F. Jalayer

F. Jalayer
University College London | UCL · Institute for Risk and Disaster Reduction

Doctor of Philosophy

About

148
Publications
77,226
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Introduction
My research focuses on probabilistic methods and computational tools for risk modelling and disaster risk reduction. I am interested in numerical modelling of cascading phenomena and multi-risk assessment, involving treatment of uncertainties and consideration of time-dependent factors and drivers. I am increasingly interested in risk modelling considering the societal context and the complex interactions between human, nature, and the built environment.

Publications

Publications (148)
Article
Quantifying the impact of modelling uncertainty on seismic performance assessment of existing buildings is non-trivial when considering the partial information available on material properties, construction details, and the uncertainty in the capacity models. This task is further complicated when uncertainty related to ground motion representation...
Article
Full-text available
The uncertainty in the concrete compressive strength is one of the most challenging issues in safety checking of existing reinforced concrete (RC) buildings. The concrete compressive strength used in the assessment can highly influence the vulnerability results and thus the retrofit strategies. The need to use less expensive and less invasive in si...
Chapter
The uncertainty in the concrete compressive strength is one of the most challenging issues in the seismic assessment of an existing RC building. This works characterizes the compressive concrete strength based on both in-situ destructive and non-destructive tests. A large set of data including (destructive) core tests and SONREB (rebound number S a...
Article
Full-text available
The present work proposes a simulation-based Bayesian method for parameter estimation and fragility model selection for mutually exclusive and collectively exhaustive (MECE) damage states. This method uses an adaptive Markov chain Monte Carlo simulation (MCMC) based on likelihood estimation using point-wise intensity values. It identifies the simpl...
Article
Full-text available
The epidemic-type aftershock sequence (ETAS) model provides an effective tool for predicting the spatio-temporal evolution of aftershock clustering in short-term. Based on this model, a fully probabilistic procedure was previously proposed by the first two authors for providing spatio-temporal predictions of aftershock occurrence in a prescribed fo...
Article
The reliable forecasting of seismic sequences following a mainshock has practical implications because effective post-event response is crucial in earthquake-stricken regions, aftershocks can progressively cause increased damage, and compound economic losses. In the South Iceland Seismic Zone (SISZ), one of two large transform zones in Iceland wher...
Conference Paper
Assessment of analytical structural fragility for existing buildings is one of the fundamental steps in modern performance-based design and assessment. One main feature distinguishing the assessment of existing buildings is the uncertainty in determining the structural modeling parameters. This work employs two different sampling techniques (i.e. S...
Conference Paper
Full-text available
Considering uncertainties related to record-to-record variability together with modeling uncertainties is not a trivial task. Lacking renewal properties with the occurrence of each earthquake, limit state excursion due to modelling uncertainties may not be Poissonian. Modelling uncertainties can be propagated by applying the fragility concept only...
Conference Paper
Full-text available
The suitability of a ground-motion intensity measure (IM) is expressed through its efficiency and sufficiency. A sufficient IM is one that renders the estimation of demand for all intensity levels independent of all other ground motion parameters. The Relative Sufficiency Measure (RSM), has been proposed previously based on information theory conce...
Conference Paper
Full-text available
The spatio-temporal evolution of aftershock clustering in short-term can be seen effectively through the epidemic-type aftershock sequence (ETAS) model. A Bayesian and fully simulation-based workflow was previously proposed by the authors for providing spatio-temporal predictions of aftershock occurrence in a prescribed forecasting time interval (i...
Conference Paper
Full-text available
Probabilistic Seismic Hazard Analysis (PSHA) encompasses quantitative estimation of seismic hazard at a site by considering all plausible earthquake scenarios using different models and assumptions. The outcome of a PSHA is often reported as the mean rate of exceeding a specific ground motion intensity measure at a given site, as well as the unifor...
Preprint
Full-text available
The epidemic-type aftershock sequence (ETAS) model provides an effective tool for predicting the spatio-temporal evolution of aftershock clustering in short-term. Based on this model, a fully probabilistic procedure was previously proposed by the first two authors for providing spatio-temporal predictions of aftershock occurrence in a prescribed fo...
