Homogeneous Earthquake Catalogue Research Articles

Probabilistic Assessment of Seismic Hazard for Uttarakhand State of India

Abstract Uttarakhand state of India, being located in the seismically active Himalayan mountain range, is highly prone to seismic hazards. This study presents assessment of seismic hazard of Uttarakhand through probabilistic approach. For conducting this study, a homogenous earthquake catalogue for moment magnitude during the period 1953 - 2020 with magnitude range of 2.0 - 6.9 consisting of 522 events was used. Various geological structures viz. folds, faults and lineament as well as thrust, have been identified in the associated regions. The state was divided into several grid points and the seismic hazard was evaluated for each of the grid points through probabilistic method. Finally, based on the analysis results, bedrock level hazard maps were developed for the state for contingency level earthquake (CLE) and maximum credible earthquake (MCE). The estimated peak ground acceleration (PGA) of the state is in the range of 0.16g-0.52g for CLE and the PGA varies for 0.20g-0.61g for MCE level earthquake. Main Central Thrust (MCT), Sunder Nagar fault and Ropar fault were observed to be more hazardous in the northern region of the state.

An updated homogeneous earthquake catalogue and earthquake recurrence parameters of Maharashtra state, an Indian stable continental region

An updated homogeneous earthquake catalogue and earthquake recurrence parameters of Maharashtra state, an Indian stable continental region

Creating a homogenized earthquake catalog for Algeria and mapping the main seismic parameters using a geographic information system

A homogeneous earthquake catalog is an essential instrument to study earthquake occurrence patterns, employing diverse engineering applications. In this paper, we describe a series of compilation and processing steps to compile an updated earthquake catalog for Algeria, a North African country with relatively high seismic activity. The procedure consisted of several steps. First, a range of reliable catalogs were considered; second, the data was integrated and refined; third, magnitudes are homogenized from different kinds of magnitudes into moment magnitude (Mw); declustering is then performed; and, finally, the magnitude-year completeness was estimated. The resulting Algeria catalog is bounded by the geographical limits (19°–38.5° N and 9.5° W − 12.5° E), and covers the 1960–2020 period. It includes 4021 seismic events, reported up to Mw 7.1. We also calculate a set of seismic parameters, namely Mmax and b-value, and mapped them using a geographic information system. Thus, the territory is divided into cells based on different grids to conduct the analysis. The results of the seismic parameters mapping are discussed, highlighting significant details. Several cells presented a Mmax between 6.0 and 7.1. Regarding the b-value, two regions (Oran and Constantine) presented a high b-value, implying low-stress areas, and three regions (Algiers, Batna, and Chlef) a low b-value (0.65− 0.85), suggesting high-stress areas. Finally, we suggest some recommendations for future seismic hazard assessment studies.

Distribution of b‐values in Indo‐Burma Ranges, northeast India: Implications to structural heterogeneities and style of faulting

The spatial distribution of the b‐value has been determined using a homogeneous earthquake catalogue from 1964 to 2018 to examine the characteristics of structural heterogeneities and their bearing on the style of faulting in the Indo‐Burma region of Northeastern India. The study region is associated with an uneven distribution of structural heterogeneities and demonstrates the mixed type of faulting, nature where the majority of earthquakes resulted mainly by thrust and strike‐slip fault. Our critical analysis demonstrates that the existence of two prominent zones is associated with high b‐values and low b‐values where the mixed type of faulting resulted in the genesis of seismicity in the study area. The high b‐values in the study area contain a large number of smaller earthquakes whilst the low b‐values comprise a smaller number of larger earthquakes distributed along with the Naga‐Disang Thrust, Kabaw Fault, and Sagaing fault systems. A close comparison between b‐values and different faulting styles reveals that the area containing a low b‐value suggests stronger seismogenic zones, where an accumulation of strain energy leads to the genesis of seismicity by thrust faulting with slight slip component whilst Indo‐Burma Ranges regions connected with b‐values (0.5–0.9) demonstrate strike‐slip to the normal mode of faulting, indicating relatively weak seismogenic zones where tensional forces are prevalent. The depth sections illustrate that lower b‐values for the upper part of the subducting slab correspond to more stress generated by tectonics compared to that of the lower part, and interestingly the deeper part of the subducting Indian slab is coupled with conspicuously very high‐b values, suggesting the weakening of the Indian subducting slab through dehydration.

