Seismic Hazards and Water Supply Performance

This article describes seismic hazards, including fault rupture, liquefaction, landslides, and site amplification, using Los Angeles as a case study. Water supply simulation results are presented for a 7.8 M_W earthquake on the San Andreas Fault. Severe water losses are shown after 24 h, with nearly 2,700 locations of pipeline damage and a 66% decrease in normal water service. The water supply system was modeled with and without reservoirs that have been removed from service to meet water quality standards. The results show that opening the disconnected reservoirs immediately after a serious earthquake is an effective strategy for emergency response.     

Unconditional Reliability-Based Design of Tuned Liquid Column Dampers Under Stochastic Earthquake Load Considering System Parameters Uncertainties

The reliability-based design of tuned mass damper considering system parameters uncertainties is noteworthy. However, the same is not the case for liquid dampers. The present study deals with the reliability-based design of tuned liquid column dampers under random earthquake considering system parameters uncertainties. Using the conditional second-order information of response quantities, the total probability concept is applied to evaluate the unconditional failure probability which is subsequently used as the objective function to obtain the damping parameters. A numerical study elucidates the effect of system parameters uncertainties on the damper parameters optimization and safety of the structure.     

Stochastic Modeling of Earthquake Scenarios in Greater Tehran

Tehran, the capital of Iran, with millions of inhabitants, has been affected several times by historical and recent earthquakes that confirm the importance of seismic hazard assessment for the area. The main objective of this article is to present a probabilistic procedure to construct time series compatible with the source-path and site reflecting the influence of different magnitude events at different distances that may occur during a specified time period. A Monte Carlo approach is used to generate numerous synthetic catalogs for the evaluation of the probabilistic seismic hazard in greater Tehran over hard rock site for a return period of 475 years. The disaggregation of the seismic hazard is carried out to identify hazard-dominating events and to associate them with one or more specific faults, rather than a given distance. The stochastic finite-fault technique based on region specific seismic parameters is used to generate time series of earthquake scenario.     

Correlations Between Frequency Content Indicators of Strong Ground Motions and PGV

The frequency content of ground motions seems to be one of the most important parameters to explain the structural damage experienced during worldwide strong earthquakes. The frequency content of ground motions can be characterized by various stochastic and/or deterministic indicators: the frequency bandwidth indicator ? (Cartwright & Longuet-Higgins) related to the power spectral density function and, respectively, the control (corner) period T_c of the structural response spectra or the mean period T_M . Peak ground velocity (PGV) and the ratio PGA/PGV can be used as either damage potential parameters or frequency content indicators. A comparative analysis of stochastic and deterministic frequency content indicators and of PGV is applied to a set of 30 strong ground motion records having peak ground acceleration (PGA) from 0.2–0.8 g and recorded on 4 continents during the last 70 years.     

Stochastic Quantification of Soil-Shallow Foundation-Structure Interaction

This article highlights soil-structure interaction (SSI) effects on the seismic structural response accounting for uncertainties in the model parameters and input ground motions. A probabilistic Monte Carlo methodology was used to conduct approximately six million dynamic time-history simulations using an established rheological soil-shallow foundation-structure model. Considering the results yields outcomes that contradict prevailing views of the always beneficial role of SSI. In other words, the likelihood of having amplification in structural response due to SSI is large enough that it cannot be readily ignored. This research provides a significant first step towards reliability-based seismic design procedures incorporating foundation flexibility.     

Successive Earthquake-Tsunami Analysis to Develop Collapse Fragilities

Over the last half century, scientists and engineers have developed methods to better understand and mitigate the damage caused by tsunamis. According to U.S. Federal Emergency Management Agency (FEMA) P646, buildings in many regions, including the U.S. Pacific Northwest, will experience substantial ground shaking from an offshore earthquake that precedes a tsunami and then experience the tsunami forces themselves. Thus, both hazards should be considered in computing the damage and collapse risk to buildings. This article summarizes a basic approach to numerically consider the successive seismic and tsunami risk to buildings in near-field tsunami regions such as the U.S. Pacific Northwest.     

Derivation of New Equations for Prediction of Principal Ground-Motion Parameters using M5′ Algorithm

In this study, M5′ model tree is used to develop a model for prediction of peak time-domain strong ground motion parameters. The main advantages of model trees are that can be easily developed and their formulas are simple and understandable. Selected data from Pacific Earthquake Engineering Research Center (PEER) are used to train the proposed model. Earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms are used as input parameters. The developed M5′ based formulas are compared with those of well-known empirical and soft computing based models. The accuracy of the model is evaluated by statistical error parameters.     

Performance-Based Seismic Assessment of Superelastic Shape Memory Alloy-Reinforced Bridge Piers Considering Residual Deformations

The application of superelastic Shape Memory Alloy (SMA) reinforcement in plastic hinge regions of bridge piers has been proven to reduce the residual displacement after a strong shaking owing to its unique shape recovery characteristics; however, the maximum deformation of the piers could increase due to the relatively lower modulus of elasticity of SMA bars and lower hysteretic energy dissipation capacity. In this context, this article applies a recently formulated probabilistic performance-based seismic assessment methodology that considers both the maximum and the residual deformation simultaneously to evaluate the performance of SMA reinforced bridge piers.     

OBTAINING PROBABILISTIC ESTIMATES OF DISPLACEMENT ON A LANDSLIDE DURING FUTURE EARTHQUAKES

The assessment of earthquake triggered landslide hazard may be undertaken using both deterministic and probabilistic techniques. Probabilistic methods have been developed because much of the data can be considered as random variables where parameters such as the angle of internal friction and moisture content do not have a single fixed value but may assume any number of values across a range. This random variability can be modelled by a probability density function (PDF) which describes the relative likeli-hood that a random variable will assume a particular value. Instead of using just the average or expected value of an input parameter, the complete range of possible values can be used to estimate a range of possible outcomes. Thus the probability of a slope being unstable can be obtained rather than a single indicator of stability. Such proba-bilistic analyses allow for the incorporation of the likely variability of each parameter and therefore allow a more intimate assessment of slope stability to be derived. Utilising empirical relationships for calculating earthquake ground motions and associated slope displacement, an investigation was undertaken to identify the contribution that modern simulation techniques could make to the assessment of earthquake-triggered landslides. To achieve this, geotechnical and earthquake data obtained from a deep-seated landslide triggered during the M _w 7.0 Loma Prieta earthquake was used. By incorporating the variability of the geotechnical parameters and the uncertainty in earthquake location the model derived the probabilities associated with increasing amounts of slope displacement during future probable earthquakes. Analysis was undertaken for four of the principal fault segments in the San Francisco Bay area. These estimates were then combined with the occurrence probabilities of the earthquakes to provide temporal estimates of dis-placement for a 30 year period. Results indicated that a M _w 7.0 earthquake located on the Peninsula Segment of the San Andreas fault was most hazardous with a 11% chance of minor slope displacement (≥0.10 m) and a 6% chance of moderate slope displacement (≥0.30 m) within the next 30 years.