Zehra Cagnan

A Local Ground-Motion Predictive Model for Turkey, and Its Comparison with Other Regional and Global Ground-Motion Models

We examined the differences between the ground-motion estimations of local and global prediction equations and explored some seismological parameters that may explain these differences. To achieve this objective, we first derived a set of ground-motion prediction equations (GMPEs) for estimating peak horizontal accel- eration, velocity, and pseudospectral acceleration using the recently compiled Turkish ground-motion database. The new GMPEs are comparable with the recent global GMPEs in terms of model sophistication, and they are based on a well-studied national dataset. Using global GMPEs from the Next Generation Attenuation of Ground Motions project (Power et al., 2008) and the pan-European Akkar and Bommer (2010) model, we observed that the discrepancy between local and global GMPEs is more prominent at small magnitudes provided that the GMPEs possess similar mag- nitude limits. Our more detailed comparisons with the pan-European Akkar and Bom- mer (2010) predictive model, as well as with the estimations from a combined Italian and Turkish accelerometric dataset, indicate that depth can be of importance for delineating the differences between local and global GMPEs.

Post-Earthquake Restoration Planning for Los Angeles Electric Power

This paper describes the application of a new discrete-event-simulation model of the post-earthquake electric power restoration process in Los Angeles. The findings are that (1) Los Angeles residents may experience power outages lasting up to 10 days; (2) what we call the power rapidity risk (the joint probability distribution of restoration of a specified number of customers in a specified amount of time) varies throughout the area; (3) there is a relatively high likelihood that more repair materials than are currently available will be required if a large earthquake occurs; and (4) there are ways to reduce the expected duration of earthquake-initiated power outages and they should be subjected to cost-benefit analysis. These results should be useful to utilities and emergency planners in Los Angeles. The new simulation modeling approach could be used in other seismically active cities to gain insights into the restoration process that other modeling approaches cannot provide.

Discrete event simulation of the post-earthquake restoration process for electric power systems

This paper describes a discrete event simulation model of the post-earthquake restoration process for electric power systems. The model explicitly represents the real-life restoration process, enabling development of geographically disaggregated, quantitative restoration curves with uncertainty bounds, a dynamic map showing the spatial distribution of outages changing over time, and information on how personnel and repair materials are used throughout the process. The new restoration modelling approach is applied to the Los Angeles Department of Water and Power electric power system. Simulation results for the 1994 Northridge earthquake indicate that the model is capable of accurately estimating the restoration time and spatial sequence of the recovery process. The model aims to help improve the quantitative restoration time estimates that are required to estimate economic losses due to business interruption caused by power outages, and identify and compare the effectiveness of different ways to improve the restoration process in future earthquakes.

A Comparative Study of European Earthquake Loss Estimation Tools for a Scenario in Istanbul

A damage estimation exercise has been carried out using the building stock inventory and population database of the Istanbul Metropolitan Municipality and selected European earthquake loss estimation packages: KOERILOSS, SELENA, ESCENARIS, SIGE, and DBELA. The input ground-motions, common to all models, correspond to a “credible worst case scenario” involving the rupture of the four segments of the Main Marmara Fault closest to Istanbul in a Mw 7.5 earthquake. The aim of the exercise is to assess the applicability of the selected software packages to earthquake loss estimation in the context of rapid post-earthquake response in European urban centers. The results in terms of predicted building damage and social losses are critically compared amongst each other, as well as with the results of previous scenario-based earthquake loss assessments carried out for the study area. The key methodological aspects and data needs for European rapid post-earthquake loss estimation are thus identified.

Efficient simulation-based discrete optimization

In many practical applications of simulation it is desirable to optimize the levels of integer or binary variables that are inputs for the simulation model. In these cases, the objective function must often be estimated through an expensive simulation process, and the optimization problem is NP-hard, leading to a computationally difficult problem. We investigate efficient solution methods for this problem, and we propose an approach that reduces the number of runs of the simulation by using ridge regression to approximate some of the simulation calls. This approach is shown to significantly decrease the computational cost but at a cost of slightly worse solution values.