A homogeneous earthquake catalogue for Turkey

Abstract. A new homogenized earthquake catalogue for Turkey is compiled for the period 1900–2018. The earthquake parameters are obtained from the Bulletin of International Seismological Centre that was fully updated in 2020. New conversion equations between moment magnitude and the other scales (md, ML, mb, Ms, and M) are determined using the general orthogonal regression method to build up a homogeneous catalogue, which is the essential database for seismic hazard studies. The 95 % confidence intervals are estimated using the bootstrap method with 1000 samples. The equivalent moment magnitudes (Mw*) for the entire catalogue are calculated using the magnitude relations to homogenize the catalogue. The magnitude of completeness is 2.7 Mw*. The final catalogue is not declustered or truncated using a threshold magnitude in order to be a widely usable catalogue. It contains not only Mw* but also the average and median of the observed magnitudes for each event. Contrary to the limited earthquake parameters in the previous catalogues for Turkey, the 45 parameters of ∼378 000 events are presented in this study.

Analysis of Basic Hazard Parameters Before and After the February 6, 2017 Ayvacik Earthquake (Mw=5.4)

Kuzeybatı Ege bölgesinin en karmaşık tektonik unsurlarını barındıran Biga Yarımadası oldukça yoğun bir dep-remsellik gösterir. Bu yarımada ve yakın çevresi için farklı dönemlerde meydana gelen orta ve büyük depremlerin deprem tehlikesi analizi, çalışmanın temelini oluşturmaktadır. Temel deprem parametreleri olarak da bilinen a ve b-değerleri bu çalışmanın veri tabanı olan aletsel dönem deprem kataloğundaki M>2 için belirlenmiş ve değerlendi-rilmiştir. Bu çalışmada, ÇOMÜ) ve KRDAE tarafından işletilen deprem istasyonları ve buna bağlı yüksek kaliteli faz okumaları sonucuna dayalı ortak bir deprem kataloğu kullanılmıştır. Ayvacık başta olmak üzere ve yakın çevresinde 6 Şubat 2017’de meydana gelen Mw=5.4 büyüklüğündeki deprem ile başlayan ve süreklilik gösteren deprem sonrası aktivitenin Tuzla deformasyon zonu çevresinde yaklaşık 25x10 km’lik bir alanda kümelendiği gözlenmiştir. Bu deprem öncesi ve sonrası yerel tektonik yapılar ve gerilme durumları ile ilişkilendirilebilecek başta b-değeri olmak üzere olasılıksal parametreler de değerlendirilmiştir. Kısa ve uzun dönemde bu parametrelerin ana deprem öncesi ve sonrası azalım ve artış eğilimleri yerel ve bölgesel hâkim gerilmelerin yanında üst kabuktaki heterojenite ve jeotermal kaynaklar da göz önünde bulundurularak sismisite ve sismotektonik yapıya katkısı ve ilişkisi uzaysal ve zamansal olarak incelenmiştir. Saroz-Ayvacık-Edremit doğrultusunda alansal olarak deprem verisi yoğunluğu dikkate alındığında b-değerlerinin gerilmelerle ters orantılı olarak deprem öncesi artışı ve akabin-de de bu davranış azalımı 2014 ve 2017 depremleri ile kendisini göstermiştir.

