A quantitative weathering classification system for yellow travertines

Weathering can cause adverse effects on the physico-mechanical properties of rocks. Although the processes and outcomes of weathering have been investigated for many rock types, the travertine weathering was not paid enough attention as much as the others. However, the unfavorable effects of weathering may arise rapidly due to travertine’s calcium carbonate composition and highly porous texture. Travertine is an important rock type in building stone market and is generally preferred as an exterior façade material. This rock type was also used in many historical buildings and sculptures in the past, and the signs of extensive weathering can be recognized on some of these travertine-made structures. In this study, it was aimed to characterize the effect of weathering on travertine’s structural properties. The yellow travertine from Eskipazar (Karabuk, Turkey) was selected as the study material and the samples with different weathering degrees were collected from site. The chemical, physical and mechanical properties of those samples were determined in laboratory. The physico-mechanical variations with progressive weathering grades were statistically evaluated and a weathering classification based on a rating system was proposed for yellow travertine in rock material scale. The newly developed system may assist in characterizing the degree of weathering for historical structures built by yellow travertine. Additionally, the classification may also guide to further researches on the weathering of different types of travertine.     

Time-dependent analysis of aftershock events and structural impacts on intraplate crustal seismicity of the Van earthquake (Mw 7.1, 23 October 2011), E-Anatolia

The Van earthquake (M _W 7.1, 23 October 2011) in E-Anatolia is typical representative of intraplate earthquakes. Its thrust focal character and aftershock seismicity pattern indicate the most prominent type of compound earthquakes due to its multifractal dynamic complexity and uneven compressional nature, ever seen all over Turkey. Seismicity pattern of aftershocks appears to be invariably complex in its overall characteristics of aligned clustering events. The population and distribution of the aftershock events clearly exhibit spatial variability, clustering-declustering and intermittency, consistent with multifractal scaling. The sequential growth of events during time scale shows multifractal behavior of seismicity in the focal zone. The results indicate that the extensive heterogeneity and time-dependent strength are considered to generate distinct aftershock events. These factors have structural impacts on intraplate seismicity, suggesting multifractal and unstable nature of the Van event. Multifractal seismicity is controlled by complex evolution of crustal-scale faulting, mechanical heterogeneity and seismic deformation anisotropy. Overall seismicity pattern of aftershocks provides the mechanism for strain softening process to explain the principal thrusting event in the Van earthquake. Strain localization with fault weakening controls the seismic characterization of Van earthquake and contributes to explain the anomalous occurrence of aftershocks and intraplate nature of the Van earthquake.     

钙华物理力学性质试验研究

钙华是一种大孔隙次生碳酸钙,是岩溶水在适宜的环境下碳酸钙过饱和沉积而形成,不同成因的钙华形成了绚丽多彩的自然景观。钙华沉积速率快,对气候和环境极具敏感性,近年来被广泛用于短时间尺度的古气候环境重建研究。由于钙华主要分布于水流活动频繁的偏远地区,较少用于工程建设,故国内外对其工程性质少有研究。本文以南美洲玻利维亚东南地区某冶金项目为依托,实地研究了湖沼相钙华的工程性质,通过渗水试验测试了钙华层的渗透系数,通过浸水载荷试验,研究了钙华的承载力特性和溶陷性。结果表明:钙华的渗透系数为1.7×10-3cm·s-1;变形模量为45.39 MPa,在浸水之后变形模量有所降低,但仍然可达到36.85 MPa;浸水状态下地基承载力特征值高于280 kPa,浸水3 h后的浸润深度为0.65 m;钙华的平均溶陷系数为0.001 75,为非溶陷性岩石。通过试验可以得出如下结论:(1)钙华遇水后的稳定性较差,基坑和基础施工宜安排在旱季。(2)钙华在天然状态下的承载力较高,遇水后承载力会有所降低,应尽可能保持基底干燥。③钙华的渗透系数较小,短时间的水流对钙华层的浸润深度较小,雨季来临时,只要做好地基的覆盖,就可以使地基保持较高的承载力。     

