The city of Adapazarı -located in the Marmara Region of northwest Turkey -is situated on a deep sedimentary basin and was the city most heavily damaged by the strong ground motion of the 17 August 1999 Kocaeli earthquake (moment magnitude M w = 7.4). This study determines site amplifications of the attenuation relationships for shallow earthquakes in the Adapazarı basin by using the previous ground motion prediction equations (GMPEs) and the traditional spectral ratio method. The site amplifications are determined empirically by averaging the residuals between the observed and predicted peak ground acceleration (PGA) and spectral acceleration (SA) values for various periods. Residuals are significantly correlated with the known characteristics of geological units. A new attenuation model has also been developed for 5% damped spectral acceleration to determine the dependence of strong ground motions on frequency.Site amplification was evaluated at ten stations located in the Adapazarı basin. The PGA site amplification values varied between 1.130 and 3.120 in all stations except two; these exceptions resulted in de-amplifications. Calculated de-amplification values of these stations indicate a consistency for rock medium. The site amplification values of some stations indicate an increase while moving away from the surface rupture and approaching the contact between the alluvial deposits and bedrock. One station, located on the discontinuity between the two different media, has the highest site amplification value (3.12) in the study area. This high value might be a result of the focusing of the seismic waves due to the discontinuities located on both sides of the narrow basin.The traditional spectral ratio method was also used to determine amplification in the Adapazarı basin. One station on bedrock was chosen as a reference station. When the results of this method are evaluated, the amplifications at high periods are attributed to the thick sedimentary deposits in the basin and the apparent de-amplifications at low periods are partly due to the reference site response.When the spectral ratios or spectral residuals of the stations located on alluvial deposits or soft soils are considered, it is observed that these stations have high spectral ratio or residual values, especially at high periods. The source of these high period E. Ulutaş et al.

Recent mass movements in the Kocaeli Province, Turkey in 2010 caused damage to people, property and infrastructure, especially in Izmit and its vicinity. The causes and impact of these mass movements are outlined, so as to increase awareness of their dangerous aspects. Some of these mass movement events took place in urban areas, bringing attention to the need for better and more effective land use practices. The impact of these movements indicates the benefit there would be from geology and engineering geology in the planning of any property development and land use.Mass movement is the downward movement of materials such as soils, rock fragments and the combination of these on a slope due to the gravitational force. These movements are categorized based on the type of movements such as falls, slides and flows. A number of mass movements occurred in several places during the first two months of 2010 within the Kocaeli Province, which is located in north-west Turkey. A rock fall, two landslides and several earthflow types of mass movement were observed and caused injury and damage to property, and damaged and blocked the main roads. This damage was reported in both the local and national newspapers and was also covered on television channels. Although the details of these movements were broadcast, little was known of their geological and engineering geological perspective. Therefore, we set out to define and locate the mass movements, consider their geological background, and make some recommendations. Geographical Information System (GIS) was used to map the geology and the mass movement locations. Figure 1 displays the location of the study area, location of the mass movements and the geological formations and units in the region. Geology

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Abstract. On 23 October 2011, a Mw = 7.2 earthquake occurred in the Van Province in eastern Turkey, killing 604 people. The earthquake was triggered by a thrust fault due to a compression stress in the region, and caused extensive damage over a large area. Many structures in the earthquake region collapsed, and the damage spread from the city of Van to the town of Erciş, in a distance of 60 km. The earthquake generated several slope movements and liquefaction failures in the region, and this study evaluates these processes from the perspective of engineering geology, and presents field and laboratory results related to these processes. Attenuation relationships were used for estimation of peak ground accelerations (PGAs), and an empirical liquefaction evaluation method employing ground accelerations was used to define threshold accelerations initiating the liquefaction. The results demonstrate that landslides were widespread and more frequently observed in the field in comparison with earthflows and rockfalls. Flow-type liquefaction and lateral spreading was found to be widespread and more common than the liquefaction-related settlement. The minimum threshold acceleration value for the initiation of soil liquefaction was calculated to be 188.87 cm s−2 (~0.19 g) in the earthquake region. Laboratory results indicated that the soil liquefaction was closely associated with grain size. The slope instabilities, liquefaction and associated ground failures occurred mainly in rural areas, and their impact on structures was quite low as compared to the human loss and structural damage by the earthquake.

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