Probabilistic seismic hazard analysis for spatially distributed infrastructure considering the correlation of spectral acceleration across spectral periods

2021 ◽  
pp. 875529302110582
Author(s):  
Ioanna Kavvada ◽  
Scott Moura ◽  
Arpad Horvath ◽  
Norman Abrahamson
Keyword(s):  
Seismic Hazard ◽  
San Francisco ◽  
Variance Reduction ◽  
Ease Of Use ◽  
Compact Set ◽  
Spectral Acceleration ◽  
Period Range ◽  
Simplified Approach ◽  
Spatially Distributed ◽  
Infrastructure Performance

Regional seismic hazard analyses are necessary to assess the infrastructure performance within a region and ensure that mitigation funds are utilized effectively by probabilistically considering the suite of potential earthquake events. This research aims to efficiently represent the regional seismic hazard through a compact set of seismic inputs in the form of spectral acceleration (SA) maps by considering the spatial cross-correlation of SA at a wide period range. The SA maps can then be used to probabilistically estimate the performance of a portfolio of spatially distributed structures with different fundamental periods. Efficient representation reduces the number of required SA maps to decrease the computational demands of the infrastructure performance analysis in the subsequent steps. The added dimension of the between-period spatial SA correlation exacerbates the challenge of effectively simulating and selecting a set of SA maps to reproduce the hazard curves particularly at long return periods. Two approaches are proposed to generate an optimal set of SA maps: (a) a simulation-based methodology that uses state-of-the-art variance reduction methods and (b) a simplified methodology that aims to increase the ease of use and reduce the computational demands of the simulation. The two approaches are implemented and compared using the city of San Francisco as a case study to illustrate their feasibility. The simplified approach increases the scalability of the methodology to larger study areas at the expense of reduced accuracy in terms of seismic hazard curve and SA correlation errors.

A Simplified Approach to Estimate Flow-Induced Vibrations on an Elbowed Piping System

2018 ◽  
Author(s):  
André Baramili ◽  
Ludovic Chatellier ◽  
Laurent David ◽  
Loïc Ancian
Keyword(s):  
Element Model ◽  
Numerical Approach ◽  
Piping System ◽  
Least Squares Regression ◽  
Flow Induced Vibration ◽  
Simplified Approach ◽  
Eddy Simulation ◽  
Spatially Distributed ◽  
Closed Water ◽  
Modeling Strategy

A mixed experimental and numerical approach was undertaken in order to develop a data-based model of the flow-induced vibration levels attained in a piping system containing a 90° elbow. A closed water loop was used to provide unsteady flow data as well as wall pressure and vibration measurements. In parallel, the unsteady water flow through the elbow was computed using an incompressible Large-Eddy Simulation (LES). Proper Orthogonal Decomposition (POD) and Partial Least Squares Regression (PLSR) were used in order to build a relationship between the flow properties and the resulting excitation. This relationship was then used to estimate the evolution of the spatially distributed loadings, which were finally applied to a finite element model of the piping structure. The results consisted of an estimation of the vibration levels. The estimated vibrations were then compared to measurements in order to validate the proposed modeling strategy.

Application of inelastic response spectra derived from seismic hazard spectral ordinates for Canada

1996 ◽  
Vol 23 (5) ◽  
pp. 1051-1063 ◽  
Author(s):  
J. L. Humar ◽  
M. A. Rahgozar
Keyword(s):  
Seismic Hazard ◽  
Response Spectra ◽  
Reduction Factor ◽  
Reliable Estimate ◽  
Spectral Acceleration ◽  
Hazard Maps ◽  
Uniform Hazard Spectra ◽  
Spectral Curves ◽  
Modification Factor ◽  
Recorded Data

The Geological Survey of Canada is currently producing a suite of new hazard maps for Canada. These maps take into account the additional recorded data obtained during the past 13 years, as well as the new geological and tectonic information that has recently become available. They provide elastic spectral acceleration values for a uniform probability of exceedance of 10% in 50 years. A method of using the uniform hazard spectral values to obtain design response spectral curves for different values of ductility is presented here. The method uses two spectral values obtained from the hazard maps, the peak spectral acceleration for the site and the spectral acceleration corresponding to a period of 0.5 s. Empirical expressions are developed to represent the design response spectra. It is shown that by using inelastic spectral accelerations rather than the elastic spectral values in association with a reduction factor, the new method provides a more reliable estimate of the design forces. Key words: uniform hazard spectra; inelastic spectra, seismic design forces, force modification factor, foundation factor, seismic hazard for Canada.

Seismic Hazard and Loss Analysis for Spatially Distributed Infrastructure in Christchurch, New Zealand

2016 ◽  
Vol 32 (2) ◽  
pp. 697-712 ◽  
Author(s):  
Hasan Manzour ◽  
Rachel A. Davidson ◽  
Nick Horspool ◽  
Linda K. Nozick
Keyword(s):  
New Zealand ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Regional Scale ◽  
Average Error ◽  
Loss Analysis ◽  
Spatially Distributed ◽  
Small Set ◽  
Computationally Intensive ◽  
Distributed Infrastructure

The new Extended Optimization-Based Probabilistic Scenario method produces a small set of probabilistic ground motion maps to represent the seismic hazard for analysis of spatially distributed infrastructure. We applied the method to Christchurch, New Zealand, including a sensitivity analysis of key user-specified parameters. A set of just 124 ground motion maps were able to match the hazard curves based on a million-year Monte Carlo simulation with no error at the four selected return periods, mean spatial correlation errors of 0.03, and average error in the residential loss exceedance curves of 2.1%. This enormous computational savings in the hazard has substantial implications for regional-scale, policy decisions affecting lifelines or building inventories since it can allow many more downstream analyses and/or doing them using more sophisticated, computationally intensive methods. The method is robust, offering many equally good solutions and it can be solved using free open source optimization solvers.

