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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 establishment of a unified earthquake catalog is a basic requirement for attaining a detailed seismological analysis and an improved seismic hazard assessment. Accordingly, the current research paper aims to present a reliable instrumental unified earthquake catalog for the northern part of Algeria. This unified catalog is compiled using regional empirical relationships derived from converting different magnitude scales to an advanced physical-based moment magnitude scale suggested in the recent literature and denoted by Mwg. The regression methodology used in this study is called the New General Orthogonal Regression approach (N.GOR), which was selected since it is the most trustworthy procedure for scaling the magnitudes to Mwg. To highlight the significance of using the N.GOR, the obtained outcomes of the scaling relations were compared with those issued from the conventional general orthogonal regression (GOR) method, which is deemed to be the most dependable methodology used worldwide for magnitude conversion problems. The unified earthquake catalog was assembled from 1954 to 2022. Reliably converting the original magnitudes into homogenized moment magnitude leads to a complete and consistent unified earthquake catalog. Indeed, the unified moment magnitude catalog presented in this paper could provide reliable data for studying earthquakes distribution and the assessment of seismic hazards in the north of Algeria. [ABSTRACT FROM AUTHOR]

Epistemic uncertainty offers alternatives on decision making and various possibilities of computing the hazard integral. Generally, the logic tree approach is used while treating the epistemic uncertainty. Logic tree weight calculation is a subjective decision based on the degree of belief of the analyst on the possible contributors to the epistemic uncertainty and often leads to a different set of values by different researchers. This paper aims to develop a framework of accounting for the epistemic uncertainty in probabilistic seismic hazard analysis (PSHA) by minimizing the subjectivity involved in weight calculation. Guidelines/rules are developed for the weight calculation at each node of the logic tree. Recurrence parameters, magnitude and distance probability distributions, maximum magnitude, and selection of ground motion predictive equations (GMPEs) are considered the possible sources of epistemic uncertainty. A GMPE rule is proposed to be used with the PSHA framework to account for the propagation of epistemic uncertainty. The north-east region of India is chosen for the purpose of illustration. The study region is divided into seven seismic source zones (five in the active crustal region and two in the subduction zone). Seismic hazard is characterized in terms of the weighted mean and fractile representation of hazards using the logic tree approach. Only one sample illustration of the results are reported in terms of weighted mean and fractile representation of hazard curves and uniform hazard spectra (UHS). Further illustration of the PSHA results with possible implications from the epistemic uncertainty is reported in the companion paper. [ABSTRACT FROM AUTHOR]

Inspired by the first workshop on Best Practices in Physics-Based Fault Rupture Models for Seismic Hazard Assessment of Nuclear Installations (BestPSHANI) conducted by the International Atomic Energy Agency (IAEA) on 18-20 November, 2015 in Vienna (), this PAGEOPH topical volume collects several extended articles from this workshop as well as several new contributions. A total of 17 papers have been selected on topics ranging from the seismological aspects of earthquake cycle simulations for source-scaling evaluation, seismic source characterization, source inversion and ground motion modeling (based on finite fault rupture using dynamic, kinematic, stochastic and empirical Green's functions approaches) to the engineering application of simulated ground motion for the analysis of seismic response of structures. These contributions include applications to real earthquakes and description of current practice to assess seismic hazard in terms of nuclear safety in low seismicity areas, as well as proposals for physics-based hazard assessment for critical structures near large earthquakes. Collectively, the papers of this volume highlight the usefulness of physics-based models to evaluate and understand the physical causes of observed and empirical data, as well as to predict ground motion beyond the range of recorded data. Relevant importance is given on the validation and verification of the models by comparing synthetic results with observed data and empirical models. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard assessment of North-East India is carried out considering the GMPE rule and framework developed in the companion paper to account for the propagation of epistemic uncertainty. Seismic hazard is characterized in terms of weighted mean and fractile representation using a logic tree approach. Target conditional spectra with different conditional time periods are estimated by two methods: considering GMPE-specific generalized causal rupture and all contributing causal rupture scenarios. Results are reported with 2475- and 475-year return periods. The ratio of fractile to weighted mean representation of hazard is proposed as an alternative viewpoint of the importance factor used in seismic design. [ABSTRACT FROM AUTHOR]

In recent years the International Atomic Energy Agency (IAEA) has been closely following and supporting the use of physics-based rupture models for ground motion prediction (e.g. IAEA Safety Standards Series No. SSG–9 and Safety Report Series No. 85) as well as for fault displacement prediction (IAEA-TECDOC, in preparation), respectively for applications in Seismic Hazard Analysis (SHA) and Fault Displacement Hazard Analysis (FDHA) for nuclear installations. Further strengthening of this effort and dissemination in practices for SHA, FDHA and engineering issues have been done through different international working group activities, being the most outstanding two international workshops on Best Practices in Physics-based Fault Rupture Models for Seismic Hazard Assessment of Nuclear Installations (BestPSHANI) in 2015 and 2018. A PAGEOPH topical volume for the BestPSHANI 2015 was published in Dalguer et al. (Pure Appl Geophys 174:3325–3329, 2017). Now, in this PAGEOPH topical volume we collect several articles from the BestPSHANI 2018 workshop as well as several new contributions. The issue also covers further topics on the assessments of engineering issues that rely on ground motion estimates for the evaluation of structures oriented to full seismic risk analysis. A total of twenty-nine papers have been selected covering topics ranging from the seismological aspects of earthquake source studies, ground motion and fault displacement modeling to the engineering application of simulated ground motion for the analysis of soil structure interaction, structural response and fragility curve analysis for the quantification of seismic vulnerability of structures and their seismic performance. Collectively, the seismological papers discuss several current issues of source characterization and ground motion prediction for SHA, highlighting the usefulness of physics-based models for future applications in practice. The engineering papers describe methodologies to develop integral models from source-to-structures that consider the developments of synthetic seismograms as input for structural response and fragility curves estimation for seismic vulnerability assessment. Therefore, this issue contents advanced seismological and engineering resources that might be useful to scientists, engineers, students and practitioners involved in all aspects of SHA, FDHA and vulnerability analysis of engineering structures for seismic risk. [ABSTRACT FROM AUTHOR]

Because of the scarcity of recorded seismic ground motions from Vrancea intermediate-depth source that can be used in designing a structure, engineers are bound to use scaled, artificial, or simulated accelerograms. Out of these options, the first two might incompletely account for the phenomena that may appear. Although complicated, simulated accelerograms provide one of the best options for defining the seismic demand in engineering design, but further research is needed to adapt the simulation methods to the source, path, and site-specific characteristics. As some parameters used in simulations were not addressed yet specifically for the Vrancea-intermediate seismic source, the specific path duration is investigated in this paper. Using a database with the recorded ground motions from March 4, 1977, August 30, 1986, May 30 and May 31, 1990, October 27, 2004 Vrancea earthquakes (the only five recorded earthquakes with moment magnitudes at least equal to 6), the path and magnitude dependent duration specific to Vrancea intermediate-depth seismic source to be used in the stochastic simulation is developed. [ABSTRACT FROM AUTHOR]

The Lebanese Restraining Bend is an active bend along the Dead Sea Transform Fault in the eastern Mediterranean region where several destructive earthquakes have occurred throughout history. In this paper, we assess the gross features of the seismic hazard of the Lebanese Restraining Bend by applying a neo-deterministic method that involves the generation of synthetic seismograms distributed on a regular grid over the study area. We use the regional seismicity, seismic source zones, focal mechanism solutions, and velocity structural models. We present maps of ground displacement, velocity, and acceleration. This is the first study that generates neo-deterministic seismic hazard maps for the Lebanese Restraining Bend using representative ground motion modeling. Our results show that displacement values of 15–30 cm and velocity values of 30–60 cm/s can be expected along most of Lebanon. In addition, 0.15–0.30 g acceleration values can dominate most of the Lebanese territory and surrounding areas. It is evident from these results that the study area in general and Lebanon in particular constitute a high seismic hazard area, which necessitates further attention from the authorities regarding the precaution measures needed to mitigate the effects of potential catastrophic seismic events; in addition, more detailed investigations are needed at local scale for specific sites of interest. [ABSTRACT FROM AUTHOR]