A Predictive Ground-Motion Model for Turkey and Its Comparison with Recent Local and Global GMPEs

We present a local ground motion prediction equation (GMPE ) for estimating the peak ground-motion values that was derived using the recently compiled Turkish strong motion database . The new GMPE is comparable with the recent global GMPEs in terms of model sophistication and quality of underlying database. Using this equation, we explore the inter-event , inter-station ground motion variability of the recent Turkish strong motion database as well as suitability of some local and global GMPEs for regional seismic hazard assessment analyses. The inter-event error underlines the distinguishing characteristics of few earthquakes, suggesting that the use of local GMPEs can be important especially when specific scenario studies are to be carried out. The inter-station variability allowed us to detect stations with outlier site response and to investigate the goodness of the employed site effect s model. Results also indicate suitability of some global and local GMPEs for use in regional seismic hazard assessments together with the model presented in this study. These should be combined through a logic tree scheme to reduce both aleatory and epistemic uncertainty in local hazard assessments.

Development of Earthquake Lossmap for Europe

For almost real-time estimation of the losses after a major earthquake in the Euro-Mediterranean region, the Joint Research Area-3 (JRA-3) component of the European Union (EU) Project “Network of Research Infrastructures for European Seismology – NERIES” foresees (at several levels of sophistication): 1. Finding the most likely location of the source of the earthquake using regional seismotectonic data base; 2. estimation of the spatial distribution of selected site-specific ground motion parameters; 3. correlation/verifyication/enrichment of the estimated ground shaking information with the available on-line strong motion data; and 4. estimation of physical damage and casualty distributions. These LossMaps will provide the required vital information within minutes after an earthquake to European emergency response agencies, in a manner similar to the United States Geological Survey (USGS)s Prompt Assessment of Global Earthquakes for Response (PAGER) system. A methodology that incorporates the regional dependencies and sources of uncertainty stemming from ground motion predictions, fault finiteness, site modifications, inventory of elements subjected to the hazard, and the vulnerability relationships is under preparation with researchers from Imperial College, NORSAR and ETH-Zurich. A pilot application is established for Turkey that encompasses the gridded earthquake source, Quaternary, Tertiary, Mesozoic (QTM) geological classification and physical and demographic inventory mapping for the whole country. Within the scope of this study, loss estimations were computed for the 1999 Kocaeli earthquake using several approaches and comparisons made with observed values. The LossMap tool will be available for the first estimation of damage immediately after an earthquake in Turkey by the end of 2007 and for the whole Euro-Med region by the end of 2009.

Erratum to: A model for predicting vertical component peak ground acceleration (PGA), peak ground velocity (PGV) and 5% damped pseudospectral acceleration (PSA) for Europe and the Middle East

In this study, we present a ground-motion model for the vertical component of peak ground acceleration, peak ground velocity, and 5% damped pseudo acceleration response spectra at periods ranging from 0.01 to 4 s. The vertical model is based on the ground-motion models previously developed for the horizontal component and vertical-to-horizontal ratio of ground motion by Akkar et al. (Bull Earthq Eng 12:359–387, 2014a; 517–547, 2014b) rather than on an independent regression analysis of strong-motion data available for Europe and the Middle East. The proposed ground-motion model includes formulations for the median values as well as for the aleatory within-event, between-event, and total standard deviation values of the vertical ground motion. We validate the proposed model by comparing it against the strong-motion database of Europe and the Middle East. Our vertical ground-motion model is applicable for moment magnitudes ranging from 4.0 to 8.0, for source-to-site distances ranging from 0 to 200 km, average shear-velocity down to 30 m (Vs30) values ranging from 150 to 1200 m/s and for reverse, normal and strike-slip styles of faulting as is the case for the underlying horizontal component and vertical-to-horizontal ratio ground-motion models of Akkar et al. (2014a, b). Within the scope of this study, a method to develop a vertical spectrum that is fully consistent with the corresponding horizontal uniform hazard spectrum is also proposed.