Conference Paper
Full-text available
Methodology: A fragility model expresses the probability of exceeding certain damage levels for a given level of intensity for a specific class of buildings or infrastructure. An empirical tsunami fragility curve for a given damage level is derived based on observed pairs of data for the tsunami intensity measure and the corresponding damage level....
Conference Paper
Full-text available
Methodology: Induced earthquakes have peculiar characteristics such as, relatively shallow depths, small magnitude, correlation with field operations, non-GR recurrence law, and eventually non-homogenous Poisson recurrence time. Indeed, induced seismicity tends to cluster in limited volumes near the wells where field operations (e.g., fluids inject...
Article
Full-text available
Forecasting the spatio-temporal occurrence of events is at the core of Operational Earthquake Forecasting, which is of great interest for risk management, particularly during ongoing seismic sequences. Epidemic type aftershock sequence (ETAS) models are powerful tools to estimate the occurrence of events during earthquake sequences. In this context...
Article
Full-text available
Tsunamis constitute a significant hazard for European coastal populations, and the impact of tsunami events worldwide can extend well beyond the coastal regions directly affected. Understanding the complex mechanisms of tsunami generation, propagation, and inundation, as well as managing the tsunami risk, requires multidisciplinary research and inf...
Preprint
Full-text available
The present work proposes a simulation-based Bayesian method for parameter estimation and fragility 10 model selection for mutually exclusive, and collectively exhaustive (MECE) damage states. This method uses adaptive Markov chain Monte Carlo simulation (MCMC) based on likelihood estimation using point-wise intensity values. It identifies the simp...
Article
Full-text available
Very large tsunamis are associated with low probabilities of occurrence. In many parts of the world, these events have usually occurred in a distant time in the past. As a result, there is low risk perception and a lack of collective memories, making tsunami risk communication both challenging and complex. Furthermore, immense challenges lie ahead...
Article
Full-text available
The Italian code requires spectrum compatibility with mean spectrum for a suite of accelerograms selected for time-history analysis. Although these requirements define minimum acceptability criteria, it is likely that code-based non-linear dynamic analysis is going to be done based on limited number of records. Performance-based safety-checking pro...
Conference Paper
Full-text available
Iceland is the most seismically active region in northern Europe. The largest earthquakes in Iceland occur within the two transform fault zones in the country, the more populous of which is the South Iceland Seismic Zone (SISZ). Intense aftershock sequences followed the two largest and recent earthquakes in SISZ and Reykjanes Peninsula Oblique Rift...
Conference Paper
Full-text available
Quantitative safety-checking is an essential part of performance-based design and retrofit of new and existing construction. The intensity-based Demand and Capacity Factor Design (DCFD) is a practical closed-form analytical safety-checking format, derived based on a set of simplifying assumptions that lends itself quite well to visual interpretatio...
Conference Paper
Full-text available
Over the last decade, earthquake forecasting research has shown that when properly applied, it is becoming increasingly more feasible to forecast the temporal and spatial progression of seismic sequences i.e., aftershocks triggered after a strong earthquake mainshock. This has practical importance because the aftershocks can progressively increase...
Article
Full-text available
Reliable seismic hazard analyses are crucial to mitigate seismic risk. When dealing with induced seismicity the standard Probabilistic Seismic Hazard Analysis (PSHA) has to be modified because of the peculiar characteristics of the induced events. In particular, the relative shallow depths, small magnitude, a correlation with field operations, and...
Conference Paper
Full-text available
On Sunday November 12, 2017, at 18:18:16 UTC, (21:48:16 local time), a strong earthquake with Mw7.3 occurred in western Iran in the border region between Iran and Iraq in vicinity of the Sarpol-e Zahab town. Unfortunately, this catastrophic seismic event caused 572 causalities, thousands of injured and vast amounts of damage to the buildings, house...
Article
Full-text available
Tsunamis are unpredictable and infrequent but potentially large impact natural disasters. To prepare, mitigate and prevent losses from tsunamis, probabilistic hazard and risk analysis methods have been developed and have proved useful. However, large gaps and uncertainties still exist and many steps in the assessment methods lack information, theor...
Conference Paper
Full-text available
The uncertainty in the concrete compressive strength is one of the most challenging issues in the seismic assessment of an existing RC building. This works characterizes the compressive concrete strength based on both in-situ destructive and non-destructive tests. A large set of data including (destructive) core tests and SONREB (rebound number S a...