Kinematic analysis and palaeoseismology of the Edremit Fault Zone: evidence for past earthquakes in the southern branch of the North Anatolian Fault Zone,Biga Peninsula,NW Turkey

The Edremit Fault Zone (EFZ) forms one of the southern segments of the North Anatolian Fault Zone (NAFZ) at the northern margin of the Edremit Gulf (Biga Peninsula, South Marmara Region, Turkey). Stratigraphic, structural and kinematic results indicate that basinward younging of the fault zone, in terms of a rolling-hinge mechanism, has resulted in at least three discrete Miocene to Holocene deformational phases: the oldest one (Phase 1) directly related to the inactive Kazda? Detachment Fault, which was formed under N–S trending pure extension; Phase 2 is characterised by a strike-slip stress condition, probably related to the progression of the NAFZ towards the Edremit area in the Plio–Quaternary; and Phase 3 is represented by the high-angle normal faulting, which is directly interrelated with the last movement of the EFZ. Our palaeoseismic studies on the EFZ revealed the occurrence of three past surface rupture events; the first one occurred before 13178 BC, a penultimate event that may correspond to either the 160 AD or 253 AD historical earthquakes, and the youngest one can be associated with the 6 October 1944 earthquake (M_w = 6.8). These palaeoseismic data indicate that there is no systematic earthquake recurrence period on the EFZ.     

Environmental issues concerning natural resources at Pamukkale protected site,southwest Turkey

. Pamukkale protected site is located 20 km away from the provincial center of Denizli in southwest Turkey. This site has unique natural and cultural assets such as hot water springs, white travertine terraces, and cultural ruins of the ancient city of Hierapolis. The rising interest in this site leads to irreversible deterioration of natural and cultural assets. This study reveals the environmental issues, such as swimming activities, the lack of sewage treatment, mechanical damage, etc. on hot water springs and white travertine terraces. Swimming activities in the pools and sewage leakage from non-isolated cesspools encourage excessive microbial growth at the travertine surface resulting in the discoloration of white travertine terraces. Walking over the delicate travertine surface leads to the deformation of existing calcite crystals and delays the formation of the new crystals. Vehicle entry to the site causes damage, for example creating vibration, high gas emission, and dust airlifting. To ensure optimal protection conditions at this site, priority must be given to the maintenance, restoration, monitoring, and maximization of the natural resources, and special regulations and laws should be enacted. Although it must be realized that good resource management will never be able to completely solve the problems in conservation of this site, it is equally clear that a correct use of natural resources can help avoid worsening of an already difficult situation.     

Performance evaluation of the M8 algorithm to predict M7+ earthquakes in Turkey

The M8 algorithm is one of the most reliable intermediate-term middle-range earthquake prediction algorithms. The present study evaluates the ability of the M8 algorithm and its modified versions for predicting major events (M7+) in Turkey. Thirty different algorithms were developed by changing the radius of circle of investigation (CI) and the lower magnitude cutoff of the M8 algorithm. These modified algorithms were executed all over the territory of Turkey, and the results were evaluated using the error diagram. Each modified algorithm was executed for consecutive half-year intervals over a specified period of time. Subsequently, the seismic catalog was updated, and failures-to-predict ratio and the fraction of alarm were considered. Results showed that the location of areas of alarm change gradually over consecutive intervals, and no sudden changes can be observed. In addition, the annual changes of areas of alarm are not random and follow a pattern. This study also showed that the modified algorithm having a three to six annual average of events and a 393-km CI radius is an efficient algorithm for predicting the future seismic events in Turkey. This algorithm predicted six out of six target events, retrospectively, with a confidence level of 96.4 %. According to the obtained results, it will be possible to rely on this modified algorithm to predict near future earthquakes of Turkey. Furthermore, this study proves that it is possible to alter the M8 algorithm for being used in regional studies.     

