Ground Deformations Observed After 23.10.2011 M\u3csub\u3ew\u3c/sub\u3e 7.2 VAN Earthquake (Turkey)

A destructive earthquake with a moment magnitude of 7.2 occurred in the north of the Van province (Turkey) on 23rd October 2011 at 13:41 local time and caused approximately 600 deaths and more than 4000 injuries. Many damaging aftershocks were recorded for more than a month after the main shock including a triggered earthquake (Mw 5.6) located in the southern district of Van, namely Edremit, on November 9th, 2011 which caused additional damage and casualties. After the Mw 7.2 Van earthquake, earthquake-induced ground deformations such as liquefaction and lateral spreading were extensively observed around the shores of Lake Van and in the floodplains of rivers. The Karasu River floodplain, which is one of the major streams in the region, severely suffered from liquefaction and lateral spreading. In this study, a brief overview of the Mw 7.2 Van earthquake as well as earthquake-induced ground deformations is presented. Then, the results of field reconnaissance on liquefaction and lateral spreading features observed in the Karasu River floodplain are explained. Furthermore, subsurface characteristics of liquefied layers are documented considering the data obtained from a borehole drilled just on top of the sand boil after the earthquake. The borehole data indicate that the liquefaction occurred in a sandy zone with very shallow groundwater level in the Karasu River floodplain

Investigation of the Macro Pore Geometry of Yellow Travertines Using the Shape Parameter Approach

Porosity is one of the most important physical properties of rocks. Strength and deformation parameters as well as the effect and degree of weathering are also related to porosity. Rocks with high porosity are more vulnerable to weathering than are non-porous rocks. Consequently, identification of pore size and shape may assist the evaluation of strength characteristics and resistance to weathering. One approach used for the determination of macro pore geometry is the stereology method. The main principle of the stereology method is based on the analysis of three-dimensional solid materials on a two-dimensional surface. The macro pore geometry of rocks can be evaluated by the shape parameter ( F) concept, which depends upon the stereology method. Shape parameter is an explanation of pore geometry on a rock surface using the perimeter and area of the pores. Here, the shape parameter approach is utilized for the determination of the macro pore geometry in travertines. Studies were performed on yellow travertine cut slabs at the memorial mausoleum (Anitkabir) of the great Turkish leader Ataturk in Ankara, Turkey, and on fresh surfaces of the same rock in the quarries from which the slabs originated. Pore perimeter and pore area were calculated using Geographical Information System software. These shape parameters of the macro pores on travertine pillars and on fresh travertine cuts were then compared. As a result, a slight pore geometry difference between air-exposed and fresh yellow travertine was determined based on the statistical evaluations

Evaluation of liquefaction in Karasu River floodplain after the October 23, 2011, Van (Turkey) earthquake

The eastern shore of Lake Van was shaken by a powerful earthquake (M (w) 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the Van Province, which is one of the main cities in the Eastern Anatolia. The Van Province and particularly its largest district Ercis were adversely affected by the earthquake, and unfortunately, a total of 600 people lost their lives. Besides severe constructional damages and building collapses, ground deformations were widespread at many locations nearby the Lake Van and Karasu River floodplain. Numerous sand boils and lateral spreading cracks were observed at the left and right embankments of the Karasu River, which is one of the major streams in the region. In this study, field observations on liquefaction and lateral spreading features triggered by the M (w) 7.2 Van earthquake are initially presented. Then, the results of subsurface investigations including trial pits, drillings and geophysical surveys on specific large-scale sand boils are explained. Subsequently, liquefaction back-analysis is performed considering the gathered subsurface data. The analysis indicates that the liquefaction occurred in a shallow zone with approximately 4 m thickness in the investigated area. The Liquefaction Potential Index method reveals high liquefaction potential for the analyzed sand boil location. In addition, the effect of cap soil thickness on liquefaction is once more validated by this case

Evaluation of the physico-mechanical parameters affecting the deterioration rate of Ahlat ignimbrites (Bitlis, Turkey)

The paper principally focuses on the durability assessment of various stratigraphic levels of Ahlat ignimbrites collected from the eastern region of Turkey. A total of four different ignimbrite types with dissimilar color, texture and particularly welding degree were tested in laboratory. The laboratory tests performed on the ignimbrite specimens indicate that the welding degree as well as the lithic material content mainly controls the strength and capillarity properties of the ignimbrites. In addition, the durability of highly porous ignimbrites strongly depends upon the degree of welding. The effect of several weathering agents on the ignimbrites was evaluated on the basis of decay constant parameter. Accordingly, salt and ice crystallization pressures are a couple of major destructive agents acting within the micropores of the ignimbrites. Conversely, the investigated specimens are relatively durable against cyclic wetting-drying. Statistical evaluations reveal that the pore diameter is the major controlling factor on the deterioration rate of the ignimbrites after specifically recurrent freeze-thaw cycles. Moreover, the dry unit weight of the ignimbrites is more significant than the uniaxial compressive strength considering the deterioration rates during wetting-drying and salt crystallization. A less significant relationship was obtained between pore diameter and salt crystallization decay constant

Assessment of the effectiveness of a rockfall ditch through 3-D probabilistic rockfall simulations and automated image processing