Conference Paper
Full-text available
Italian code provides the option for non-linear time-history analysis for the multi-degree-of-freedom (MDOF) structures (NTC). A non-linear time-history analysis procedure known as “Cloud Analysis” employs the structur-al response to a suite of un-scaled ground motion records. Cloud Analysis results can be directly implemented in established proced...
Conference Paper
Full-text available
Seismic risk in the context of performance-based earthquake engineering can be represented in terms of the mean annual rate of exceeding a prescribed performance level. In such context, a record-and structure-specific scalar parameter or a low-dimensional vector of parameters known as the ground motion Intensity Measure (IM) is usually adopted to p...
Article
Full-text available
Recent earthquakes have exposed the vulnerability of existing buildings; this is demonstrated by damage incurred after moderate-to-high magnitude earthquakes. This stresses the need to exploit available data from different sources to develop reliable seismic risk components. As far as it regards empirical fragility assessment, accurate estimation o...
Article
In performance-based earthquake engineering, the suitability of an intensity measure (IM) is expressed through its efficiency and sufficiency. An efficient IM leads to a small record-to-record variability in the estimation of demand given seismic intensity. A sufficient IM is one that renders the estimation of demand for all intensity levels indepe...
Conference Paper
Full-text available
The Method: Quantifying the impact of modelling uncertainty on the seismic performance assessment is a crucial issue for existing buildings, considering the partial information available related to material properties, construction details and the uncertainty in the capacity models. It has been proved that the effect of structural modelling uncerta...
Article
Quantitative safety checking is an essential part of performance-based design and ret-rofit of new and existing construction. The intensity-based demand and capacity factor design (DCFD) is a practical closed-form safety-checking format that lends itself quite well to visual interpretation. Adopting the critical demand to capacity ratio as a global...
Article
Modelling uncertainty can significantly affect the structural seismic reliability assessment. However, the limit state excursion due to this type of uncertainty may not be described by a Poisson process as it lacks renewal properties with the occurrence of each earthquake event. Furthermore, considering uncertainties related to ground motion repres...
Article
Full-text available
Flood risk maps for the built environment can be obtained by integrating geospatial information on hazard, vulnerability and exposure. They provide precious support for strategic urban planning and decision-making. These maps, generated in a probabilistic framework, can consider various sources of uncertainty in the flood risk assessment such as th...
Article
Postearthquake reconnaissance and recent research on seismic risk analysis have shown that nonductile concrete frame structures are much more susceptible to collapse than modern code-conforming frames. The performance-based assessment paradigm has been a persistent research theme over the last decade within the earthquake engineering community in o...
Conference Paper
Full-text available
The original N2 method for reasonably regular buildings oscillating predominantly in a single mode envisioned a two-stage analysis, where the first stage involved the non-linear static analysis of the MDOF system using alternative monotonically increasing lateral load patterns and the second stage involved the non-linear time-history analysis of th...
Conference Paper
Full-text available
Measuring the incomplete knowledge of the structural properties in as-built conditions is a formidable challenge in the performance-based seismic assessment of existing reinforced concrete (RC) buildings. Two basic sources of structural modeling uncertainties, which can directly affect the component demand and capacities and even influence the even...
Conference Paper
Evaluation of the uncertainty related to concrete compressive strength is one of the important aspects in the seismic assessment of an existing RC building. This works aims to characterize the compressive concrete strength based on both in-situ destructive and non-destructive test measurements. A large database of the (destructive) core tests and S...
Conference Paper
Shake maps are useful tools for spatial mapping of the ground shaking for a given earthquake event. They are often used for calculating the empirical fragilities by associating the ground shaking level at a given building's location to the observed damage at that location. Alternatively, the ground shaking can be mapped for a given earthquake event...
Article
Full-text available
Probabilistic Seismic Hazard Analysis (PSHA) encompasses quantitative estimation of seismic hazard at a site by considering all plausible earthquake scenarios. The outcome of a PSHA is often reported as the mean rate of exceeding a specific ground motion intensity measure at a given site. This study attempts to perform PSHA for the western area of...