Seismic risk analyses derive from earthquake catalogs a recurrence relation linking earthquake activity rate to magnitude. The most widely employed model is the log-linear Gutenberg–Richter relation (Gutenberg and Richter, Science, 83, 183–185, 1936; Gutenberg and Richter, Bulletin of the Seismological Society of America, 46(3), 105–145, 1945), with modifications at larger magnitudes (Cosentino et al., Bulletin of the Seismological Society of America, 67, 1615–1623, 1977; Kijko and Sellevoll, Bulletin of the Seismological Society of America, 79(3), 644–654, 1989; Page, Bulletin of the Seismological Society of America, 58, 1131–1168, 1968; Pisarenko and Sornette, Pure and Applied Geophysics, 160, 2343–2364, 2003; Turcotte, Physics of the Earth and Planetary Interiors, 111, 275–293, 1999). This relation leads to exponentially distributed magnitudes truncated to a maximum magnitude, a priori fixed under geophysical considerations. In this paper, we assume seismic events occur according to a Poisson distribution, but we propose to model the tail distribution of magnitudes with a generalized Pareto distribution (GPD). The GPD parameters are estimated with a maximum likelihood procedure. This GPD-based model gives rise to a new recurrence model that differs from the Gutenberg–Richter Law. It eliminates the need to introduce a maximum magnitude in the analysis that is difficult to determine. This paper details the expression of the estimators of the GPD parameters and the asymptotic normal distribution when the shape parameter ξ > - 1 . This asymptotic distribution yields confidence intervals for all parameters. The GPD parameter estimators account for the following features of the data set: (a) seismic events are collected on periods whose span depends on their magnitudes; (b) magnitudes are imprecisely known: each magnitude is supposed to uniformly belong to an interval of length 0.5. Our new model is estimated from information coming from the FCAT17 catalog. This catalog collects seismic events from the Alps region in France. We conduct an uncertainty analysis, and we quantify the impact of estimation uncertainty on the recurrence model. [ABSTRACT FROM AUTHOR]

A path for testing a probabilistic seismic hazard assessment (PSHA) map is presented in this paper via the evaluation of fortification benefit with two indices, economic benefit and safety benefit. The effect of fortification intensity on the vulnerability of the engineering structure is emphasized in the damage estimation of the evaluation. The expected losses and casualties are calculated based on the total areas in each of the five damage states with local parameters. The result of a case study of the 1990 PSHA map of China shows that the expected total reduction of loss from the damage to brick concrete and reinforced concrete buildings constructed during the in-service period of the map and damaged in the subsequent destructive earthquakes is RMB 216.5 billion. Thus the expected economic benefit is RMB 17.5 billion in comparison to the additional fortification cost of RMB 199.0 billion. The expected casualty reductions are 20,838 fewer deaths and 77,801 fewer serious injuries. This indicates that the implementation of the 1990 PSHA map has indeed played a beneficial role in earthquake disaster mitigation. The evaluation result of the marginal benefit of fortification, in terms of increasing or decreasing the fortification intensities by one degree further for the whole country, shows that the fortification level adopted in China is appropriate as a whole. [ABSTRACT FROM AUTHOR]

The goal of many earthquake engineering analyses is to ensure that a structure can withstand a given level of ground shaking while maintaining a desired level of performance. But there is a great deal of uncertainty about the numerous factors that impact the level of ground shaking. probabilistic seismic hazard analyses (PSHA) aim to quantify these uncertainties and combine them to produce an explicit description of the distribution of future shaking that may occur at a site. Among others, the distribution of the magnitudes is required by PSHA. This paper presents a new approach to estimate both the tail distribution of earthquake magnitudes and the tail distribution of the maximum earthquake magnitude over a year. This approach uses extreme value models based on Poisson process. The main innovations consist of combining the use of the generalized Pareto distribution (GPD) to model the tail distribution of earthquake magnitudes and the exact relation leading to the tail distribution of the annual maximum earthquake magnitude. We also propose a statistical inference that takes into account the growing incompleteness of the data in earlier times, which enables us to use as much available data as we can. This paper also provides a sensitivity analysis, which quantifies the robustness of the results with respect to two types of uncertainty: the statistical uncertainty due to the limited number of data used for the statistical inference and the uncertainty related to the determination of the complete observation periods of time by the seismologists. We detail validation tests to check the main assumptions underlying the probabilistic model: the Poisson occurrences of earthquakes and the GPD behavior of the tail distribution. The methodology is applied to an area located in the south of France, which provides estimates of some extreme quantiles of the annual maximum earthquake magnitude. [ABSTRACT FROM AUTHOR]

According to theory, earthquakes may produce disturbances in surrounding areas and affect the major earthquake occurrence rate of surrounding faults. The MS 6.6 Jinghe Earthquake on 9th August, 2017 occurred in the Tienshan Seismic Belt where there is much tectonic activity and many strong earthquakes occur. The impact of this earthquake on major earthquake activity of surrounding areas is worth studying. This paper attempts to combine two models: the Brownian passage-time (BPT) model, which describes the quasi-periodic recurrence of major earthquakes, and the Coulomb Failure Stress model, which describes rock failure on faults. The amount of change in the rate of major earthquake occurrence caused by a nearby earthquake was calculated, and changes in major earthquake activity in the surrounding areas after the Jinghe Earthquake were re-estimated. There are few differences in major earthquake occurrence rate change by stress disturbances calculated with the BPT model or the Coulomb Failure Stress model. Calculation results are consistent with actual earthquake cases. The 2017 Jinghe Earthquake increased major earthquake activity on the Boluokenu Fault and Yili Basin North Fault, and the expected major earthquake recurrence times of the two faults were advanced by 11 years and 59 years, respectively. Conclusions of this paper provide a reference for time-dependent seismic hazard assessments in related areas. [ABSTRACT FROM AUTHOR]

This paper evaluates the use of multisite (MS) probabilistic seismic hazard analysis (PSHA), which estimates the annual exceedance rate of a given level of ground motion in at least one of several sites as one of several possible results. For this purpose, (1) MS-PSHA is implemented through the Monte Carlo approach, taking into account various area sizes and correlation distances (CDs), and then (2) two proposals are represented as applications of MS-PSHA outcomes, both with reference to Sarpol-e Zahab City, a seismically active region located in the west of Iran. The first proposal attempts to determine the current code design probability of exceedance in at least one site, and the second one defines collapse prevention levels based on different probabilities of exceedance in at least one site. The efficiency of the results is discussed mainly by comparing them to recorded peak ground accelerations (PGAs) of three earthquakes, including the 2017 Sarpol-e Zahab 7.3 Mw event that largely exceeded the code design spectrum. MS-PSHA results demonstrate reasonable performance both in determining design ground motions and evaluating current design code when the exact seismic parameters of the study area are used in the analysis. Moreover, developed code-type design spectra based on MS-PSHA provided safety against collapse compared to a recently occurring low-probability event. MS estimates for various CDs and probabilities of exceedance in at least one site can also provide flexible design strategies regarding the importance of a structure and expected damage on a regional scale. [ABSTRACT FROM AUTHOR]

