Brief communication "Fast-track earthquake risk assessment for selected urban areas in Turkey"

This study is presented as a contribution to earthquake disaster mitigation studies for selected cities in Turkey. The risk evaluations must be based on earthquake hazard analysis and city information. To estimate the ground motion level, data for earthquakes with a magnitude greater than 4.5 and an epicenter location within a 100-km radius of each city were used for the period from 1900 to 2006, as recorded at the Kandilli Observatory and Earthquake Research Institute. Probabilistic seismic hazard analysis for each city was carried out using Poisson probabilistic approaches. Ground motion level was estimated as the probability of a given degree of acceleration with a 10% exceedence rate during a 50-year time period for each city. The risk level of each city was evaluated using the number of houses, the per-capita income of city residents, population, and ground motion levels. The maximum risk level obtained for the cities was taken as a reference value for relative risk assessment, and other risk values were estimated relative to the maximum risk level. When the selected cities were classified according to their relative risk levels, the five most risky cities were found to be, in descending order of risk, Istanbul, Izmir, Ankara, Bursa, and Kocaeli

Notes on the history of geophysics in the Ottoman Empire

In Anatolia, the history of geophysical sciences may go back to antiquity (600 BC), namely the period when Thales lived in Magnesia (Asia Minor). In the modern sense, geophysics started with geomagnetic works in the 1600s. The period between 1600 and 1800 includes the measurement of magnetic declination, inclination and magnetic field strength. Before these years, there is a little information, such as how to use a compass, in the <i>Kitab-i Bahriye</i> (the Book of Navigation) of Piri Reis, who is one of the most important mariners of the Ottoman Empire. However, this may not mean that magnetic declination was generally understood. The first scientific book relating to geophysics is the book <i>Fuyuzat-i Miknatissiye</i> that was translated by Ibrahim Müteferrika and printed in 1731. The subject of this book is earth's magnetism. There is also information concerning geophysics in the book <i>Cihannuma</i> (Universal Geography) that was written by Katip Celebi and in the book <i>Marifetname</i> written by Ibrahim Hakki Erzurumlu, but these books are only partly geophysical books. In Istanbul the year 1868 is one of the most important for geophysical sciences because an observatory called Rasathane-i Amire was installed in the Pera region of this city. At this observatory the first systematic geophysical observations such as meteorological, seismological and even gravimetrical were made. There have been meteorological records in Anatolia since 1839. These are records of atmospheric temperature, pressure and humidity. In the Ottoman Empire, the science of geophysics is considered as one of the natural sciences along with astronomy, mineralogy, geology, etc., and these sciences are included as a part of physics and chemistry

Geotechnical and geophysical studies for wind energy systems in earthquake-prone areas: Bahce (Osmaniye, Turkey)case

Wind energy structures are systems related to the conversion of wind energy into useful form by wind power. They are subjected to strong dynamic and static loads. For this reason, an integrated site/soil investigation is required for all phases of project. In this context, there are several geotechnical/ geophysical criteria and requirements such as settlement criteria, stiffness requirements, ground water and dewatering requirements, excavation criteria, etc. Geotechnical and geophysical studies should include possible degradation of soil and rock due to cyclic loading over expected years of operation, bearing capacity, surcharge soil erosion due to drainage of storm water, differential settlements and consolidation settlements, etc. All soil layers that influence settlement and stiffness of foundation must be investigated. Study area is seismically active region and bounded in Bahçe district of Osmaniye City, in Turkey. The geodynamics of the region are controlled by the collision of the Arabian and Eurasian Plates. The East Anatolian Fault Zone, major seismogenetic source of project area is a 550 km-long, approximately northeast-trending, left lateral strike-slip fault. An (deterministic and probabilistic) earthquake hazard analysis was applied to region to estimate the ground motion level in engineering bedrock. Several geotechnical/geophysical tests and boreholes were performed in area to obtain better settlement, stiffness, bearing capacity, degradation properties. © 2009 Academic Journals

Technical guidelines for the assessment of earthquake induced liquefaction hazard at urban scale

Microzonation for earthquake-induced liquefaction hazard is the subdivision of a territory at a municipal or submunicipal scale in areas characterized by the same probability of liquefaction manifestation for the occurrence of an earthquake of specified intensity. The liquefaction hazard at a site depends on the severity of expected ground shaking as well as on the susceptibility to liquefaction of that site. This in turn depends on geological, geomorphological, hydrogeological and geotechnical predisposing factors. Thus, liquefaction hazard implies the existence of territories characterized by a moderate to high level of intensity of expected ground shaking. Microzonation charts for ground shaking and liquefaction hazard play a key role for the mitigation of seismic risk of an urban centre as they provide a valuable tool for the implementation of prevention strategies and land use planning. The LIQUEFACT project fully addressed the problem of microzoning a territory for earthquake-induced liquefaction hazard in a specific work package. Four municipal testing areas were selected across Europe as peculiar case studies where to construct microzonation charts for earthquake-induced liquefaction hazard. They are located in Emilia-Romagna region (Italy), Lisbon metropolitan area (Portugal), Brežice territory (Slovenia) and Marmara region (Turkey). Their location was identified based on the following criteria: severity of expected seismic hazard, availability of geological and geotechnical data, presence of liquefiable soil deposits, documented cases of liquefaction manifestations occurred in historical earthquakes, representativeness of different geological settings, density of population in selected areas (exposure). This paper illustrates the general procedure developed in LIQUEFACT for the assessment of earthquake-induced liquefaction hazard at urban scale and presents the main achievements of the microzonation studies carried out at the four previously mentioned European testbeds. Since the microzonation studies have been carried out using a shared framework and methodology, this paper has the ambition to serve as technical guidelines for updating the standards and the operational criteria currently used in different countries worldwide to construct seismic microzonation maps of liquefaction hazard