scholarly journals The Effect of Alternative Seismotectonic Models on PSHA Results – a Sensitivity Study for the Case of Israel

2017 ◽  
Author(s):  
Matan Avital ◽  
Michael Davis ◽  
Ory Dor ◽  
Ronnie Kamai
Keyword(s):  
Epistemic Uncertainty ◽  
Near Field ◽  
Uncertainty Propagation ◽  
Slip Rate ◽  
Parametric Uncertainty ◽  
Sensitivity Study ◽  
Prediction Equation ◽  
Fault System ◽  
Model Parameters ◽  
Alternative Source

Abstract. We present a full PSHA sensitivity analysis for two sites in southern Israel – one in the near-field of a major fault system and one farther away. The PSHA analysis is conducted for alternative source representations, using alternative model parameters for the main seismic sources, such as slip-rate and Mmax, among others. The analysis also considers the effect of the Ground-Motion Prediction Equation (GMPE) on the hazard results. In this way, the two types of epistemic uncertainty – modelling uncertainty and parametric uncertainty are treated and addressed. We quantify the uncertainty propagation by testing its influence of the final calculated hazard, such that the controlling knowledge gaps are identified and can be treated in future studies. We find that current practice in Israel, as represented by the most current version of the building code grossly underestimates the hazard, due to a combination of factors, including source definitions as well as the GMPE used for analysis.

scholarly journals The effect of alternative seismotectonic models on PSHA results – a sensitivity study for two sites in Israel

2018 ◽  
Vol 18 (2) ◽  
pp. 499-514 ◽  
Author(s):  
Matan Avital ◽  
Ronnie Kamai ◽  
Michael Davis ◽  
Ory Dor
Keyword(s):  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Near Field ◽  
Slip Rate ◽  
Parametric Uncertainty ◽  
Sensitivity Study ◽  
Fault System ◽  
Model Parameters ◽  
Return Periods ◽  
Alternative Source

Abstract. We present a full probabilistic seismic hazard analysis (PSHA) sensitivity analysis for two sites in southern Israel – one in the near field of a major fault system and one farther away. The PSHA analysis is conducted for alternative source representations, using alternative model parameters for the main seismic sources, such as slip rate and Mmax, among others. The analysis also considers the effect of the ground motion prediction equation (GMPE) on the hazard results. In this way, the two types of epistemic uncertainty – modelling uncertainty and parametric uncertainty – are treated and addressed. We quantify the uncertainty propagation by testing its influence on the final calculated hazard, such that the controlling knowledge gaps are identified and can be treated in future studies. We find that current practice in Israel, as represented by the current version of the building code, grossly underestimates the hazard, by approximately 40 % in short return periods (e.g. 10 % in 50 years) and by as much as 150 % in long return periods (e.g. 10E−5). The analysis shows that this underestimation is most probably due to a combination of factors, including source definitions as well as the GMPE used for analysis.

Quantifying the Epistemic Uncertainty in the Probabilistic Seismic Hazard from Two Major Faults in Western Nevada

2018 ◽  
Vol 34 (2) ◽  
pp. 549-568 ◽  
Author(s):  
John G. Anderson
Keyword(s):  
Distribution Function ◽  
Lognormal Distribution ◽  
Epistemic Uncertainty ◽  
Hanging Wall ◽  
Slip Rate ◽  
Prediction Equation ◽  
Exceedance Probability ◽  
Normal Faults ◽  
Logic Tree ◽  
Tree Distribution

The probabilistic seismic hazards in the larger cities of western Nevada are dominated by the Mount Rose and Carson Range faults. These are normal faults; Reno and Carson City are on the hanging wall. This paper finds the sensitivity of the hazard posed by these faults to epistemic uncertainty of dip, slip rate, magnitude, and choice of ground motion prediction equation (GMPE) for an earthquake that ruptures the length of each fault. SA(0.01 s) with exceedance probability of 2% in 50 years was determined for each branch of a logic tree for those properties. This paper uses tools of probability theory to characterize this logic tree distribution with a lognormal distribution function, and to suggest an estimate of uncertainty in the mean hazard. In this case, which should not be considered general, on the hanging wall, the uncertainties in fault dip and the choice of the GMPE are the dominant contribution to the standard deviation of the lognormal distribution function. Elsewhere nearby, uncertainties in fault slip rate dominate, while at larger distances uncertainties in the magnitude dominate.