Travitonics: using travertines in active fault studies

Late Quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures. On the basis of field studies in the Aegean region (Turkey and Greece), the northern Apennines (Italy) and the Basin and Range province (USA) we conclude that the following relationships are of predictive value: (i) travertine deposits are preferentially located along fracture traces, either immediately above extensional fissures or in the hanging walls of normal faults; (ii) the locations of many travertine fissure-ridge deposits coincide with step-over zones (relay ramps) between fault segments; networks of intersecting tensional fissures reflecting the complex strains experienced in such settings are probably responsible for enhancing hydrothermal flow; (iii) the morphology of travertine deposits overlying extensional fissures is controlled by the rheology of the underlying materials; tufa cones (towers, pinnacles) form on former and present lake floors where fissures underlie unconsolidated sediments, whereas fissure-ridges develop where fissures cut bedrocks at the surface; (iv) fissure-ridges comprise outwardly dipping bedded travertine flanking a central tensional fissure filled by vertically banded travertines; fissures can be used to infer local stretching directions; (v) where there are travertines datable by the U-series method it is possible to calculate time-averaged dilation and lateral propagation rates for individual fissures; (vi) most fissures cutting fissure-ridges comprise self-similar angular segments with fractal dimensions in the range 1.00–1.12, the properties of bedded travertine combined with stress perturbations at fissure tips probably being responsible for such similar fractal dimensions being inferred from such a wide range of locations. Fissures gradually increasing in width with depth are products of continuous fracture dilation in contrast to those that form during episodic dilation which display stepped increases of width with depth; (vii) travertine deposited from springs along fault zones accumulate in terraced-mounds sited down slope of the spring line; (viii) many post-depositional fractures cutting travertine deposits are locally oriented at right angles to deposit margins; and (ix) systematic joints in travertines are restricted to those parts of eroded sheet deposits that have been exhumed.     

October 23, 2011 Turkey/Van–Ercis earthquake: structural damages in the residential buildings

On October 23, 2011, a magnitude of Mw 7.2 earthquake struck the Van province in eastern Turkey which caused approximately 600 life loss and 4,000 injured people. Although the recorded peak ground accelerations were relatively low (0.15–0.2 g) compared with that of other recent destructive Turkish earthquakes and the code-based design response spectrum, a large number of reinforced concrete buildings with 4–6 stories and non-engineered masonry buildings were either heavily damaged or collapsed in the region. Based on the post-earthquake technical inspections, the goal of this paper is to introduce major reasons for structural damages in the disaster area and to discuss these failures along with the approaches given in the design code which is renewed after August 17, 1999 Marmara Earthquake. Some remarkable lessons learned from earthquake-induced failures and damages specific to building construction techniques are presented in this paper.     

The earthquakes and related tsunamis of October 6, 1944 and March 7, 1867; NE Aegean Sea

During two distinct earthquakes occurred on March 7, 1867 and October 6, 1944, tsunami waves were also observed at some localities around the Gulf of Edremit, NE Aegean Sea. The first event (M _w = 6.8) mostly affected the city of Mitilini of Lesvos Island while the Gulf of Edremit-Ayvacık earthquake (M _S = 6.8) largely affected the northern and eastern coastal areas of the Gulf of Edremit. In 1944 earthquake, numerous surface cracks and water gushes were reported. The coastal neighborhoods of the town of Ayvalık in the east were flooded by tsunami waves. At the WSW extend of the main fault observed on land, which is parallel to the present-day slip vectors, some normal-oblique faults were observed close and subparallel to the northern coast. On the basis of historical documents, reports, interviews, geological setting, field observations and marine seismic reflection data, the 1944 earthquake was not triggered by one of the main fault segments but by a secondary fault or fault group which was described in this study. Depending on the distribution of tensional and compressional forces in the region, which rotates clockwise under the control of the middle strand of the North Anatolian fault, secondary fault groups become important. The moment tensor parameters of such small-size events have been determined and have obtained consistent results with the faults proposed in this study.     