Conference Paper
Full-text available
Modeling parameter uncertainty can affect significantly the structural seismic reliability assessment. However, this type of uncertainty may not be described by a Poisson process as it lacks renewal properties with the occurrence of each earthquake event. Furthermore, considering uncertainties related to ground motion representation by employing as...
Conference Paper
Full-text available
The first days elapsed after the occurrence of an earthquake and its triggered aftershocks are crucial in terms of emergency decision-making. To this end, the adopted novel and fully-probabilistic procedure succeeds in providing spatio-temporal predictions of aftershock occur-rence in a prescribed forecasting time interval (in the order of hours or...
Conference Paper
Full-text available
Modeling parameter uncertainty can affect significantly the structural seismic reliability assessment. However, this type of uncertainty may not be described by a Poisson process as it lacks renewal properties with the occurrence of each earthquake event. Furthermore, considering uncertainties related to ground motion representation by employing as...
Conference Paper
Full-text available
Assessment of the long-term risk profile considering the triggered seismic sequence is rendered complicated by the short-term clustering of aftershock events following the main event and the increased potential for damage accumulation. The assessment of long-term seismic risk profile for the main seismic events is based on the renewal of the struct...
Conference Paper
Significant structural and non-structural damage suffered by residential buildings due to recent earthquakes worldwide provide a sad testimony to the vulnerability of the existing building stock. This evidence stresses the need to develop accurate seismic vulnerability assessment tools in the service of strategic planning and applicable at a territ...
Conference Paper
Full-text available
Incremental dynamic analysis (IDA) is the most frequently used non-linear dynamic analysis procedure for seismic fragility assessment. Nevertheless, its implementation involves complications such as heavy computational burden and potential bias in the results due to excessive scaling of the ground motion records. Cloud Analysis is an alternative no...
Conference Paper
Full-text available
The Probabilistic Seismic Hazard Analysis (PSHA) is performed for the western area of the city Naples (southern Italy) by employing the database of individual seismo-genic sources (DISS3.2) and parametric catalogue of Italian earthquakes (CPTI15). Seismogenic models include the individual seismogenic faults responsible for generating major earthqua...
Conference Paper
Full-text available
Recent earthquakes around the world and in Italy showed the seismic vulnerability of the existing building stock. This evidence stresses the need to develop accurate seismic fragility tools, to be applied at territorial scale. Herein, seismic vulnerability curves for existing masonry buildings are developed, based on damage assessment carried out t...
Article
Full-text available
Delineation of flood risk hotspots can be considered as one of the first steps in an integrated methodology for urban flood risk management and mitigation. This paper presents a step-by-step methodology in a GIS-based framework for identifying flooding risk hotspots for residential buildings. This is done by overlaying a map of potentially flood-pr...
Article
Full-text available
Incremental dynamic analysis (IDA) leads to curves expressed in terms of structural response versus intensity, commonly known as the IDA curves. It is known that implementation of IDA usually involves significant computational effort and most often significant scaling of the original records to various intensity levels. Employing as the performance...
Chapter
Full-text available
ABSTRACT: Incremental dynamic analysis (IDA) is a procedure in which a structure is subjected to a suite of ground mo-tion records, scaled to multiple levels of intensity and leading to corresponding curves of response versus intensity. Howev-er, implementation of IDA usually involves a significant computational effort. In this work, a simple and e...
Chapter
Incremental dynamic analysis (IDA) is a procedure in which a structure is subjected to a suite of ground motion records, scaled to multiple levels of intensity and leading to corresponding curves of response versus intensity. However, implementation of IDA usually involves a significant computational effort. In this work, a simple and efficient sol...
Conference Paper
In different high seismic regions around the world, post-earthquake reconnaissance has shown that nonductile concrete frame structures are much more susceptible to collapse than modern code-conforming frames. Therefore, for this type of structures, it is necessary to accurately model materials and members to capture the flexure, shear, and flexure-...
Article
A probabilistic method is proposed for conducting groundwater-related hazard assessments that are useful for the risk management of deep excavations in saturated soils in urban areas. The design of deep excavations, construction procedures and execution methods aimed at realizing underground infrastructure are characterized by major uncertainties r...
Article
Full-text available
In the immediate aftermath of a strong earthquake and in the presence of an ongoing aftershock sequence, scientific advisories in terms of seismicity forecasts play quite a crucial role in emergency decision-making and risk mitigation. Epidemic Type Aftershock Sequence (ETAS) models are frequently used for forecasting the spatio-temporal evolution...