The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

2019 ◽  
Vol 36 (1) ◽  
pp. 5-41 ◽  
Author(s):  
Mark D. Petersen ◽  
Allison M. Shumway ◽  
Peter M. Powers ◽  
Charles S. Mueller ◽  
Morgan P. Moschetti ◽  
...  
Keyword(s):  
United States ◽  
Los Angeles ◽  
Seismic Hazard ◽  
San Francisco ◽  
Urban Areas ◽  
Salt Lake ◽  
Sedimentary Basins ◽  
Hazard Model ◽  
Eastern United States ◽  
Ground Shaking

During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated epistemic uncertainties and aleatory variabilities, and new soil amplification factors; (3) in the western United States (WUS), amplified shaking estimates of long-period ground motions at sites overlying deep sedimentary basins in the Los Angeles, San Francisco, Seattle, and Salt Lake City areas were incorporated; and (4) in the conterminous United States, seismic hazard is calculated for 22 periods (from 0.01 to 10 s) and 8 uniform VS30 maps (ranging from 1500 to 150 m/s). We also include a description of updated computer codes and modeling details. Results show increased ground shaking in many (but not all) locations across the CEUS (up to ~30%), as well as near the four urban areas overlying deep sedimentary basins in the WUS (up to ~50%). Due to population growth and these increased hazard estimates, more people live or work in areas of high or moderate seismic hazard than ever before, leading to higher risk of undesirable consequences from forecasted future ground shaking.

scholarly journals Estimation of peak ground acceleration and spectral acceleration for South India with local site effects: probabilistic approach

2009 ◽  
Vol 9 (3) ◽  
pp. 865-878 ◽  
Author(s):  
K. S. Vipin ◽  
P. Anbazhagan ◽  
T. G. Sitharam
Keyword(s):  
Seismic Hazard ◽  
Peak Ground Acceleration ◽  
South India ◽  
Hazard Analysis ◽  
Shear Zones ◽  
Spectral Acceleration ◽  
Ground Acceleration ◽  
Site Class ◽  
Probability Of Exceedance ◽  
Grid Points

Abstract. In this work an attempt has been made to evaluate the seismic hazard of South India (8.0° N–20° N; 72° E–88° E) based on the probabilistic seismic hazard analysis (PSHA). The earthquake data obtained from different sources were declustered to remove the dependent events. A total of 598 earthquakes of moment magnitude 4 and above were obtained from the study area after declustering, and were considered for further hazard analysis. The seismotectonic map of the study area was prepared by considering the faults, lineaments and the shear zones in the study area which are associated with earthquakes of magnitude 4 and above. For assessing the seismic hazard, the study area was divided into small grids of size 0.1°×0.1°, and the hazard parameters were calculated at the centre of each of these grid cells by considering all the seismic sources with in a radius of 300 km. Rock level peak horizontal acceleration (PHA) and spectral acceleration (SA) values at 1 s corresponding to 10% and 2% probability of exceedance in 50 years have been calculated for all the grid points. The contour maps showing the spatial variation of these values are presented here. Uniform hazard response spectrum (UHRS) at rock level for 5% damping and 10% and 2% probability of exceedance in 50 years were also developed for all the grid points. The peak ground acceleration (PGA) at surface level was calculated for the entire South India for four different site classes. These values can be used to find the PGA values at any site in South India based on site class at that location. Thus, this method can be viewed as a simplified method to evaluate the PGA values at any site in the study area.

scholarly journals Spatial Seismic Hazard Variation and Adaptive Sampling of Portfolio Location Uncertainty in Probabilistic Seismic Risk Analysis

2019 ◽  
Author(s):  
Christoph Scheingraber ◽  
Martin Käser
Keyword(s):  
Risk Analysis ◽  
Seismic Hazard ◽  
Seismic Risk ◽  
Adaptive Sampling ◽  
Variance Reduction ◽  
Loss Rate ◽  
Insurance Industry ◽  
Rate Variation ◽  
Seismic Risk Analysis ◽  
Location Uncertainty

Abstract. Probabilistic Seismic Risk Analysis is widely used in the insurance industry to model the likelihood and severity of losses to insured portfolios by earthquake events. Due to geocoding issues of address information, risk items are often only known to be located within an administrative geographical zone, but precise coordinates remain unknown to the modeler. In the first part of this paper, we analyze spatial seismic hazard and loss rate variation inside administrative geographical zones in western Indonesia. We find that the variation of hazard can vary strongly not only between different zones, but also between different return periods for a fixed zone. However, the spatial variation of loss rate displays a similar pattern as the variation of hazard, without depending on the return period. We build upon these results in the second part of this paper. In a recent work, we introduced a framework for stochastic treatment of portfolio location uncertainty. This results in the necessity to simulate ground motion on a high number of sampled geographical coordinates, which typically dominates the computational effort in Probabilistic Seismic Risk Analysis. We therefore propose a novel sampling scheme to improve the efficiency of stochastic portfolio location uncertainty treatment. Depending on risk item properties and measures of spatial loss rate variation, the scheme dynamically adapts the location sample size individually for insured risk items. We analyze the convergence and variance reduction of the scheme empirically. The results show that the scheme can improve the efficiency of the estimation of loss frequency curves.

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