families homeless. Consequent damage was seen in all the structures located in a radius of 30 km. In the city of El-Maleh, located 12 km northeast of Aïn-Temouchent, the 'The National Bank Branch' of El-Maleh suffered moderate damage, but enough to justify questions about its safety. The project of rehabilitating this building required a broad analysis of its static and dynamic, past and present behaviors. The study reported in this paper was a necessary preliminary step toward the development of an optimal retrofit solution. [ABSTRACT FROM AUTHOR]

Seismic hazard in terms of spectral acceleration ( SA) has been estimated for the first time in northern Algeria. For this purpose, we have used the spatially-smoothed seismicity approach. The present paper is intended to be a continuation of previous work in which we have evaluated the seismic hazard in terms of peak ground acceleration ( PGA) using the same methodology. To perform these evaluations, four complete and Poissonian seismic models have been used. One of them considers earthquakes with magnitudes above M S 6.5 in the last 300 years, that is, the most energetic seismicity in the region. Firstly, seismic hazard maps in terms of SA, at periods of 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5 and 2.0 sec, with 39.3% and 10% probability of exceedance in 50 years, have been obtained. Therefore, uniform hazard spectra ( UHS) are computed and examined in detail for twelve of the most industrial and populated cities in northern Algeria. All the reported results in this study are for rock soil and 5% of damping. It is noteworthy that, in the seismic hazard maps as well as in the UHS plots, we observe maximum SA values in the central area of the Tell. The higher values are reached in the Chleff region (previously El Asnam), specifically around the location of the destructive earthquakes of September 9, 1954 ( M S 6.8), and October 10, 1980 ( M S 7.3). These maximum values, 0.4 g and 1.0 g, are associated with periods of about 0.2 and 0.3 sec for return periods of 100 and 475 years, respectively. [ABSTRACT FROM AUTHOR]

A single backscattering method is used to estimate coda quality factor functions (Qc) from coda-wave attenuation for the Algiers vicinity and eastern part of the Mitidja Basin. The frequency-dependent Qc relation is determined using a high-quality data set with good signal-to-noise ratios (SNR > 5) of 228 accelerogram waveforms of local earthquakes in the magnitude range 2.3–5.3, with focal depth varying from 1.3 to 31 km and epicentral distances less than 65 km. We studied the frequency and lapse time dependence of coda-wave attenuation through the variation of coda window length of 20, 30 and 35 s for seven frequency bands in the range of 1.5–24 Hz. The obtained average Qc increases with increasing coda window length, implying an increase in sampled depth. The Qc of horizontal components (N and E) are slightly lower than the Qc of the vertical component (Z). The obtained low values of Qc and high values of frequency-dependent parameter n indicate that the penetration depth that consists of the crust and part of the upper mantle beneath the Algiers region is seismically active with a high level of heterogeneity. The average frequency-dependent Qc values in the three directions are QcZ = (69.76 ± 2.98)f(0.82 ± 0.01), QcN = (60.2 ± 4.86)f(0.88 ± 0.03) and QcE = (59.63 ± 5.07)f(0.88 ± 0.03) with a coda window length of 20 s in which the penetration depth is 56.2 km and the covered area is 8141 km2. [ABSTRACT FROM AUTHOR]

Statistical tests have been used to adjust the Zemmouri seismic data using a distribution function. The Pareto law has been used and the probabilities of various expected earthquakes were computed. A mathematical expression giving the quantiles was established. The extreme values limiting law confirmed the accuracy of the adjustment method. Using the moment magnitude scale, a probabilistic model was made to predict the occurrences of strong earthquakes. The seismic structure has been characterized by the slope of the recurrence plot γ, fractal dimension D, concentration parameter Ksr, Hurst exponents Hr and Ht. The values of D, γ, Ksr, Hr, and Ht diminished many months before the principal seismic shock ( M = 6.9) of the studied seismoactive zone has occurred. Three stages of the deformation of the geophysical medium are manifested in the variation of the coefficient G% of the clustering of minor seismic events. [ABSTRACT FROM AUTHOR]

The aim of this study is the comparison between the fundamental periods identified experimentally and those calculated using the formulas given in the Algerian Seismic Code (RPA 99) for vulnerability assessment and for experimental data collection of selected sample of old buildings. The results obtained for vulnerability assessment will then be extrapolated to buildings of the same typology built during the 1949 to 1954 period in the northern part of Algeria. From 1949 to 1954, the reinforced concrete constructions in Algeria were built before the first generation of the Algerian Seismic Code. These buildings being old are certainly weakened by the occupancy activities and seismic event loads. Hence, the evaluation of their vulnerability with respect to the regional seismic hazard requires the knowledge of their structure on a site capacity. The empirical formulas to calculate the fundamental period of a building are based on the Algerian Earthquake Code (RPA 99) .These formulas consider only the geometrical dimension (length, width and height) and the structural design of the buildings. The fundamental periods of vibration of twenty-two buildings, located in Algiers, calculated using the empirical formulas given in the RPA 99 are lower than those identified experimentally. A question then rises, do these tested buildings present any damage or not? As five of these buildings were tested before the 21 May 2003 earthquake, the experimental testing highlighted a decrease in the fundamental frequency which means that these buildings are damaged. Hence, for vulnerability assessment, the empirical formulas given in the Algerian Seismic Code (RPA 99) may not be appropriate for vulnerability assessment of the old buildings built during the 1949 to 1954 period. [ABSTRACT FROM AUTHOR]

This study examines distinctive features of ground motion parameters in northern Algeria. An initial computation of seismic hazard in terms of horizontal peak ground acceleration (PGA) and spectral acceleration (SA) at different periods, damped at 5%, is carried out for three different types of soils (rock, stiff soils and soft soils) for return periods of 100 and 475 years. In addition, uniform hazard spectra (UHS) are computed for these two return periods at several locations in the region. Then, the UHS computed for different soil types are proposed as a starting point to define elastic design spectra for building-code purposes. We have used the well-known Newmark-Hall approach. As proposed in the most recent International Building Codes, the SA (0.2 s) value is used to establish the spectral region for lower periods (region controlled by acceleration), whereas the SA (1.0 s) value is used to establish the spectral region for intermediate periods (region controlled by velocity). We also obtained important relations, dependent on site condition, between SA (0.2 s), SA (1.0 s) or SA values, and the PGA, for both return periods of 100 and 475 years. Other relationships between PGA or SA values have also been derived for return periods of 100 and 475 years, in this case independent of site condition. [ABSTRACT FROM AUTHOR]