In recent decades, prediction of ground motion at a specific site or a region is of primary interest in probabilistic seismic hazard assessment (PSHA). Historically, several ground motion prediction equation (GMPE) models with different functional forms have been published using strong ground motion records available from NGA-West and European databases. However, low-to-moderate seismicity regions, such as Central & Eastern United States and western Europe, is characterized by limited strong-motion records in the magnitude–distance range of interest for PSHA. In these regions, the available data for the development of empirical GMPEs is very scarce and limited to small magnitude events. For these regions, the general practice in PSHA is to consider a set of GMPEs developed from data sets collected in other regions with high seismicity. This practice generates an overestimation of the seismic hazard for the low seismicity regions. There are two potential solutions to overcome this problem: (1) a new GMPE model can be developed; however, development of such a model can require significant amount of data which is not usually available, and (2) the existing GMPE models can be recalibrated based on the data sets collected in the new region rather than developing a new GMPE model. In this paper, we propose a methodological approach to recalibrate the coefficients in a GMPE model using different algorithms to perform Bayesian inference. The coefficients are recalibrated for a subset of European Strong-Motion (ESM) database that corresponds to low-to-moderate seismicity records. In this study, different statistical models are compared based on the functional form given by the chosen GMPE, and the best model and algorithm are recommended using the concept of information criteria. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic seismic hazard assessment (PSHA) for Guilan Province, an influential, highly populated and strategic district to the south of the Caspian Sea in northern Iran. In this study, the peak ground acceleration (PGA) and spectral acceleration (SA) over bedrock are estimated for the whole area of the province. NGA-West2 and the EMME project attenuation relationships are applied and combined using the logic tree method. Seismic hazard assessment is then carried out to establish the maps of seismic hazard distribution based on PGA values for two hazard levels as suggested by the Iranian seismic code of practice. Finally, deaggregation analysis is performed to determine the magnitude and distance pair that most prominently contributes to the seismic hazard for each district, which is of great importance for the region, as this has not been done before. Comparing the results with those suggested by the Iranian seismic code of practice and those obtained by previous studies, a general agreement seems to exist, although some violations are observed for some areas, especially in the southeastern part of the province, highlighting a need for revision of the Iranian seismic code of practice. [ABSTRACT FROM AUTHOR]

The aim of this study is to conduct a probabilistic seismic hazard analysis and spatial variation of seismic hazard at the surface level for Northeast of Algeria, covering 4°E–9°E, 33°N–38°N. The most recent peak ground acceleration (PGA) attenuation relationship, along with the updated seismic catalog and the best knowledge on the seismic activity in the study area have been used to estimate the seismic hazard and its uncertainty. Two types of seismic source models, linear sources and areal sources, were considered to model the seismic sources. Different sets of ground motion prediction equations were used for different tectonic provinces to characterize the attenuation properties. The hazard estimation at bedrock level was carried out using a probabilistic approach and the results obtained from various methodologies were combined into a logic tree framework. In this paper, we generate PGA maps with 10% probability of exceedance in 50 years, for a rock site condition. The seismic site characterization of Algeria was done using topographic slope map derived from Digital elevation model data. We estimate the seismic hazard from the seismicity catalog and not from faults with recurrence rates obtained from geologic data. The hazard estimation at surface level, is achieved through the use of appropriate site amplification factors corresponding to various site classes based on topographic gradient. Spatial variation of surface level PGA for return periods of 100, 475 years and 2000 years are presented as contour maps. The maps obtained in this study are based on the assumption that the process of earthquake occurrence is inherently Poissonian, so that the probabilistic ground motion is time-independent. [ABSTRACT FROM AUTHOR]

In this paper seismic hazard for the sourthern slope of the Greater Caucasus (Azerbaijan) was assessed by using five major parameters: moment magnitude, simulated peak ground acceleration (PGA) from four target earthquakes, intensity scenario, amplification factor and b value. The deterministic scenario-based seismic hazard assessment method was applied by using the seismic catalogues compiled by the Republican Center of Seismological Survey at Azerbaijan National Academy of Sciences. Additionally this study presents hazard assessment analysis on 67 active faults tracing in the southern slope of the Greater Caucasus, considering the fault's location, size and length, and calculating the magnitude for those faults and lineaments estimated by empirical correlations. Our findings are: (1) maximum earthquake of Mw 8.0 is estimated for the western area zone and is used to generate one of the seismic scenarios of the region; (2) intensity distribution classifies the region into the highest hazard level with intensity value of 7 and over in the westward part and also in the eastward of the studied territory, in contrast to some areas in the southern part of the region which has the lowest level with intensity value of 6 and over; (3) the b value distribution shows that lower values are observed in the western part of the region (Zagatala, Sheki), in the Shamakhi area and on some areas of the northern part indicating higher stress in those areas; (4) PGA map from scenario earthquakes demonstrates that the very high PGAs are scattered in the west and east parts of the study area, while independently from the epicenter of the target earthquakes, the low and very low PGA is scattered in the central part of the study area. Such seismic hazard analysis with consideration of one of the main five parameters and target earthquake scenarios could help the region's sustainable development against earthquakes. [ABSTRACT FROM AUTHOR]

The Chilean subduction zone is one of the most active of the world with M = 8 or larger interplate thrust earthquakes occurring every 10 years or so on the average. The identification and characterization of pulses propagated from dominant asperities that control the rupture of these earthquakes is an important problem for seismology and especially for seismic hazard assessment since it can reduce the earthquake destructiveness potential. A number of studies of large Chilean earthquakes have revealed that the source time functions of these events are composed of a number of distinct energy arrivals. In this paper, we identify and characterize the high frequency pulses of dominant asperities using near source strong motion records. Two very well recorded interplate earthquakes, the 1985 Central Chile (Ms = 7.8) and the 2007 Tocopilla (Mw = 7.7), are considered. In particular, the 2007 Tocopilla earthquake was recorded by a network with absolute time and continuos recording. From the study of these strong motion data it is possible to identify the arrival of large pulses coming from different dominant asperities. The recognition of the key role of dominant asperities in seismic hazard assessment can reduce overestimations due to scattering of attenuation formulas that consider epicentral distance or shortest distance to the fault rather than the asperity distance. The location and number of dominant asperities, their shape, the amplitude and arrival time of pulses can be one of the principal factors influencing Chilean seismic hazard assessment and seismic design. The high frequency pulses identified in this paper have permitted us to extend the range of frequency in which the 1985 Central Chile and 2007 Tocopilla earthquakes were studied. This should allow in the future the introduction of this seismological result in the seismic design of earthquake engineering. [ABSTRACT FROM AUTHOR]

This paper begins with a critical assessment of the concept of macroseismic intensity, on which traditional scales, such as MSK and EMS, are based. The main shortcoming identified is the model's failure to consider the spectral features of ground motion. This omission may lead to erroneous seismic zonation, as shown in the paper. As a result, the model is of little interest to engineers who must design and build safe structures while adopting economical solutions. The paper presents a way to radically improve this situation. The starting point for this approach was the experience of the destructive Vrancea earthquake of 1977.03.04, which made it clear that intensity appears to be different for structures having natural periods pertaining to different spectral domains. The solution proposed to the shortcomings of the traditional intensity concept is postulated on a system of analytical expressions, covering definitions of global intensities, of intensities related to oscillation frequency and of intensities related to a definite spectral band. The latter definition lies at the basis of a definition of discrete intensity spectra. Illustrative applications are presented, in relation to global intensities and to discrete intensity spectra. We then analyze an illustrative case in which the use of traditional macroseismic survey techniques led to erroneous seismic zonation. Finally, some conclusions and recommendations are presented. Based on the authors' long-term experience, we strongly recommend close interaction between seismologists and engineers in working groups and joint projects targeted on radical improvement of the basic concepts of seismic intensity and of specific analysis procedures. [ABSTRACT FROM AUTHOR]