Integration of local soil effect into the assessment of seismic hazard at the Kharga Oasis, Western Desert, Egypt

The effect of local soil is integrated into the assessment of seismic hazard at the Kharga Oasis, Western Desert, Egypt. The work is done by adopting the probabilistic approach of seismic hazard assessment and the site response analysis. The probabilistic approach was utilized based on a homogenous earthquake catalogue, a reasonable seismic source model, and selective ground-motion prediction equations. The site response analysis is performed to describe the interaction between ground motion time series that are well-matched with the results of the probabilistic analysis and the dynamic soil properties defined from the seismic survey. The outputs are presented in terms of the site-specific seismic hazard maps which includes the amplification maps and maps for the expected values of the ground motion at the surface. The amplification maps show that the northern part of the area has the lowest amplification while the middle part of the area has the highest amplification. The maps for peak ground acceleration and spectral acceleration for the return periods of 475 years show that the maximum expected peak ground acceleration for this return period is 100.6 cm/s2. It has the values of 135 cm/s2 at 0.1 s spectral acceleration.

Generating a seismogenic source zone model for the Pyrenees: A GIS-assisted triclustering approach

Seismogenic source zone models, including the delineation and the characterization, still have a role to play in seismic hazard calculations, particularly in regions with moderate or low to moderate seismicity. Seismic source zones establish areas with common tectonic and seismic characteristics, described by a unique magnitude–frequency distribution. Their definition can be addressed from different views. Traditionally, the source zones have been geographically outlined from seismotectonic, geological structures, and earthquake catalogs. Geographic information systems (GIS) can be of great help in their definition, as they deal rigorously and less ambiguously with the available geographical data. Moreover, novel computer science approaches are now being employed in their definition. The Pyrenees mountain range – in southwest Europe – is located in a region characterized by low to moderate seismicity. In this study, a method based purely on seismic catalogs, managed with a GIS and a triclustering algorithm, were used to delineate seismogenic zones in the Pyrenees. Based on an updated, reviewed, declustered, extensive, and homogeneous earthquake catalog (including detailed information about each event such as date and time, hypocentral location, and size), a triclustering algorithm has been applied to generate the seismogenic zones. The method seeks seismicity patterns in a quasi-objective manner following an initial assessment as to the best suited seismic parameters. The eight zones identified as part of this study are represented on maps to be analyzed, being the zone covered by the Arudy–Arette region to Bagnères de Bigorre as the one with the highest seismic hazard potential.

A unified moment magnitude earthquake catalog for Northeast India

Earthquake-related studies on seismicity and seismic hazard assessment need a homogenous earthquake catalog for the region studied. A homogenous earthquake catalog for Northeast India region was compiled using derived regional and global empirical relationships between different magnitudes and moment magnitude based on an improved error-corrected methodology suggested in the recent literature. To convert smaller magnitude earthquakes, global empirical equations were derived and used. A procedure is suggested to change different magnitudes into moment magnitude. A homogenous earthquake catalog of 9845 events was compiled for the time period 1897–2012. Entire magnitude range (EMR) was found to be the most reasonable method for estimating magnitude of completeness. Derived local and global empirical equations are useful for every seismic hazard or seismicity study. A complete and consistent homogenized earthquake catalog prepared in this study could provide good data for studying earthquake distribution in Northeast India. By carefully converting these original magnitudes into homogenized Mw magnitudes, an obstacle is removed for the consistent assessment of seismic hazards in Northeast India.

Updating a probabilistic seismic hazard model for Sultanate of Oman

Earthquake Monitoring Center (EMC) at Sultan Qaboos University (SQU) initiated evaluating the seismic hazard in the Sultanate of Oman in 2009. EMC has produced the first probabilistic and deterministic seismic hazard maps for Oman in 2012 and 2013, respectively. In the current study, the probabilistic seismic hazard assessment (PSHA) is revisited to provide an updated assessment of the seismic actions on the Sultanate. The present study has several advantages over its predecessor: using an updated homogeneous earthquake catalogue, recently developed seismic source model; inclusion of epistemic uncertainties for the source models, recurrence parameters, maximum magnitude, and more recent and applicable ground-motion prediction equations (GMPEs). Epistemic uncertainties were treated using a combination of the best available databases within a properly weighted logic tree framework. Seismic hazard maps in terms of horizontal peak ground acceleration (PGA) and 5% damped spectral accelerations (SA) at the bedrock conditions (VS = 760 m/s) for 475- and 2475-year return periods were generated using the classical Cornell-McGuire approach. Additionally, uniform hazard spectra (UHS) for the important population centers are provided. The results show higher values at the northern parts of the country compared to the hazard values obtained in the previous study.