Conference Paper
Full-text available
In different high seismic regions around the world, many nonductile existing reinforced concrete frame buildings, built without adequate seismic detailing requirements, have been damaged or collapsed after past earthquakes. These concrete frame buildings are much more susceptible to collapse than modern code-conforming frames. Therefore, for this t...
Article
Full-text available
The frequency and severity of natural catastrophes have increased significantly over the last few years, with countries around the world having to face huge economic and human losses. Italy in particular is very seismic-prone, being located in the precise area of convergence between the African and Eurasian lithospheric plates. In addition, most Ita...
Conference Paper
Full-text available
Quantifying the impact of modelling uncertainty on the seismic performance assessment is a crucial issue for existing buildings, considering the partial information available related to material properties, construction details and the uncertainty in the capacity models. The effect of structural modelling uncertainties on the seismic performance of...
Conference Paper
Full-text available
Recent devastating earthquakes around the world have shown the vulnerability and deficien-cies of existing reinforced concrete (RC) frame structures. In particular, recent research on seismic risk analysis have highlighted that nonductile concrete frame structures are much more susceptible to collapse than modern code-conforming frames. Therefore,...
Article
It is desirable that nonlinear dynamic analyses for structural fragility assessment are performed using un-scaled ground motions. The wide-spread use of a simple dynamic analysis procedure known as Cloud Analysis, which employs un-scaled records and linear regression, has been impeded by its alleged inaccuracies. This paper investigates fragility a...
Conference Paper
A wide area around the town of Naples is mantled by shallow unsaturated volcanoclastic soils that are highly susceptible to fast rainfall-induced flow-like landslides. Some casualties and huge damage recorded in the last twenty years testify the serious threat posed by such events. Due to the impact of these phenomena, the local research community...
Conference Paper
Full-text available
In the immediate aftermath of a strong earthquake, the road networks play a crucial role in rescue and recovery operations. The damaged infrastructure may lose their transitability (fully or partially) leading to disruption of road links. The consequences in most cases go beyond the disruption of the road links. In fact, the disruption of a road li...
Conference Paper
Full-text available
Cloud Analysis is based on simple regression in the logarithmic space of structural response versus seismic intensity for a set of registered records. This method is particularly efficient since it involves non-linear analysis of the structure subjected to a set of un-scaled ground motion time-histories. The simplicity of its underlying formulation...
Conference Paper
Full-text available
A rational evaluation of the seismic risk of urban areas cannot neglect the variability of the ground motion due to site amplification and the induced effects, such as soil liquefaction and slope stability. In this framework, the microzonation maps certainly represent the most adequate tool to account for this element in the seismic risk and for pl...
Article
Full-text available
In an attempt to do a back analysis of the damages caused to a nineteenth century masonry structure due to the October 2009 flash flood/debris flow event in Scaletta Zanclea, the flood discharge hydrograph is reconstructed in the ungauged conditions. The hydrograph for the solid discharge is then estimated by scaling up the liquid volume to the est...
Article
Calculating the limit state (LS) exceedance probability for a structure considering the main seismic event and the triggered aftershocks (AS) is complicated both by the time-dependent rate of aftershock occurrence and also by the cumulative damage caused by the sequence of events. Taking advantage of a methodology developed previously by the author...
Article
Full-text available
The majority of bridge infrastructures in Italy were built in the 1960s and ‘70s without any specific seismic provision being made. As a consequence, it is expected that these bridges would be highly vulnerable if subjected to a significant seismic event. Given this background, it is natural that the rapid and accurate assessment of economic losses...
Article
Full-text available
In an attempt to conduct a back analysis of the damage caused to a 19th century masonry structure due to the October 2009 flash flood/debris flow event in Scaletta Zanclea, a flood discharge hydrograph is reconstructed in the ungauged conditions. The hydrograph for the solid discharge is then estimated by scaling up the liquid volume to the estimat...
Article
Demand and Capacity Factor Design (DCFD) is a probability-based safety-checking format for performance-based seismic design and assessment of structures. Inspired from the original DCFD formulation for seismic excitation, this work proposes a similar performance-based safety-checking format for flooding, adopting the flood height as the intensity m...