The main objective of this paper was to introduce the Environmental Seismic Intensity scale (ESI), a new scale developed and tested by an interdisciplinary group of scientists (geologists, geophysicists and seismologists) in the frame of the International Union for Quaternary Research (INQUA) activities, to the widest community of earth scientists and engineers dealing with seismic hazard assessment. This scale defines earthquake intensity by taking into consideration the occurrence, size and areal distribution of earthquake environmental effects (EEE), including surface faulting, tectonic uplift and subsidence, landslides, rock falls, liquefaction, ground collapse and tsunami waves. Indeed, EEEs can significantly improve the evaluation of seismic intensity, which still remains a critical parameter for a realistic seismic hazard assessment, allowing to compare historical and modern earthquakes. Moreover, as shown by recent moderate to large earthquakes, geological effects often cause severe damage'; therefore, their consideration in the earthquake risk scenario is crucial for all stakeholders, especially urban planners, geotechnical and structural engineers, hazard analysts, civil protection agencies and insurance companies. The paper describes background and construction principles of the scale and presents some case studies in different continents and tectonic settings to illustrate its relevant benefits. ESI is normally used together with traditional intensity scales, which, unfortunately, tend to saturate in the highest degrees. In this case and in unpopulated areas, ESI offers a unique way for assessing a reliable earthquake intensity. Finally, yet importantly, the ESI scale also provides a very convenient guideline for the survey of EEEs in earthquake-stricken areas, ensuring they are catalogued in a complete and homogeneous manner. [ABSTRACT FROM AUTHOR]

The epidemic type aftershock sequence (ETAS) statistical model of aftershock seismicity combines various earthquake scaling relations to produce synthetic earthquake catalogs, or estimates of aftershock seismicity rates, based on recent earthquake activity. One challenge to ETAS-based hazard assessment is the large number of free parameters involved. In this paper, we introduce an approach to constrain this parameter space from canonical scaling relations, empirical observations, and fundamental physics. We show that ETAS parameters can be estimated as a function of an earthquake's magnitude m based on the finite temporal and spatial extents of the rupture area. This approach facilitates fast ETAS-based estimates of seismicity from large 'seed' catalogs, and it is particularly well suited to web-based deployment and otherwise automated implementations. It constitutes a significant improvement over contemporary ETAS by mitigating variability related to instrumentation and subjective catalog selection. [ABSTRACT FROM AUTHOR]

Statistical quantification of observed seismicity is important for understanding earthquake dynamics and future risk in any seismic-prone region. In this paper, we implement the idea of nowcasting (Rundle et al. in Earth and Space Science 3:480–486, 2016) to examine the current uncertain state of earthquake hazard assessment in the seismically active Bay of Bengal (BoB) and adjacent regions. First, we utilize the concept of "natural time" (Varostos et al. in Physical Review E 71:032102, 2005), rather than clock time, to develop a statistical distribution of inter-event counts of "small" earthquakes occurring between "large" earthquakes. Using relevant statistics of natural time, we then calculate the earthquake potential score (EPS) as the cumulative number of small earthquakes since the last large event in the selected region. The EPS, which provides the nowcast value for a region, reveals the current state of earthquake hazard in that region. Therefore, by indirect means, the EPS provides us with a simple yet transparent estimation of the current level of seismic progress through the regional earthquake cycle of recurring events in a geographical area. To illustrate the nowcasting approach in the study region, we computed EPS values for the two most seismically exposed megacities, Dhaka and Kolkata, considering events of M ≥ 4 within a radius of 250 km around their respective city centers. We found that the current EPS values corresponding to M ≥ 6 events in Dhaka and Kolkata were approximately 0.72 and 0.40, respectively. The practical applicability of these values is discussed in conjunction with sensitivity analysis of the threshold magnitudes. [ABSTRACT FROM AUTHOR]

The evaluation of evidence provided by geological studies and historical catalogs indicates that in some seismic regions and faults, multiple large earthquakes occur in cluster. Then, the occurrences of large earthquakes confront with quiescence and only the small-to-moderate earthquakes take place. Clustering of large earthquakes is the most distinguishable departure from the assumption of constant hazard of random occurrence of earthquakes in conventional seismic hazard analysis. In the present study, a time-dependent recurrence model is proposed to consider a series of large earthquakes that occurs in clusters. The model is flexible enough to better reflect the quasi-periodic behavior of large earthquakes with long-term clustering, which can be used in time-dependent probabilistic seismic hazard analysis with engineering purposes. In this model, the time-dependent hazard results are estimated by a hazard function which comprises three parts. A decreasing hazard of last large earthquake cluster and an increasing hazard of the next large earthquake cluster, along with a constant hazard of random occurrence of small-to-moderate earthquakes. In the final part of the paper, the time-dependent seismic hazard of the New Madrid Seismic Zone at different time intervals has been calculated for illustrative purpose. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the authors discuss various reports within the issue on topics including earthquake early warning systems (EEWS), the physical basis of earthquake and tsunami occurrences and the occurrence of large earthquakes in the Ibero- Maghrebian region.

Microzonation deals with classifying seismic hazards in terms of ground motions resulting from amplification of seismic waves by nature of soil profiles underlying a site, town or city. This paper presents the results of microzonation study for Islamabad metropolitan, the capital of Pakistan. Cumulative SPT- N values from geophysical borehole and microtremor (Tromino Engy Plus) data were used to classify the soils into classes C (very dense soil profile and soft rock) and D (stiff soil profile) as devised by the National Earthquake Hazard Reduction Program (NEHRP). Soil response analyses were carried out based on scaled time histories of Kashmir earthquake (2005, 0.02 g), Mangla earthquake (2006, 0.031 g) and Haripur earthquake (2010, 0.13 g) corresponding to return periods of 150, 475, 975 and 2475 years. Spectral accelerations on the ground surface are calculated by two different approaches (1) soil response analysis performed using one dimensional shear wave propagation method (equivalent linear approach); and (2) NEHRP and Borcherdt amplification factors. Microzonation maps are produced with respect to ground shaking intensity for the return periods of 150, 475, 975 and 2475 years taking into account the variation of the spectral accelerations calculated based on these two procedures. The results show that the accelerations at the ground surface in the Islamabad-Rawalpindi metropolitan are in the range of 0.40-0.48 g (for 150 years), 0.59-0.65 g (for 475 years), 0.71-0.77 g (for 975 years), and 0.92-0.94 g (for 2475 years). The amplification factors for these four hazard levels range from 0.96 to 1.38 (150 years), 0.90-1.14 (475 years), 0.85-1.04 (975 years) and 0.84-1.00 (2475 years). [ABSTRACT FROM AUTHOR]

We argue that for critical structures near large earthquake sources: (1) the ergodic assumption, recent history, and simplified descriptions of the hazard are not appropriate to rely on for earthquake ground motion prediction and can lead to a mis-estimation of the hazard and risk to structures; (2) a physics-based approach can address these issues; (3) a physics-based source model must be provided to generate realistic phasing effects from finite rupture and model near-source ground motion correctly; (4) wave propagations and site response should be site specific; (5) a much wider search of possible sources of ground motion can be achieved computationally with a physics-based approach; (6) unless one utilizes a physics-based approach, the hazard and risk to structures has unknown uncertainties; (7) uncertainties can be reduced with a physics-based approach, but not with an ergodic approach; (8) computational power and computer codes have advanced to the point that risk to structures can be calculated directly from source and site-specific ground motions. Spanning the variability of potential ground motion in a predictive situation is especially difficult for near-source areas, but that is the distance at which the hazard is the greatest. The basis of a 'physical-based' approach is ground-motion syntheses derived from physics and an understanding of the earthquake process. This is an overview paper and results from previous studies are used to make the case for these conclusions. Our premise is that 50 years of strong motion records is insufficient to capture all possible ranges of site and propagation path conditions, rupture processes, and spatial geometric relationships between source and site. Predicting future earthquake scenarios is necessary; models that have little or no physical basis but have been tested and adjusted to fit available observations can only 'predict' what happened in the past, which should be considered description as opposed to prediction. We have developed a methodology for synthesizing physics-based broadband ground motion that incorporates the effects of realistic earthquake rupture along specific faults and the actual geology between the source and site. [ABSTRACT FROM AUTHOR]