Seismicity and seismic hazard parameters in and around Pakistan

Pakistan holds a key position within the Indian–Eurasian collision zone and is a highly earthquake-prone country of South Asia. Besides the devastating earthquakes of Quetta 1935, Makran 1945 and Pattan 1974, the earthquakes that happened in Bhuj 2001, Kashmir 2005 and Hindu Kush 2015 are three typical examples of the new millennium. In this study, the earthquake probability and the return period for magnitude recurrence hazard have been analysed using a magnitude homogenous earthquake catalogue. In Gumbel’s theory of extreme values, the Gumbel III distribution has a vital role to play as far as seismic hazard analysis of any regional seismicity is concerned. The Gumbel III distribution is used here to estimate the upper bound magnitude (ω value) and other earthquake hazard parameters in and around Pakistan. This method is applied to the whole of Pakistan (23° N–39° N; 59° E–80° E) and shallow (0–70 km) and intermediate (70–300 km) depth earthquakes in the Hindu Kush region across the Afghanistan–Pakistan border over the period 1930–2007. From the entire Pakistan dataset, the ω value is estimated as 8.12 (± 0.59). Furthermore, intermediate earthquakes in Hindu Kush have a ω value of 8.15 (± 0.56) compared with 7.08 (± 0.92) for the shallow earthquakes in the Hindu Kush. From probabilistic analysis of a spatial matrix of cells, results of earthquake expected magnitude parameters are then calculated, mapped, contoured and discussed in the context of recognized seismotectonic zones (Hindu Kush, Karakorum–Himalaya, Chaman fault system and Makran–Kutch) which characterize the seismicity of Pakistan and the surrounding region (Afghanistan, Tajikistan and India).

A probabilistic seismic hazard assessment of southern Peru and Northern Chile

Southern Peru and northern Chile (17–30°S, 67–74°W) make up a seismically active region due to the convergence of the Nazca Plate and the South American Plate. The region has experienced a number of destructive earthquakes and tsunamis over the past few centuries, which have caused loss of human life and significant damage to infrastructure, highlighting the importance of seismic hazard assessment in the region. In fact, a reliable seismic hazard assessment is critical for developing policies for seismic hazard mitigation and risk reduction. In this study, we performed a probabilistic seismic hazard assessment (PSHA) of the study area based on an earthquake catalog that was very carefully analyzed. In earlier studies, we demonstrated that inappropriate treatment of the earthquake catalog can result in a serious bias in evaluations of seismicity parameters (e.g., a bias of up to 42% in the “b” parameter of the Gutenberg–Richter law). To address this issue, we compiled a homogenous earthquake catalog consisting of 39,977 events during the 1513–2016 period and accounted for site-specific local effects by developing site-specific scaling relationships between different measures of magnitude (e.g., mb, Ms, MD) and moment magnitude (Mw). The study area was subdivided into 15 seismogenic zones, accounting for site-specific seismicity patterns. The parameters “a” and “b” of the Gutenberg–Richter law were estimated for each zone based on independent earthquake events. The PSHA was performed using a standard logic tree approach, which allowed us to systematically take into account the model-based uncertainty and its influence on the estimated ground motion parameters. Uniform hazard spectra for return periods of 475 and 2475 years were estimated for peak ground accelerations and spectral accelerations at 0.2 s and 1.0 s to meet the definitions of seismic hazards provided by the International Building Code (IBC, International Code Council [ICC], 2009). This study is expected to provide a basis for design maps for building codes and emergency planning.

