Mustafa Erdik

Site-Specific Issues for Strong Ground Motions during the Kocaeli, Turkey, Earthquake of 17 August 1999, as Inferred from Array Observations of Microtremors and Aftershocks

Array observations of microtremors and aftershocks were carried out near the permanent strong-motion observation sites and the damaged areas, after the Kocaeli, Turkey, earthquake of 17 August 1999. The major objectives were to determine S -wave velocity structures at the sites and to understand the site effects on strong motion or damage. Array observation of microtremors is a useful method for determining the S -wave velocity structures in a sedimentary basin, with less practical restriction than the other geotechnical methods. The spatial autocorrelation method (SPAC) was applied to array data of microtremors for determining S -wave velocity structures. The SPAC method generally provides an equivalent result with that of the frequency-wavenumber method, using fewer array sites and a smaller array size. Most strong-motion sites near the fault are classified into stiff and/or very hard soils. The records cannot directly be used for interpreting damage to buildings in the sedimentary basin. Records of long durations of strong motion at ATS, near Avcilar, west of Istanbul, are closely related to the low velocity ( V s ∼ 200 m/sec) of the surface layers. The S -wave velocity structure at Avcilar, where there was severe damage during the mainshock, is similar to that of the lowland (ATS), and it differs significantly from that of CNA, located 4 km northeast of Avcilar, where the strong-motion record was obtained from the mainshock. The strong ground motion at Avcilar during the mainshock is estimated to be similar to that at ATS. Of the strong-motion sites, Sakarya (SKR) is located on very hard soil, whereas thick and soft sediments cover downtown Adapazari. It is plausible that strong ground motions during the mainshock in the damaged area, ADC, were significantly different from those of SKR. A large difference between the strong motions of a hillside and the lzmit Bay area in and around Golcuk is also indicated by a comparison of aftershock records.

Development of an earthquake loss model for Turkish catastrophe insurance

Following the devastating Kocaeli and Düzce earthquakes of August andNovember 1999, the Turkish Government was faced with an enormousfinancial burden as a result of its statutory obligation to cover the full costsof rebuilding. In order to offset this liability in the future – which has hadan adverse effect on the Governments economic programme – acompulsory earthquake insurance scheme has been introduced for allhouseholders in Turkey. A key element for successful implementation ofthis novel and ambitious programme is the transfer of the earthquake riskabsorbed by the Turkish Catastrophe Insurance Pool (TCIP) to theinternational reinsurance market. An earthquake loss model, described inthis paper, has been developed for the TCIP to serve as a basis for thedecision-making process with respect to the pricing of its insurance policy,risk control, the purchase of reinsurance, and the transfer of seismic risk.Sample results of the loss calculations are presented.

Rapid Earthquake Loss Assessment After Damaging Earthquakes

This article summarizes the work done over last decades regarding the development of new approaches and setting up of new applications for earthquake rapid response systems that function to estimate earthquake losses in quasi real time after an earthquake. After a critical discussion of relevant earthquake loss estimation methodologies, the essential features and the characteristics of the available loss estimation software are summarized. Currently operating near real time loss estimation tools can be classified under two main categories depending on the size of area they cover: Global and Local Systems. For the global or regional near real time loss estimation systems: GDACS, WAPMERR, PAGER, ELER and SELENA methodologies are. Examples are provided for the local rapid earthquake loss estimation systems including: Taiwan Earthquake Rapid Reporting System, Real-time Earthquake Assessment Disaster System in Yokohama, Real Time Earthquake Disaster Mitigation System of the Tokyo Gas Co., IGDAS Earthquake Protection System and Istanbul Earthquake Rapid Response System.

Selection of Ground Motion Prediction Equations for the Global Earthquake Model

Ground motion prediction equations (GMPEs) relate ground motion intensity measures to variables describing earthquake source, path, and site effects. From many available GMPEs, we select those models recommended for use in seismic hazard assessments in the Global Earthquake Model. We present a GMPE selection procedure that evaluates multidimensional ground motion trends (e.g., with respect to magnitude, distance, and structural period), examines functional forms, and evaluates published quantitative tests of GMPE performance against independent data. Our recommendations include: four models, based principally on simulations, for stable continental regions; three empirical models for interface and in-slab subduction zone events; and three empirical models for active shallow crustal regions. To approximately incorporate epistemic uncertainties, the selection process accounts for alternate representations of key GMPE attributes, such as the rate of distance attenuation, which are defensible from available data. Recommended models for each domain will change over time as additional GMPEs are developed.

Seismic Hazard in Istanbul following the 17 August 1999 İzmit and 12 November 1999 Düzce Earthquakes

Two recent destructive earthquakes that occurred along the western part of the North Anatolian Fault Zone (NAFZ), the 17 August 1999 ( M w 7.4) Izmit and 12 November 1999 Duzce ( M w 7.2) earthquakes, have caused major concern about future earthquake occurrences and their possible consequences in the Istanbul area. Probabilistic seismic hazard analyses are performed for the larger Istanbul area including the Gulf of Izmit and the Marmara Sea region. Hazard computations were done assuming different combinations of four attenuation relations and three alternative source models. The three models used are (1) Standard Poissonian earthquake occurrence with area sources, (2) renewal model (assuming characteristic earthquakes) with area and fault sources, and (3) renewal model (assuming characteristic earthquakes) with refined area and fault sources. Results are presented in twelve different maps of peak ground acceleration (PGA) with a 10% chance of exceedance in 50 yr. Among the earthquake recurrence models, the results assuming model 3, yield the highest PGA values, reaching greater than 0.3 g at the western end of the Gulf of Izmit. In general, PGA values decrease toward north and are reduced down to less than 0.2 g in central Istanbul in the Bosphorous area. The four attenuation relations examined display significant variations, and their effects become especially critical for distances less than 50 km. In addition, spectral hazard levels (corresponding to 475-yr return period) are computed and presented as uniform hazard response spectra for 5% damping. Two sites are selected, one in hard rock and the other in soft sediments. In general, these results correlate well with the Turkish Seismic Design code (TSDC) recommendations for the two site conditions. The estimates of the future earthquake hazard potential of the Istanbul area are sensitive to our present-day understanding of the behavior of the fault segments in the Marmara Sea region.

23 October 2011 Van (Turkey) earthquake

An earthquake of Mw7.2 on 23 October 2011 occurred in the Van region of Eastern Turkey. The main shock and long series aftershocks caused significant damage and claimed 644 lives. The particular features and the lessons learned are covered.

Strong Ground Motion

The availability of empirical strong ground motion data will always be less that what would be needed to meet the needs of a variety of ever demanding engineering problems. A set of strong ground motions, either recorded or theoretically simulated, is the necessary database for the civil engineering design, regarding both new construction and performance assessment of the existing built environment. The future of performance based earthquake resistant design and sophisticated non-linear dynamic analysis will rely on the development of analytical tools that can simulate realistic ground motions in terms of tectonic structure, earthquake physics, local geological and geotechnical conditions. This need is more acute for large magnitude earthquakes in near-field conditions. The state-of-the art and success in strong ground motion simulation is developing at a fast rate and we all hope that it meets the demand in foreseeable future.

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.

Field evidence and numerical investigation of the \(\text{ M}_\mathrm{w}= 7.1\) October 23 Van, Tabanlı and the \(\text{ M}_\mathrm{W}> 5.7\) November earthquakes of 2011

On Sunday, October 23rd, 2011, the Van province, in the Eastern Turkey, was stricken by a magnitude \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}