It is obvious that the problem of precise assessment and/or analysis of seismic hazard (SHA) is quite a serious issue, and seismic risk reduction considerably depends on it. It is well known that there are two approaches in seismic hazard analysis, namely, deterministic (DSHA) and probabilistic (PSHA). The latter utilizes statistical estimates of earthquake parameters. However, they may not exist in a specific region, and using PSHA it is difficult to take into account local aspects, such as specific regional geology and site effects, with sufficient precision. For this reason, DSHA is preferable in many cases. After the destructive 1988 Spitak earthquake, the SHA of the territory of Armenia has been revised and increased. The distribution pattern for seismic risk in Armenia is given. Maximum seismic risk is concentrated in the region of the capital, the city of Yerevan, where 40% of the republic's population resides. We describe the method used for conducting seismic resistance assessment of the existing reinforced concrete (R/C) buildings. Using this assessment, as well as GIS technology, the coefficients characterizing the seismic risk of destruction were calculated for almost all buildings of Yerevan City. The results of the assessment are presented. It is concluded that, presently, there is a particularly pressing need for strengthening existing buildings. We then describe non-conventional approaches to upgrading the earthquake resistance of existing multistory R/C frame buildings by means of Additional Isolated Upper Floor (AIUF) and of existing stone and frame buildings by means of base isolation. In addition, innovative seismic isolation technologies were developed and implemented in Armenia for construction of new multistory multifunctional buildings. The advantages of these technologies are listed in the paper. It is worth noting that the aforementioned technologies were successfully applied for retrofitting an existing 100-year-old bank building in Irkutsk (Russia), for retrofit design of an existing 177-year-old municipality building in Iasi (Romania) and for construction of a new clinic building in Stepanakert (Nagorno Karabakh). Short descriptions of these projects are presented. Since 1994 the total number of base and roof isolated buildings constructed, retrofitted or under construction in Armenia, has reached 32. Statistics of seismically isolated buildings are given in the paper. The number of base isolated buildings per capita in Armenia is one of the highest in the world. In Armenia, for the first time in history, retrofitting of existing buildings by base isolation was carried out without interruption in the use of the buildings. The description of different base isolated buildings erected in Armenia, as well as the description of the method of retrofitting of existing buildings which is patented in Armenia (M. G. Melkumyan, patent of the Republic of Armenia No. 579), are also given in the paper. [ABSTRACT FROM AUTHOR]

Dense strong motion observation networks provided us with valuable data for studying strong motion generation from large earthquakes. From kinematic waveform inversion of seismic data, the slip distribution on the fault surface of large earthquakes is known to be spatially heterogeneous. Because heterogeneities in the slip and stress drop distributions control the generation of near-source ground motion, it is important to characterize these heterogeneities for past earthquakes in constructing a source model for reliable prediction of strong ground motion. The stress changes during large earthquakes on the faults recently occurring in Japan are estimated from the detailed slip models obtained by the kinematic waveform inversion. The stress drops on and off asperities are summarized on the basis of the stress change distributions obtained here. In this paper, we define the asperity to be a rectangular area whose slip is 1.5 or more times larger than the average slip over the fault according to the previous study for inland crustal earthquakes. The average static stress drops on the asperities of the earthquakes studied here are in the range 6-23 MPa, whereas those off the asperities are below 3 MPa. We compiled the stress drop on the asperities together with a data set from previous studies of other inland earthquakes in Japan and elsewhere. The static stress drop on the asperity depends on its depth, and we obtained an empirical relationship between the static stress drop and the asperity's depth. Moreover, surface-breaking asperities seemed to have smaller stress drops than buried asperities. Simple ground motion simulations using the characterized asperity source models reveal that deep asperities generate larger ground motion than shallow asperities, because of the different stress drops of the asperities. These characteristics can be used for advanced source modeling in strong ground motion prediction for inland crustal earthquakes. [ABSTRACT FROM AUTHOR]

The paper considers Poisson temporal occurrence of earthquakes and presents a way to integrate uncertainties of the estimates of mean activity rate and magnitude cumulative distribution function in the interval estimation of the most widely used seismic hazard functions, such as the exceedance probability and the mean return period. The proposed algorithm can be used either when the Gutenberg-Richter model of magnitude distribution is accepted or when the nonparametric estimation is in use. When the Gutenberg-Richter model of magnitude distribution is used the interval estimation of its parameters is based on the asymptotic normality of the maximum likelihood estimator. When the nonparametric kernel estimation of magnitude distribution is used, we propose the iterated bias corrected and accelerated method for interval estimation based on the smoothed bootstrap and second-order bootstrap samples. The changes resulted from the integrated approach in the interval estimation of the seismic hazard functions with respect to the approach, which neglects the uncertainty of the mean activity rate estimates have been studied using Monte Carlo simulations and two real dataset examples. The results indicate that the uncertainty of mean activity rate affects significantly the interval estimates of hazard functions only when the product of activity rate and the time period, for which the hazard is estimated, is no more than 5.0. When this product becomes greater than 5.0, the impact of the uncertainty of cumulative distribution function of magnitude dominates the impact of the uncertainty of mean activity rate in the aggregated uncertainty of the hazard functions. Following, the interval estimates with and without inclusion of the uncertainty of mean activity rate converge. The presented algorithm is generic and can be applied also to capture the propagation of uncertainty of estimates, which are parameters of a multiparameter function, onto this function. [ABSTRACT FROM AUTHOR]

The probabilistic seismic hazard analysis for Romania is revisited within the framework of the BIGSEES national research project () financed by the Romanian Ministry of Education and Scientific Research in the period 2012-2016. The scope of this project is to provide a refined description of the seismic action for Romanian sites according to the requirements of Eurocode 8. To this aim, the seismicity of all the sources influencing the Romanian territory is updated based on new data acquired in recent years. The ground-motion models used in the analysis, as well as their corresponding weights, are selected based on the results from several recent papers also published within the framework of the BIGSEES project. The seismic hazard analysis for Romania performed in this study are based on the traditional Cornell-McGuire approach. Finally, the results are discussed and compared with the values obtained in the recently completed SHARE research project. The BIGSEES and SHARE results are not directly comparable since the considered soil conditions are different-actual soil classes for BIGSEES and rock for SHARE. Nevertheless, the analyses of the seismic hazard results for 200 sites in Romania reveal considerable differences between the seismic hazard levels obtained in the present study and the SHARE results and point out the need for further analyses and thorough discussions related to the two seismic hazard models, especially in the light of a possible future harmonized hazard map for Europe. [ABSTRACT FROM AUTHOR]