Homogenized earthquake catalog and b-value mapping for Ethiopia and its adjoining regions

The Ethiopian rift which is part of East African Rift system passes through the middle of the country making it one of the most seismically active regions in the world. Thus, significant and damaging earthquakes have been reported and recorded in the past in this region. A homogeneous earthquake catalog is of basic importance for studying the earthquake occurrence pattern in space and time and for many engineering applications including assessment of seismic hazard, estimation of peak ground accelerations and determination of long-term seismic strain rates.The first earthquake catalogue for Ethiopia was prepared by Pierre Gouin and later, different authors attempted to compile a catalogue using different time period intervals and different earthquake magnitude scales. The b-value mapping and its implication never done for Ethiopia and its environs. The main purpose of the study is therefore first compile and homogenize earthquake catalog of Ethiopia including Read Sea and Gulf of Aden regions into Moment magnitude Mw scale through completeness analysis in time and magnitudes. Secondly, mapping b-values for different Seismgenic regions and understand its implications for magma induced Seismicity in the regions.During the present study, a new homogenized earthquake catalog in moment magnitude scale (Mw), covering about 3814 events is prepared for Ethiopia including Red sea and Gulf of Aden regions. The present study area is bounded within Latitude (40N − 200)N and Longitude (340N − 480)N E and have a magnitude range of Mw (3.0–7.1) with a total coverage period of 56 years (1960 to 2016). The catalog has been analyzed for magnitude completeness (Mc) using Gutenberg’s Frequency Magnitude Distribution law and it is found to be complete respectively for Mc ≥ 4.6 ± 0.03, Mc ≥ 4.6 ± 0.03, Mc ≥ 3.2, Mc ≥ 3.1 and Mc ≥ 5.1 for Afar including red sea and Gulf of Aden, Afar rift and Dabbahu Volcano, Northern, Central, and Southern Main Ethiopian Rifts. Further, the corresponding average b-value of the regions Afar including Red Sea and Gulf of Aden, Afar and Dabbahu Volcano separately, Northern Main Ethiopian Rift, Central Main Ethiopian Rift and Southern Main Ethiopian Rift respectively are estimated to be 1.17 ± 0.05, 1.15 ± 0.05, 0.843, 0.826 and 1.03 with respective period of completeness from 2003 to 2014, 2005 to 2014, 2001 to 2003, 2001 to 2003 and 1960 to 2016 for the regions. Later, mapping of the b-values in the Gutenberg-Richter relation from the newly developed catalog was performed by binning the regions into minimum of 0.050x0.050 for Afar and Dabbahu region, 0.10x0.10 for Main Ethiopian rifts and 0.20x0.20 for the other regions. Thus, the b-value characteristics of various seismogenic zones within the area have been discussed. Hence, in this study, we clearly observed that magma chamber movement including mapping of volcanic centers and magmatic segments are mapped using b-values.

Probabilistic Seismic Hazard Assessment for Amaravathi Region, Andhra Pradesh

This article explains an analytical attempt that estimates seismic hazard for Amaravathi city. The present study has been carried out contemplating the available faults and epicentral data within a radius of 300km of the Amaravathi region. The homogenous earthquake catalogue has been prepared for Amaravathi region by Steep’s method. The seismic hazard parameters ―a‖ and ―b‖ for Amaravathi city were evaluated by Gutenberg-Ritcher method. The ―a‖ and ―b‖ values obtained as 4.69, 0.6468 respectively. The total 353 epicenters and 31 faults were considered in this seismic analysis for the estimate of PSHA for Amaravathi. The ground motion produced by the faults at this site has been estimated by using the regionspecific Ground Motion Prediction Equation (GMPE) developed by the raghukanth and lyenger (2007). The probability of occurrence of different magnitude classes was estimated. The hazard curves and mean annual rate of exceedance for Peak Ground Acceleration were calculated by using ground motion estimated in this area. The Uniform Hazard Response Spectrum (UHRS) for the ranging time periods between 0.1 – 4 seconds was prepared. PGA values for Amaravati region was found to be in between 0.001g to 0.3g from seismic hazard map that was prepared in this study