scholarly journals Modeling Bacterial Regrowth and Trihalomethane Formation in Water Distribution Systems

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 463
Author(s):  
Gopinathan R. Abhijith ◽  
Leonid Kadinski ◽  
Avi Ostfeld
Keyword(s):  
Distribution Systems ◽  
Water Distribution ◽  
Mechanistic Model ◽  
Water Distribution Systems ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Growth Rate Constant ◽  
Model Parameters ◽  
Bacterial Regrowth ◽  
The Impact

The formation of bacterial regrowth and disinfection by-products is ubiquitous in chlorinated water distribution systems (WDSs) operated with organic loads. A generic, easy-to-use mechanistic model describing the fundamental processes governing the interrelationship between chlorine, total organic carbon (TOC), and bacteria to analyze the spatiotemporal water quality variations in WDSs was developed using EPANET-MSX. The representation of multispecies reactions was simplified to minimize the interdependent model parameters. The physicochemical/biological processes that cannot be experimentally determined were neglected. The effects of source water characteristics and water residence time on controlling bacterial regrowth and Trihalomethane (THM) formation in two well-tested systems under chlorinated and non-chlorinated conditions were analyzed by applying the model. The results established that a 100% increase in the free chlorine concentration and a 50% reduction in the TOC at the source effectuated a 5.87 log scale decrement in the bacteriological activity at the expense of a 60% increase in THM formation. The sensitivity study showed the impact of the operating conditions and the network characteristics in determining parameter sensitivities to model outputs. The maximum specific growth rate constant for bulk phase bacteria was found to be the most sensitive parameter to the predicted bacterial regrowth.

scholarly journals Stochastic and epistemic uncertainty propagation in LCA

2013 ◽  
Vol 18 (7) ◽  
pp. 1393-1403 ◽  
Author(s):  
Julie Clavreul ◽  
Dominique Guyonnet ◽  
Davide Tonini ◽  
Thomas H. Christensen
Keyword(s):  
Epistemic Uncertainty ◽  
Uncertainty Propagation

Comparative Analysis of Methodologies for Uncertainty Propagation and Quantification

2017 ◽  
Author(s):  
Alessandra Cuneo ◽  
Alberto Traverso ◽  
Shahrokh Shahpar
Keyword(s):  
Engineering Design ◽  
Polynomial Chaos ◽  
Epistemic Uncertainty ◽  
Uncertainty Propagation ◽  
Computational Cost ◽  
Computational Effort ◽  
Optimization Under Uncertainty ◽  
Design Parameters ◽  
Test Case ◽  
Aleatory And Epistemic Uncertainty

In engineering design, uncertainty is inevitable and can cause a significant deviation in the performance of a system. Uncertainty in input parameters can be categorized into two groups: aleatory and epistemic uncertainty. The work presented here is focused on aleatory uncertainty, which can cause natural, unpredictable and uncontrollable variations in performance of the system under study. Such uncertainty can be quantified using statistical methods, but the main obstacle is often the computational cost, because the representative model is typically highly non-linear and complex. Therefore, it is necessary to have a robust tool that can perform the uncertainty propagation with as few evaluations as possible. In the last few years, different methodologies for uncertainty propagation and quantification have been proposed. The focus of this study is to evaluate four different methods to demonstrate strengths and weaknesses of each approach. The first method considered is Monte Carlo simulation, a sampling method that can give high accuracy but needs a relatively large computational effort. The second method is Polynomial Chaos, an approximated method where the probabilistic parameters of the response function are modelled with orthogonal polynomials. The third method considered is Mid-range Approximation Method. This approach is based on the assembly of multiple meta-models into one model to perform optimization under uncertainty. The fourth method is the application of the first two methods not directly to the model but to a response surface representing the model of the simulation, to decrease computational cost. All these methods have been applied to a set of analytical test functions and engineering test cases. Relevant aspects of the engineering design and analysis such as high number of stochastic variables and optimised design problem with and without stochastic design parameters were assessed. Polynomial Chaos emerges as the most promising methodology, and was then applied to a turbomachinery test case based on a thermal analysis of a high-pressure turbine disk.