Real-time integration of multi-parametric observations is expected to accelerate the process toward improved, and operationally more effective, systems for time-Dependent Assessment of Seismic Hazard (t-DASH) and earthquake short-term (from days to weeks) forecast. However, a very preliminary step in this direction is the identification of those parameters (chemical, physical, biological, etc.) whose anomalous variations can be, to some extent, associated with the complex process of preparation for major earthquakes. In this paper one of these parameters (the Earth's emitted radiation in the Thermal InfraRed spectral region) is considered for its possible correlation with M ≥ 4 earthquakes occurred in Greece in between 2004 and 2013. The Robust Satellite Technique (RST) data analysis approach and Robust Estimator of TIR Anomalies (RETIRA) index were used to preliminarily define, and then to identify, significant sequences of TIR anomalies (SSTAs) in 10 years (2004-2013) of daily TIR images acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation satellite. Taking into account the physical models proposed for justifying the existence of a correlation among TIR anomalies and earthquake occurrences, specific validation rules (in line with the ones used by the Collaboratory for the Study of Earthquake Predictability-CSEP-Project) have been defined to drive a retrospective correlation analysis process. The analysis shows that more than 93 % of all identified SSTAs occur in the prefixed space-time window around ( M ≥ 4) earthquake's time and location of occurrence with a false positive rate smaller than 7 %. Molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space/time data gaps produced by the presence of clouds over the scene. Achieved results, and particularly the very low rate of false positives registered on a so long testing period, seems already sufficient (at least) to qualify TIR anomalies (identified by RST approach and RETIRA index) among the parameters to be considered in the framework of a multi-parametric approach to t-DASH. [ABSTRACT FROM AUTHOR]

The south of the Iberian Peninsula is of especial interest for the application of Earthquake Early Warning System (EEWS) technologies due to the past occurrence of damaging earthquakes such as the 1755 Lisbon earthquake. However, there are several critical issues that need to be addressed in order to develop an EEWS in this area. The first is the magnitude scale inhomogeneity of the available catalogues. A second is that most of the available broad-band seismograms for this area correspond to earthquakes with magnitudes less than 6.0, recorded at distances greater than 100 km, and sometimes with a low signal-to-noise ratio. And third, the occurrence of large earthquakes in this area means that the standard EEWS time window normally used needs to be tested in order to check whether it is long enough. Our paper describes the results of homogenizing the catalogue magnitudes by using empirical relationships to obtain the moment magnitude M. A criterion based on a threshold value for the signal-to-noise ratio is applied in order to avoid noise-contaminated seismogram data. An important part of the study is a check of whether the correlations previously obtained for south Iberia are valid for other neighbouring areas such as Algeria, and for larger earthquakes. Finally, since recent studies have shown that the larger the earthquake the longer the time window needed to properly estimate the magnitude, the window was increased progressively from 0 to 20 s in order to study the behaviour of the EEWS parameters for the largest earthquakes in the database. [ABSTRACT FROM AUTHOR]

Occurrence of a large earthquake could be predicted by anomalous temporal increase of the Load/Unload Response Ratio (LURR). Previous studies have indicated that the stress field that existed before a large earthquake may have a strong influence on the evaluation of LURR. In this paper, we replace the circular region usually adopted in LURR practice with an area within which the tectonic stress change would mostly affect the Coulomb stress on a potential seismogenic fault of a future event. This algorithm is devised to increase the sensitivity of LURR to measure criticality of stress accumulation before a large earthquake. In the algorithm, we assess the stress change and identify the areas with increased Coulomb stress before an earthquake using a simple back-slip dislocation model of the event. Retrospective tests of this algorithm on some disastrous earthquakes that occurred in the Chinese mainland in recent years show remarkable enhancement of the LURR precursory anomalies. By using the hypothetical faults for the large earthquake prediction, we further illustrate that the new algorithm is more sensitive to detect future earthquake of a particular magnitude range and location than the circular region algorithm. Hence, where sufficient information of the regional fault tectonics is given, the Coulomb stress algorithm can be used to augment current LURR technique for seismic hazard estimation. [ABSTRACT FROM AUTHOR]

We present a new method to identify semi-periodic sequences in the occurrence times of large earthquakes, which allows for the presence of multiple semi-periodic sequences and/or events not belonging to any identifiable sequence in the time series. The method, based on the analytic Fourier transform, yields estimates of the departure from periodicity of an observed sequence, and of the probability that the sequence is not due to chance. These estimates are used to make and to evaluate forecasts of future events belonging to each sequence. Numerous tests with synthetic catalogs show that the method is surprisingly capable of correctly identifying sequences, unidentifiable by eye, in complicated time series. Correct identification of a given sequence depends on the number of events it contains, on the sequence's departure from periodicity, and, in some cases, on the choice of starting and ending times of the analyzed time window; as well as on the total number of events in the time series. Some particular data combinations may result in spectra where significant periods are obscured by large amplitudes artifacts of the transform, but artifacts can be usually recognized because they lack harmonics; thus, in most of these cases, true semi-periodic sequences may not be identified, but no false identifications will be made. A first example of an application of the method to real seismicity data is the analysis of the Parkfield event series. The analysis correctly aftcasts the September 2004 earthquake. Further applications to real data from Japan and Venezuela are shown in a companion paper. [ABSTRACT FROM AUTHOR]

This paper investigates the suitability of a three-parameter (scale, shape, and location) Weibull distribution in probabilistic assessment of earthquake hazards. The performance is also compared with two other popular models from same Weibull family, namely the two-parameter Weibull model and the inverse Weibull model. A complete and homogeneous earthquake catalog ( Yadav et al. in Pure Appl Geophys 167:1331-1342, ) of 20 events ( M ≥ 7.0), spanning the period 1846 to 1995 from north-east India and its surrounding region (20°-32°N and 87°-100°E), is used to perform this study. The model parameters are initially estimated from graphical plots and later confirmed from statistical estimations such as maximum likelihood estimation (MLE) and method of moments (MoM). The asymptotic variance-covariance matrix for the MLE estimated parameters is further calculated on the basis of the Fisher information matrix (FIM). The model suitability is appraised using different statistical goodness-of-fit tests. For the study area, the estimated conditional probability for an earthquake within a decade comes out to be very high (≥0.90) for an elapsed time of 18 years (i.e., 2013). The study also reveals that the use of location parameter provides more flexibility to the three-parameter Weibull model in comparison to the two-parameter Weibull model. Therefore, it is suggested that three-parameter Weibull model has high importance in empirical modeling of earthquake recurrence and seismic hazard assessment. [ABSTRACT FROM AUTHOR]

A structural study in the SW section of the Colorado River delta using seismic reflection data is presented. The study area is located along the Cerro Prieto transform fault, which extends from the northern Gulf of California through the Mexicali Valley and is an active fault within the Pacific-North American plate boundary zone. The research was supported by a database of five seismic profiles with a total length of 215 km, collected in the early 80's by Petróleos Mexicanos. The results show a high density of faults, most of which are buried by sediments. Within the Cerro Prieto fault zone, several faults were identified, such as: Palmas, Mesa, and Pangas Viejas, until now unknown. In addition, even though the Indiviso fault was investigated and superficially identify prior to this work, herein mapped at depth. West of the Cerro Prieto fault zone lies the Las Tinajas basin, bound by the Dunas and Saldaña faults and by the Montague basin to the southeast. The deformation zone along the plate boundary is 18-km-wide, stretching from the Cerro Prieto fault in the east to the Pangas Viejas fault in the west. The orientations of the faults are NW-SE, and if projected from the southern side of the Sierra Cucapah southward, the faults tend to join the Cerro Prieto fault. In the Las Tinajas basin, the acoustic basement is deeper than 5,000 m. Some of the largest vertical displacements generated by the 2010 7.2-Mw El Mayor-Cucapah earthquake occurred southeast of the epicenter and coincided with the location of the Pangas Viejas Fault, which is buried by sediments. Before this event, seismic activity was very low, and no structures were known in the area. In this paper, we demonstrate that there are at least seven major faults that may now pose a high seismic hazard. [ABSTRACT FROM AUTHOR]