An examination of the nature and dynamics of seismogenesis in South California, USA, based on Non-Extensive Statistical Physics

We examine the nature of the seismogenetic system in South California, USA, by searching for evidence of complexity and non-extensivity in the earthquake record. We attempt to determine whether earthquakes are generated by a self-excited Poisson process, in which case they are independent, or by a Critical process, in which long-range interactions in non-equilibrium states are expected (correlation). Emphasis is given to background seismicity, i.e. to the rudimentary expression of the seismogenetic system. We use the complete and homogeneous earthquake catalogue published by the South California Earthquake Data Centre, in which aftershocks are either included, or have been removed by a stochastic declustering procedure. We examine multivariate cumulative frequency distributions of earthquake magnitudes, interevent time and interevent distance in the context of Non-Extensive Statistical Physics, which generalizes the additive Boltzmann-Gibbs thermodynamics to non-additive (non-extensive) dynamic systems. Our results indicate that the seismogenetic systems of South California are generally sub-extensive complex and certainly non-Poissonian. Background seismicity exhibits long-range interaction as evidenced by the overall increase of correlation observed by declustering the earthquake catalogues, as well as by the high correlation observed for earthquakes separated by long interevent distances. The results compare very well with those obtained in previous work for the seismogenetic systems of North California. Specifically, the Walker Lane – Eastern California Shear Zone on one hand, and the San Andreas Fault system – south California Continental Borderland region on the other, appear to comprise fault networks with different dynamics and expression. The former exhibits persistent, very high correlation and has attributes of (stationary) Self-Organized Criticality (SOC). The latter exhibits high correlation mainly at long ranges and has attributes of evolutionary of (Self-Organized) Criticality. All in all, our results are compatible with simulations of small-world fault networks in which free boundary conditions at the surface allow for self-organization and criticality to develop.

Seismotectonics of South Africa

Assessment of seismic hazard is challenging especially for low seismicity regions like southern Africa. There is very little knowledge in terms of the coupling between the seismicity and active faults leading to an incomplete dataset in terms of recurrence times and seismic zonation. Concerted efforts have been made to compile a seismotectonic map of South Africa that will assist in delineating seismic hotspots in order to carry out a proper seismic hazard assessment using state of the art methodologies. In preparing the map, a homogeneous earthquake catalogue was compiled from local, regional and international databases. Fault plane solutions and stress information were obtained from publications, reports and international organisations such as the ISC, USGS and Harvard CMT. Though few such data are available for South Africa, all collected information is vital in the effort to understand the tectonics and stress modelling of the region. Several faults have been identified as possibly active, though some of them have no significant seismicity associated with them. Through these efforts, a seismotectonic map of South Africa has now been prepared. It is hoped that the information in the seismotectonic map will contribute to the preparation of more accurate hazard assessments for South Africa. However, efforts continue to collect and improve collection methods of historical and instrumental seismicity data, as well as geological information to improve the available seismotectonic data for this region.

Statistical Completeness Analysis of Seismic Data

Earthquakes constitute one of the most powerful forces to which most civil engineering structures and historical constructions will ever be subjected; and thus designing and preserving structures to resist these forces is of utmost importance. The goal of earthquake-resistant design is to produce a structure or facility that can withstand a certain level of shaking without excessive damage. Seismic hazard analyses involve the quantitative estimation of ground shaking hazards at a particular site. The main objective of this study is to develop a homogeneous earthquake catalogue for the low seismic region Warangal from 1800 to 2016 by considering a circular radius of 500 km. The catalogue is declustered using the algorithm proposed by Uhrhammer (1986) for removal of foreshocks and aftershocks. All the events have been converted to moment magnitude scale for homogenization. Completeness analysis has been carried out using the method proposed by Stepp (1972) to determine the time interval in which the data is complete over different magnitude ranges. The analysis shows that for the magnitude range of 3.0 ≤ M ≤ 3.49, 3.5 ≤ M ≤ 3.99, 4.0 ≤ M ≤ 4.49, 4.5 ≤ M ≤ 4.99, 5.0 ≤ M ≤ 5.49 and M ≤ 5.49, the data is complete for the last 50 years (1967-2016), 60 years (1957-2016), 140 years (1867-2016) and 180 years (1837-2016) respectively. This study will provide a significant under-standing in distribution of earthquakes in Warangal region as well as the assessment of seismic hazard for the region.

