What is to be learned from damage and failure of reinforced concrete structures during recent earthquakes in Turkey

The effect of pH of water and mineralogical properties on the slake durability (degradability) of different rocks from the Lesser Himalaya, India

Geometry of co-seismic surface ruptures and tectonic meaning of the 23 October 2011 Mw 7.1 Van earthquake (East Anatolian Region, Turkey)

Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4Ma

The historically active Nemrut Volcano (2,948 m asl) (Eastern Anatolia), rising close to the western shore of huge alkaline Lake Van, has been the source of intense Plinian eruptions for >530,000 years (drilled lake sediments). About 40 widespread, newly recognized trachytic and less common rhyolitic fallout tephras and ca. 12 interbedded ignimbrites, sourced in Nemrut Volcano, are documented in stratigraphic traverses throughout an area of >6,000 km2 mostly west of Lake Van. Phenocrysts in the moderately peralkaline trachytes and rarer large-volume comenditic rhyolites comprise anorthoclase, hedenbergite-augite, fayalite and, especially in trachytic units, augite, minor aenigmatite, apatite and quartz, and rare chevkinite and zircon. Dacitic to rhyolitic tephras from nearby calcalkalic Suphan Volcano (4,058 m asl), locally interbedded with Nemrut tephras, are characterized by disequilibrium phenocryst assemblages (biotite, augitic clinopyroxene and hypersthene, minor olivine, common crystal clots and/or, in some deposits, amphibole). The magma volume (DRE) of the largest Nemrut tephra sheet (AP-1) described in detail may exceed 30 km3. Extreme facies and systematic compositional changes are documented in the ca. 30 ka Nemrut Formation (NF) deposits formed from one large and complex eruption (thick rhyolitic fallout overlain by ignimbrite, welded agglutinate, overbank surge deposits, and final more mafic fallout deposits). Common evidence of magma mixing in Nemrut ignimbrites reflects eruption from compositionally zoned magma reservoirs. Several young Cekmece Formation trachytes overlying ca. 30 ka old NF deposits and the late trachytes of the NF deposits show compositional affinities to tephra from Suphan Volcano possibly due to temporary influx of Suphan magmas into the Nemrut system following the evacuation of >10 km3 magma (DRE) during the caldera-forming NF eruption. Axes of large fallout fans are dominantly SW–NE but W–E in the younger sheets resembling the direction of the present dominant wind field. Growth of Nemrut volcanic edifice and its peripheral domes since before 0.5 Ma in the hinge area between the Van and Mus tectonic basins is likely to have been the major factor in isolating Lake Van basin thus initiating the origin and subsequent alkaline evolution of the lake. This alkalinity was later significantly controlled by climate forcing. Internal forcing mechanisms (volcanic and geodynamic) may also have contributed to major lake level changes in addition to climate forcing.

Impact of volcanism on the evolution of Lake Van I: evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past >400,000 years

The seismic hazard for the Lake Van basin is computed using a probabilistic approach, along with the earthquake data from 1907 to present. The spatial distribution of seismic events between the longitudes of 41–45° and the latitudes of 37.5–40°, which encompasses the region, indicates distinct seismic zones. The positions of these zones are well aligned with the known tectonic features such as the Tutak-Caldiran fault zone, the Ozalp fault zone, the Gevas fault zone, the Bitlis fault zone and Karliova junction where the North Anatolian fault zone and East Anatolian fault zone meet. These faults are known to have generated major earthquakes which strongly affected cities and towns such as Van, Mus, Bitlis, Ozalp, Muradiye, Caldiran, Ercis, Adilcevaz, Ahlat, Tatvan, Gevas and Gurpinar. The recurrence intervals of M
 s ≥ 4 earthquakes were evaluated in order to obtain the parameters of the Gutenberg–Richter measurements for seismic zones. More importantly, iso-acceleration maps of the basin were produced with a grid interval of 0.05 degrees. These maps are developed for 100- and 475- year return periods, utilizing the domestic attenuation relationships. A computer program called Sistehan II was utilized to generate these maps.

Probabilistic seismic hazard assessment for Lake Van basin, Turkey

It is known that foundation problems are caused by the dissolution of gypsum due to both chemical and mechanical processes. In order to investigate the combined effect of physico-chemical agents on the erodability of gypsum, a series of slake durability tests were carried out on eight different types of gypsum using testing solutions with different pH values. XRD, chemical and petrographical analyses, and basic strength tests such as unconfined compression, Brazilian tensile, and point load were performed on the eight rock types. The slake durability results ranged from medium to very high under the different pH conditions but it was concluded that the slake durability of gypsum is independent of the pH of the testing solution. Mineralogical composition and fabric are considered to have a greater influence on the slake durability of gypsum.

The effect of the pH of the testing liquid on the slake durability of gypsum

Liquefaction-related building damage in Adapazari during the Turkey earthquake of August 17, 1999

For Anatolian earthquakes, there are insufficient strong motion data from rock sites to model an attenuation relationship for Turkey. This necessitates the use of records from soil sites, which are significantly affected by amplification. In order to include soil site data in the attenuation analyses, boreholes were drilled at 64 recording stations on soil sites. After removing the effects of soil amplification, rock site and soil site data were combined to establish an attenuation relationship. Various models were tested through regression analyses using moment magnitude, epicentral distance and threshold peak horizontal ground acceleration. A new attenuation relationship is modeled for Turkey.

Strong motion attenuation relationship for Turkey—a different perspective

Changes to physical and mechanical properties of pyroclastic flow deposits occur during welding process, resulting from overburden pressure and temperature. A great deal of research has been carried out to identify which physical parameters can enable quantification of the degree of welding within pyroclastic deposits. Material properties, such as density, porosity, hardness, abrasion, and compressive and flexural strength, are critical in assessing the suitability of natural stone as a building material, but they have not been sufficiently integrated. Therefore, an attempt has been made to develop a welding classification which integrates measurements of material properties with petrographic and textural observations. The proposed classification covers physical, index, and strength parameters for pyroclastic flow deposits. The most important aspect of this investigation has been the quantification of material parameters and definition of a welding classification applicable to a wide range of ignimbrites, from nonwelded to densely welded, that are used as natural building stone. This welding classification is proposed to ensure a consistent approach in characterizing key aspects of welded facies in pyroclastic deposits and in the identification of natural stone reserves.

Turgay Beyaz

Papers

Probabilistic seismic hazard assessment for Lake Van basin, Turkey

The effect of the pH of the testing liquid on the slake durability of gypsum

Liquefaction-related building damage in Adapazari during the Turkey earthquake of August 17, 1999

Strong motion attenuation relationship for Turkey—a different perspective

Welding intensity assessment of pyroclastic units based on engineering quality requirements