Three-dimensional frequency dependent S-wave quality factor (Q β(f)) value for the central Honshu region of Japan has been determined in this paper using an algorithm based on inversion of strong motion data. The method of inversion for determination of three-dimensional attenuation coefficients is proposed by H ashida and S himazaki (J Phys Earth. 32, 299–316, 1984 ) and has been used and modified by J oshi (Curr Sci. 90, 581–585, 2006 ; Nat Hazards. 43, 129–146, 2007 ) and J oshiet al. (J. Seismol. 14, 247–272, 2010 ). Twenty-one earthquakes digitally recorded on strong motion stations of Kik-net network have been used in this work. The magnitude of these earthquake ranges from 3.1 to 4.2 and depth ranging from 5 to 20 km, respectively. The borehole data having high signal to noise ratio and minimum site effect is used in the present work. The attenuation structure is determined by dividing the entire area into twenty-five three-dimensional blocks of uniform thickness having different frequency-dependent shear wave quality factor. Shear wave quality factor values have been determined at frequencies of 2.5, 7.0 and 10 Hz from record in a rectangular grid defined by 35.4°N to 36.4°N and 137.2°E to 138.2°E. The obtained attenuation structure is compared with the available geological features in the region and comparison shows that the obtained structure is capable of resolving important tectonic features present in the area. The proposed attenuation structure is compared with the probabilistic seismic hazard map of the region and shows that it bears some remarkable similarity in the patterns seen in seismic hazard map. [ABSTRACT FROM AUTHOR]

The territory of Lithuania and adjacent areas of the East European Craton have always been considered a region of low seismicity. Two recent earthquakes with magnitudes of more than 5 in the Kaliningrad District (Russian Federation) on 21 September 2004 motivated re-evaluation of the seismic hazard in Lithuania and adjacent territories. A new opportunity to study seismicity in the region is provided by the PASSEQ (Pasive Seismic Experiment) project that aimed to study the lithosphere-asthenosphere structure around the Trans-European Suture Zone. Twenty-six seismic stations of the PASSEQ temporary seismic array were installed in the territory of Lithuania. The stations recorded a number of local and regional seismic events originating from Lithuania and adjacent areas. This data can be used to answer the question of whether there exist seismically active tectonic zones in Lithuania that could be potentially hazardous for critical industrial facilities. Therefore, the aim of this paper is to find any natural tectonic seismic events in Lithuania and to obtain more general view of seismicity in the region. In order to do this, we make a manual review of the continuous data recorded by the PASSEQ seismic stations in Lithuania. From the good quality data, we select and relocate 45 local seismic events using the well-known LocSAT and VELEST location algortithms. In order to discriminate between possible natural events, underwater explosions and on-shore blasts, we analyse spatial distribution of epicenters and temporal distribution of origin times and perform both visual analysis of waveforms and spectral analysis of recordings. We show that the relocated seismic events can be grouped into five clusters (groups) according to their epicenter coordinates and origin and that several seismic events might be of tectonic origin. We also show that several events from the off-shore region in the Baltic Sea (at the coasts of the Kaliningrad District of the Russian Federation) are non-volcanic tremors, although the origin of these tremor-type events is not clear. [ABSTRACT FROM AUTHOR]

This paper presents a new hazard-consistent ground motion characterization of the Itoiz dam site, located in Northern Spain. Firstly, we propose a methodology with different approximation levels to the expected ground motion at the dam site. Secondly, we apply this methodology taking into account the particular characteristics of the site and of the dam. Hazard calculations were performed following the Probabilistic Seismic Hazard Assessment method using a logic tree, which accounts for different seismic source zonings and different ground-motion attenuation relationships. The study was done in terms of peak ground acceleration and several spectral accelerations of periods coinciding with the fundamental vibration periods of the dam. In order to estimate these ground motions we consider two different dam conditions: when the dam is empty ( T = 0.1 s) and when it is filled with water to its maximum capacity ( T = 0.22 s). Additionally, seismic hazard analysis is done for two return periods: 975 years, related to the project earthquake, and 4,975 years, identified with an extreme event. Soil conditions were also taken into account at the site of the dam. Through the proposed methodology we deal with different forms of characterizing ground motion at the study site. In a first step, we obtain the uniform hazard response spectra for the two return periods. In a second step, a disaggregation analysis is done in order to obtain the controlling earthquakes that can affect the dam. Subsequently, we characterize the ground motion at the dam site in terms of specific response spectra for target motions defined by the expected values SA ( T) of T = 0.1 and 0.22 s for the return periods of 975 and 4,975 years, respectively. Finally, synthetic acceleration time histories for earthquake events matching the controlling parameters are generated using the discrete wave-number method and subsequently analyzed. Because of the short relative distances between the controlling earthquakes and the dam site we considered finite sources in these computations. We conclude that directivity effects should be taken into account as an important variable in this kind of studies for ground motion characteristics. [ABSTRACT FROM AUTHOR]

This paper describes the outcome of the advanced seismic hazard and seismic risk estimates recently performed for the city of Sofia, based on the state-of-the-art of knowledge for this site. Some major results of the neo-deterministic, scenario-based, seismic hazard assessment approach (NDSHA) to the earthquake hazard assessment for the city of Sofia are considered. Further validations of the recently constructed synthetic strong motion database, containing site and seismic source-specific ground motion time histories are performed and discussed. Displacement and acceleration response spectra are considered. The elastic displacement response spectra and displacement demand are discussed with regard to earthquake magnitude, seismic source-to-site distance, seismic source mechanism, and local geological site conditions. The elastic response design spectrum from the standard pseudo-acceleration, versus natural period, T, format, converted to a capacity diagram in S − S format is discussed in the perspective of the Eurocode 8 provisions. A brief overview of the engineering applications of the seismic demand obtained making use of the NDSHA is supplied. Some applications of the outcome of NDSHA procedure for engineering purposes are shown. The obtained database of ground shaking waveforms and time-histories, computed for city of Sofia is used to: (1) extract maximum particle velocities; (2) calculate the space distribution of the horizontal strain factor Log ε; (3) estimate liquefaction susceptibility in terms of standard penetration test, N values, and initial over burden stress; (4) estimate damage index distribution; and (5) map the distribution of the expected pipe breaks and red-tagged buildings for given scenario earthquakes, etc. The theoretically obtained database, based on the simultaneous treatment of the data from many disciplines, contains data fully suitable for practical use. The proper use of this database can lead to a significant seismic vulnerability reduction and thus contributes to earthquake preparedness. [ABSTRACT FROM AUTHOR]

The paper is intended to summarize the most important instrumental data of direct relevance for engineering activities, obtained in connection with the strong Vrancea earthquakes of 4 March 1977, 30 August 1986, 30 May 1990, and 31 May 1990, and to point out some significant consequences and conclusions derived on this basis. Two main objectives of this analysis may be emphasized: (a) in-depth analysis of the radiation pattern; and (b) analysis of the spectral contents of ground motion in connection with the features of local conditions, and with the intention of assessing the relative importance of two main factors: source mechanism and long-distance wave propagation, versus features of local geological conditions. Some specific methodological developments used in this context may be mentioned: (a) use of a new approach to the quantification of ground motion intensity on the basis of instrumental (accelerographic) information; (b) analysis of radiation pattern in spectral and directivity terms; (c) parametric analysis of site-specific transfer functions for the local sequences of geological layers; and (d) a critical view on the outcome of post-earthquake survey techniques, keeping in view the implications of the spectral features of ground motion. The main results obtained are related to: (a) ground motion radiation features that have to be taken into account in connection with the data on the source mechanisms of the successive events dealt with; (b) expected spectral features of future strong ground motion at different sites; (c) methodological developments proposed for the assessment of local transfer functions; and (d) implications for microzonation activities. [ABSTRACT FROM AUTHOR]