scholarly journals Empirical Relationship for Assessing the Near-Field Horizontal Coseismic Displacement Using GPS Seismology Data

2021 ◽  
Vol 60 (1) ◽  
pp. 31-50
Author(s):  
Ryad Darawcheh ◽  
Riad Al Ghazzi ◽  
Mohamad Khir Abdul-wahed
Keyword(s):  
Near Field ◽  
Empirical Relationship ◽  
Active Faults ◽  
Historical Earthquakes ◽  
Dead Sea ◽  
Fault System ◽  
Coseismic Displacement ◽  
Data Set ◽  
Earthquake Parameters ◽  
Gps Station

In this research, a data set of horizontal GPS coseismic displacement in the near-field has been assembled around the world in order to investigate a potential relationship between the displacement and the earthquake parameters. Regression analyses have been applied to the data of 120 interplate earthquakes having the magnitude (Mw 4.8-9.2). An empirical relationship for prediction near-field horizontal GPS coseismic displacement as a function of moment magnitude and the distance between hypocenter and near field GPS station has been established using the multi regression analysis. The obtained relationship allows assessing the coseismic displacements associated with some large historical earthquakes occurred along the Dead Sea fault system. Such a fair relationship could be useful for assessing the coseismic displacement at any point around the active faults.

scholarly journals Bayesian rock physics inversion: application to CO2 storage monitoring

Geophysics ◽  
2021 ◽  
pp. 1-73
Author(s):  
Bastien Dupuy ◽  
Anouar Romdhane ◽  
Pierre-Louis Nordmann ◽  
Peder Eliasson ◽  
Joonsang Park
Keyword(s):  
Joint Inversion ◽  
Co2 Storage ◽  
Rock Physics ◽  
Model Space ◽  
Real Data ◽  
Sensitivity Study ◽  
Model Parameters ◽  
Reservoir Properties ◽  
Upward Migration ◽  
Before And After

Risk assessment of CO2 storage requires the use of geophysical monitoring techniques to quantify changes in selected reservoir properties such as CO2 saturation, pore pressure and porosity. Conformance monitoring and associated decision-making rest upon the quantified properties derived from geophysical data, with uncertainty assessment. A general framework combining seismic and controlled source electromagnetic inversions with rock physics inversion is proposed with fully Bayesian formulations for proper quantification of uncertainty. The Bayesian rock physics inversion rests upon two stages. First, a search stage consists in exploring the model space and deriving models with associated probability density function (PDF). Second, an appraisal or importance sampling stage is used as a "correction" step to ensure that the full model space is explored and that the estimated posterior PDF can be used to derive quantities like marginal probability densities. Both steps are based on the neighbourhood algorithm. The approach does not require any linearization of the rock physics model or assumption about the model parameters distribution. After describing the CO2 storage context, the available data at the Sleipner field before and after CO2 injection (baseline and monitor), and the rock physics models, we perform an extended sensitivity study. We show that prior information is crucial, especially in the monitor case. We demonstrate that joint inversion of seismic and CSEM data is also key to quantify CO2 saturations properly. We finally apply the full inversion strategy to real data from Sleipner. We obtain rock frame moduli, porosity, saturation and patchiness exponent distributions and associated uncertainties along a 1D profile before and after injection. The results are consistent with geology knowledge and reservoir simulations, i.e., that the CO2 saturations are larger under the caprock confirming the CO2 upward migration by buoyancy effect. The estimates of patchiness exponent have a larger uncertainty, suggesting semi-patchy mixing behaviour.

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