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.     

Combination of double couple and non-double couple events during the Van,Turkey, 2011 earthquake sequence

A combination of double couple (DC) and non-double couple (non-DC) earthquakes hit Eastern Turkey, in the vicinity of Lake Van, in October–November 2011. Teleseismic waveform inversion was used to find the best fitting double couple and deviatoric moment tensors on four large and medium sized events of this sequence. The aftershocks of the Mw = 7.1, 2011/10/23:10:41 earthquake built a NE–SW aftershock zone where the Mw = 5.7, 2011/10/25 aftershock was located. The Mw = 6.0, 2011/10/23:20:45 event was located around the terminal section of the Mw = 7.1 aftershock zone which might be triggered by this event (aftershocks of this event propagated from W to E to build a W–E aftershock zone where the Mw = 5.7, 2011/11/09 event was located). For these events the calculated best fitting grid search parameters are not very different from GCMT results, but DC components, after deviatoric moment tensor inversion, represent much more difference with GCMT and grid search. The important feature of deviatoric moment tensor inversion is the existence of a notable compensated linear vector dipole (CLVD) component on the Mw = 5.7, 2011/10/25:14:55 and Mw = 5.7, 2011/11/09:19:23 aftershocks. According to the regional seismotectonics, these CLVD components could be related to crustal rheology and volcanic activities. Based on the results, the existence of a cylindrical aftershock distribution could be taken as an indication of induced seismic activity on complex-ring structures resulted from magma or water–magma injection. However, the existence of Karst like structures suggests that the CLVD components may be under the influence of high-pressure water or gas injection rather than magma.     

Pushover and nonlinear time history analysis evaluation of a RC building collapsed during the Van (Turkey) earthquake on October 23, 2011

The nonlinear seismic behavior of a collapsed reinforced concrete (RC) residential building in the city of Van in Turkey is investigated by the static pushover and nonlinear time history analyses. The selected RC structure was designed according to the 1975 version of Turkish Earthquake Code (TEC-1975). The building had experienced heavy damage, and it was demolished in the Van earthquake on October 23, 2011. The 2007 version of Turkish Earthquake Code (TEC-2007) is considered for the assessing seismic performance evaluation of the selected RC building. The RC structure presents collapse performance level under the earthquake loads. Besides, the analytical solutions show that different performance levels for the sections are obtained from the pushover and nonlinear time history methods.     

Structural damages of the May 19, 2011, Kütahya–Simav earthquake in Turkey

Reconnaissance observations are presented on the building damage caused by the May 19, 2011, Kütahya–Simav earthquake in Western Turkey as well as an overview of strong ground motion data recorded during the earthquake is given. According to Disaster and Emergency Management Presidency of Turkey, the magnitude of the earthquake is 5.7 in local magnitude scale. Although the earthquake can be regarded as a moderate event when considering its magnitude and strong motion recordings, it caused excessive structural damage to buildings in Simav district and several villages in the near vicinity. During the field investigation, different types of structural damage were observed mainly in the reinforced concrete frame buildings with infill walls and masonry buildings with various types of construction materials. Observed damage resulted from several deficiencies in structural and non-structural components of the buildings. Poor construction materials and workmanship, non-conforming earthquake-resistant design and construction techniques and non-ductile detailing are the main reasons for such an extensive damage, as observed in many past earthquakes in Turkey.     