The Project 'MAR VASTO' (Risk Management in Valparaíso/Manejo de Riesgos en Valparaíso), funded by BID/IADB (Banco InterAmericano de Desarrollo/InterAmerican Development Bank), has been managed by ENEA, with an Italian/Chilean joined partnership and the support of local institutions. Valparaíso tells the never-ending story of a tight interaction between society and environment and the city has been declared a Patrimony of Humanity by UNESCO since 2003. The main goals of the project have been to evaluate in the Valparaíso urban area the impact of main hazards (earthquake, tsunami, fire, and landslide), defining scenarios and maps on a geo-referenced GIS database. In particular, for earthquake hazard assessment the realistic modelling of ground motion is a very important base of knowledge for the preparation of groundshaking scenarios which serve as a valid and economic tool to be fruitfully used by civil engineers, supplying a particularly powerful tool for the prevention aspects of Civil Defense. When numerical modelling is successfully compared with records (as in the case of the Valparaíso, 1985 earthquake), the resulting synthetic seismograms permit the generation of groundshaking maps, based upon a set of possible scenario earthquakes. Where no recordings are available for the scenario event, synthetic signals can be used to estimate ground motion without having to wait for a strong earthquake to occur (pre-disaster microzonation). For the tsunami hazard, the available reports, [e.g., SHOA (1999) Carta de Inundacion por Tsunami para la bahia de Valparaíso, Chile, ], have been used as the reference documents for the hazard assessment for the Valparaíso site. The deep and detailed studies already carried out by SHOA have been complemented with (a) sets of parametric studies of the tsunamigenic potential of the 1985 and 1906 scenario earthquakes; and (b) analytical modelling of tsunami waveforms for different scenarios, in order to provide a complementary dataset to be used for the tsunami hazard assessment at Valparaíso. In addition, other targeted activities have been carried out, such as architectonic/urban planning studies/vulnerability evaluation for a pilot building stock in a historic area and a vulnerability analysis for three monumental churches. In this paper, a general description of the work is given, taking into account the in situ work that drove the suggestion of guidelines for mitigation actions. [ABSTRACT FROM AUTHOR]

The first part of the paper defines the terms and classifications common in earthquake prediction research and applications. This is followed by short reviews of major earthquake prediction programs initiated since World War II in several countries, for example the former USSR, China, Japan, the United States, and several European countries. It outlines the underlying expectations, concepts, and hypotheses, introduces the technologies and methodologies applied and some of the results obtained, which include both partial successes and failures. Emphasis is laid on discussing the scientific reasons why earthquake prediction research is so difficult and demanding and why the prospects are still so vague, at least as far as short-term and imminent predictions are concerned. However, classical probabilistic seismic hazard assessments, widely applied during the last few decades, have also clearly revealed their limitations. In their simple form, they are time-independent earthquake rupture forecasts based on the assumption of stable long-term recurrence of earthquakes in the seismotectonic areas under consideration. Therefore, during the last decade, earthquake prediction research and pilot applications have focused mainly on the development and rigorous testing of long and medium-term rupture forecast models in which event probabilities are conditioned by the occurrence of previous earthquakes, and on their integration into neo-deterministic approaches for improved time-variable seismic hazard assessment. The latter uses stress-renewal models that are calibrated for variations in the earthquake cycle as assessed on the basis of historical, paleoseismic, and other data, often complemented by multi-scale seismicity models, the use of pattern-recognition algorithms, and site-dependent strong-motion scenario modeling. International partnerships and a global infrastructure for comparative testing have recently been developed, for example the Collaboratory for the Study of Earthquake Predictability (CSEP) with test regions in California, Italy, Japan, New Zealand, and the Western Pacific. Algorithms and data bases are operated in a permanently learning and upgrading mode. Future perspectives and research requirements and the feasibility and possible problems encountered with the implementation of earthquake predictions in practice are briefly summarized. [ABSTRACT FROM AUTHOR]

It is an acquired result that, in order to enable realistic earthquake hazard assessment and reliable estimation of the ground motion response to an earthquake, three-dimensional velocity models have to be considered. In this paper we present a new analytical procedure for determining the seismic wavefield in a 3D anelastic model based on the combination of the ray theory with the modal summation method. The proposed procedure has been validated by considering the three-dimensional model of the Kanto basin (Japan) available in the literature. Three-dimensional simulations were performed for the 1990 Odawara earthquake. The results obtained were compared both with recorded signals and with simulations available in the literature for several stations located within the Kanto basin. Besides the advantage of being a useful tool for assessment of seismic hazard and seismic risk reduction, it is characterized by high efficiency, in fact, once the study region is identified and the 3D model is constructed, the computation, at each station, of the three components of the synthetic signal (displacement, velocity, and acceleration) takes less than 3 h on a 2 GHz CPU. [ABSTRACT FROM AUTHOR]

We present the basis for a method for estimating the return period of large and medium earthquakes that is independent of current deterministic and probabilistic approaches. The two standard techniques of seismic hazard assessment-probabilistic seismic hazard assessment (PSHA) and deterministic seismic hazard assessment (DSHA)-suffer from limited knowledge of seismic prehistory. A further weakness of PSHA is its requirement of homogeneous seismic activity within a seismic zone. Moreover, PSHA and DSHA were developed for seismically active areas and, thus, cannot reliably be used in areas of medium and low activity. In this paper we propose the combined use of geodetic strain rate data and the seismic moment data set determined for past seismic events. This combination represents a new and independent approach to estimation of future seismic activity. Using a modified version of Kostrov's (Phys Solid Earth 1:23-40, ) equation and the catalogue of seismic moments, the minimum return period of the strongest earthquakes of a source area is estimated. [ABSTRACT FROM AUTHOR]

Izmir, the third largest city and one of the major economic centers in Turkey, has more than three million residents and one-half million buildings. The city, located in a seismically active region in western Anatolia, was a subject of the 1997 RADIUS (Risk Assessment Tools for Diagnosis of Urban Areas against Seismic Disaster) project. In this paper, the seismic hazard of Izmir is investigated through probabilistic seismic hazard assessment. First, the seismic setting of Izmir is presented. Considering the statistics of earthquakes that took place in the region during the period 1900-2005, a simple seismic hazard model is used to facilitate the assessment. To account for modeling uncertainties associated with the values of seismicity parameters, a logic tree procedure is employed in carrying out the seismic hazard computations. The resulting weighted average seismic hazard, presented in terms of peak ground acceleration and associated probability of exceedence, could be considered the 'best estimate' of seismic hazard for Izmir. Accordingly, for a return period of 475 years, for rock sites, a PGA value of 0.34 g is calculated. This PGA hazard estimate is close to the current code-recommended design acceleration level for Izmir. [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]

The occurrence of the Algiers earthquake ( M 6.8) of May 21, 2003, has motivated the necessity to reassess the probabilistic seismic hazard of northern Algeria. The fact that this destructive earthquake took place in an area where there was no evidence of previous significant earthquakes, neither instrumental nor historical, strongly encourages us to review the seismic hazard map of this region. Recently, the probabilistic seismic hazard of northern Algeria was computed using the spatially smoothed seismicity methodology. The catalog used in the previous computation was updated for this review, and not only includes information until June 2003, but also considers a recent re-evaluation of several historical earthquakes. In this paper, the same methodology and seismicity models are utilized in an effort to compare this methodology against an improved and updated seismic catalog. The largest mean peak ground acceleration (PGA) values are obtained in northernmost Algeria, specifically in the central area of the Tell Atlas. These values are of the order of 0.48 g for a return period of 475 years. In the City of Algiers, the capital of Algeria, and approximately 50 km from the reported epicenter of this latest destructive earthquake, a new mean PGA value of 0.23 g is obtained for the same return period. This value is 0.07 g greater than that obtained in the previous computation. In general, we receive greater seismic hazard results in the surrounding area of Algiers, especially to the southwest. The main reason is not this recent earthquake by itself, but the significant increase in the mmax magnitude in the seismic source where the city and the epicenter are included. [ABSTRACT FROM AUTHOR]