Rockfall ditches or catchment areas aim to collect falling blocks at the toe of a source zone by dissipating the energy of blocks in an excavated trench. The effectiveness of a rockfall ditch is simply expressed by its block catchment performance and can be evaluated by empirically using existing design charts as well as rockfall simulations. Although 2-dimensional (2-D) analysis has been executed to assess the catchment ditch effectiveness in engineering practice, 3-dimensional (3-D) rockfall models have not received enough attention so far. In this study, the effectiveness of a considerably long rockfall ditch to protect a settlement from falling rocks was assessed on the basis of 3-D rockfall analyses executed using high-resolution digital surface models. The rockfall ditch efficiency was found to be moderate to limited for various segments considering the percentage of blocks not trapped by the ditch. Moreover, the sensitivity of ditch efficiency to ditch depth was analyzed by automated image processing method as well. Additionally, a particular section of ditch alignment was fictitiously excavated or filled by synthetic Digital Surface Model (DSM) generation through image processing. 3-D rockfall modeling carried out using the DSMs with synthetically manipulated ditches points out that the effectiveness of a catchment ditch is highly depended upon ditch depth. Even a small volume of block accumulation inside the ditch definitely reduces the ditch performance resulting extended runout distances reaching to residential area. Finally, 3-D rockfall modeling is accepted to be an effective tool to rate the efficiency of existing rockfall ditches and synthetically generated ditches on DSMs (or DEMs) by means of automated image processing method may assist the control of current ditch dimension as well as new catchment ditch design

Evaluation of the Relationship between Welding Degree and the Shape of Lithic Fragment for İgnimbrites

Piroklastik bir kaya türü olan ignimbirit, oluşumu esnasındaki sıcaklık (>535˚C) ve basınç koşullarına bağlı olarak farklı kaynaşma derecelerine sahip olabilir. İgnimbiritlerde kaynaşmayı kontrol eden en önemli faktörler olan oluşum sıcaklığı ve depolanma ortamındaki örtü yükü kalınlığı arttıkça ignimbiritlerdeki kaynaşma derecesi artmaktadır. Artan oluşum sıcaklığı ile ignimbiritlerde plastik deformasyon gözlenir ve içerdikleri camsı minerallerde kaynaşma meydana gelir. Bununla birlikte, depolanmayla birlikte artan örtü yükü kalınlığı, alt bölümlerde yer alan ignimbiritlerdeki kül hamurunun ve içerisinde bulunan pomza tanelerinin deforme olmasına neden olur. Bu deformasyon sırasında litik malzemeler farklı oranlarda yassılaşmış bir şekil alırlar. Yüksek deformasyonla birlikte ignimbiritlerin pomza taneleri merceksi bir yapı kazanmakta ve kaya daha kaynaşmış hale gelmektedir. İgnimbiritlerin kaynaşma derecesinin artması, kayanın fiziko-mekanik özelliklerinde de iyileşmesine neden olmaktadır. Bu araştırma kapsamında ülkemizde ignimbiritlerin yaygın olarak gözlendiği üç ayrı bölgeden (Kayseri, Nevşehir, Ahlat) elde edilen farklı renk ve doku özellikleri sunan 16 farklı ignimbirit türü üzerinde petrografik, mineralojik, jeokimyasal çalışmalar gerçekleştirilmiş ve bu örneklerin fiziksel ve mekanik özellikleri ortaya konmuştur. Bunun yanı sıra, aynı ignimbirit örneklerinde bulunan pomza ve diğer kayaç parçalarından oluşan litik tanelerin uzun ve kısa eksen uzunlukları mikroskop altında ölçülerek belirlenmiş ve farklı şekil parametresi değerlendirme yöntemleri ile şekil oranları ortaya konmuştur. Genel olarak değerlendirildiğinde Kayseri ve Ahlat ignimbiritlerinde pomza tanelerinin daha merceksi bir yapıda olduğu ortaya konmuştur. Nevşehir ignimbiritlerinde pomza taneleri merceksi bir yapı kazanmamışlardır. Öte yandan, tüm ignimbirit örneklerinde diğer kayaç parçalarına ait litik tanelerde belirgin bir yassılaşma olmadığı ortaya konmuştur. Dayanım açısından incelendiğinde Kayseri ignimbiritleri çoğunlukla diğer ignimbirit türlerine göre daha yüksek dayanımlıdır. En düşük dayanıma Nevşehir ignimbiritleri sahiptir. Araştırmanın amaçlarından biri olarak, ignimbiritlerdeki farklı fiziksel ve mekanik özellikler ile pomza tanelerindeki yassılaşma oranları arasındaki istatistiksel ilişkiler araştırılmıştır. Basit regresyon analizleri sonucunda en anlamlı ilişkinin pomza tanelerinin en-boy ve basıklık oranı şekil parametreleri ile ignimbiritlerin tek eksenli basınç dayanımı arasında olduğu belirlenmiştir. Bu ilişkiye göre, pomzalardaki basıklık oranı (yassılık) arttıkça malzeme dayanımı da yükselmektedir. Öte yandan, bu araştırma projesi sonucunda ignimbiritlerin kaynaşma derecesinin değerlendirilebilmesi için bölgede yapılmış diğer araştırma sonuçları da veri tabanına dahil edilerek ignimbiritler için tek eksenli basınç dayanımı ve kuru birim hacim ağırlık kullanılarak bir kaynaşma derecesi sınıflaması geliştirilmiştir. Önerilen kaynaşma sınıflaması kaynaşmamış ile çok iyi derecede kaynaşmış arasında değişen altı sınıftan oluşmaktadır. İncelenen ignimbiritlerin kaynaşma dereceleri değerlendirildiğinde Kayseri ignimbiritleri çoğunlukla orta derecede kaynaşma özelliği sergilemektedir. Nevşehir ignimbiritleri ise az kaynaşmış bir yapıya sahiptir. Ahlat ignimbiritlerinde ise kaynaşma derecesi az dereceden iyi dereceye kadar değişebilmektedir. Aynı zamanda, ignimbiritlerin kaynaşma derecesi sınıfları ile pomza tanelerinin basıklık oranı (OR) değerlerinin farklı kaynaşma derecesindeki sınır değerleri kullanılarak yapılan sınıflama arasında büyük oranda benzerlik bulunmuştur