PRELIMINARY RESULTS PART 1: INVESTIGATING OF EARTHQUAKE OCCURRENCES WITH DIFFERENT DISTRIBUTION MODELS IN THE MARMARA SEA AND SURROUNDING, TURKEY

In this study, we investigated earthquake occurrences with different distribution models in the Marmara Sea and surrounding, Turkey. We analyzed for all earthquake occurrences of M s magnitude of a reliable homogeneous earthquake catalogue to each instrumental other historical periods. So, we used Beta, Normal, Gamma, Lognormal and Weibull distributions for 6 different seismogenic source zones in the Marmara Sea. Later, we plotted Probability Density Function (PDF), Cumulative Distribution Function (CDF), Hazard Function (HF), Cumulative Hazard Function (CHF), Survival Function (SF), Probability Difference, P-P plot, Q-Q plot. We determined the best suitable model for the assessment of earthquake occurrences. After that, we applied Goodness of Fit for used all distributions and obtained test results. Goodness of Fit concerned Kolmogorov Smirnov (K-S), Anderson Darling and Chi-Squared tests. Consequently, we determined to used earthquake hazard analysis with different distribution models. This study can be helpful science humans to determined earthquake hazard analysis in the Marmara Sea and surrounding.

Up-to-date Probabilistic Earthquake Hazard Maps for Egypt

An up-to-date earthquake hazard analysis has been performed in Egypt using a probabilistic seismic hazard approach. Through the current study, we use a complete and homogenous earthquake catalog covering the time period between 2200 BC and 2015 AD. Three seismotectonic models representing the seismic activity in and around Egypt are used. A logic-tree framework is applied to allow for the epistemic uncertainty in the declustering parameters, minimum magnitude, seismotectonic setting and ground-motion prediction equations. The hazard analysis is performed for a grid of 0.5° × 0.5° in terms of types of rock site for the peak ground acceleration (PGA) and spectral acceleration at 0.2-, 0.5-, 1.0- and 2.0-s periods. The hazard is estimated for three return periods (72, 475 and 2475 years) corresponding to 50, 10 and 2% probability of exceedance in 50 years. The uniform hazard spectra for the cities of Cairo, Alexandria, Aswan and Nuwbia are constructed. The hazard maps show that the highest ground acceleration values are expected in the northeastern part of Egypt around the Gulf of Aqaba (PGA up to 0.4 g for return period 475 years) and in south Egypt around the city of Aswan (PGA up to 0.2 g for return period 475 years). The Western Desert of Egypt is characterized by the lowest level of hazard (PGA lower than 0.1 g for return period 475 years).

Seismic Hazard Assessment at Esfaraen‒Bojnurd Railway, North‒East of Iran

The objective of this study is to evaluate the seismic hazard at the Esfarayen-Bojnurd railway using the probabilistic seismic hazard assessment (PSHA) method. This method was carried out based on a recent data set to take into account the historic seismicity and updated instrumental seismicity. A homogenous earthquake catalogue was compiled and a proposed seismic sources model was presented. Attenuation equations that recently recommended by experts and developed based upon earthquake data obtained from tectonic environments similar to those in and around the studied area were weighted and used for assessment of seismic hazard in the frame of logic tree approach. Considering a grid of 1.2 × 1.2 km covering the study area, ground acceleration for every node was calculated. Hazard maps at bedrock conditions were produced for peak ground acceleration, in addition to return periods of 74, 475 and 2475 years.