Assessment of the statistical earthquake hazard parameters for NW Turkey

We performed a probabilistic analysis of earthquake hazard input parameters, NW Turkey covers Gelibolu and Biga Peninsulas, and its vicinity based on four seismic sub-zones. The number of earthquakes with magnitude M ≥ 3.0 occurred in this region for the period between 1912 and 2007 is around 5130. Four seismic source sub-zones were defined with respect to seismotectonic framework, seismicity and fault geometry. The hazard perceptibility characterization was examined for each seismic source zone and for the whole region. The probabilities of earthquake recurrences were obtained by using Poisson statistical distribution models. In order to determine the source zones where strong and destructive earthquakes may occur, distribution maps for a, b and a/b values were calculated. The hazard scaling parameters (generally known as a and b values) in the computed magnitude–frequency relations vary in the intervals 4.28–6.58 and 0.59–1.13, respectively, with a RMS error percentage below 10 %. The lowest b value is computed for sub-zone three indicating the predominance of large earthquakes mostly at Gelibolu (Gallipoli) and north of Biga Peninsula (southern Marmara region), and the highest b value is computed for sub-zone two Edremit Bay (SW Marmara region). According to the analysis of each seismic sub-zone, the greatest risk of earthquake occurrence is determined for the triangle of Gelibolu–Tekirda? western part of Marmara Sea. Earthquake occurrence of the largest magnitude with 7.3 within a 100-year period was determined to be 46 % according to the Poisson distribution, and the estimated recurrence period of years for this region is 50 ± 12. The seismic hazard is pronounced high in the region extending in a NW–SE direction, north of Edremit Bay, west of Saros Bay and Yenice Gönen (southern Marmara region) in the south. High b values are generally calculated at depths of 5–20 km that can be expressed as low seismic energy release and evaluated as the seismogenic zone.     

New field and seismic data about the intraplate strike-slip deformation in Van region,East Anatolian plateau,E. Turkey

The study area is the Van earthquake region. It is located in the western section of the East Anatolian–Iranian plateau outside and to the east of the Karlıova triple junction. Based on the tectonic periods, the rock units exposed in the study area are classified into two common categories. These are the Pre-Late Pliocene paleotectonic units and the Plio-Quaternary neotectonic units. The Paleotectonic units are composed of the Yüksekova Complex of Campanian–Maastrichtian age and the Kırkgeçit Formation of Oligo-Miocene age. The paleotectonic units are intensely deformed (folded, thrust to reverse faulted and converted into an imbricate stack). The neotectonic units are composed of fluvio-lacustrine sedimentary facies with volcanic interclations. It is full of soft-sedimentary structures such as deltaic structure, slump fold, sand dikes to sills and normal to reverse types of growth faults which imply to a sedimentation accompanied by both a volcanic activity and active tectonics. Originally the Paleotectonic units are overlain with an angular unconformity by the nearly flat-lying neotectonic units. This angular unconformity and the big difference in the deformational patterns of both categories of rock units indicate an inversion in tectonic regime in Late Pliocene. The new tectonic regime is the strike-slip faulting-dominated neotectonic regime. It is governed by an approximately N–S-directed compression, and composed of NW- to NE-trending strike-slip faults, N–S trending oblique-slip normal faults to fissures and the E–W trending thrust to reverse faults. Most of thrust to reverse faults are inherited from the Pre-Late Pliocene paleotectonic regime. Some of them have reactivated and led to the occurrence of large and devastative earthquakes. The last devastative seismic event is the 23 October 2011 Tabanlı (Van) earthquake of Mw = 7.2 that caused 644 deaths and moderate to heavy damage of ¼ of structures (28,532) in Van earthquake region. The source of the Tabanlı earthquake is the Everek erosional reverse fault. In addition the Tabanlı earthquake is the largest seismic event occurred till now in Turkey. It was followed by a series (over 6000) of small-sized aftershocks and severeal moderate-sized indepentent earthquakes of reverse, normal and strike-slip faulting origin. Both the field and new seismic data strongly reveal that the prominent tectonic regime in the East Anatolian plateau is the strike-slip neotectonic regime, not the tensional tectonic regime as has been reported in some previous works. The strike-slip faulting and related deformation are confined into the upper shallowing part (up to 40 km) of the crust, whilst the extensional deformations are the subcrustal processes and being taking place in a squashy zone at the depths of approximately 40–60 km.     

The van earthquake on October 23, 2011: Natural and technogenic causes

A measurable effect of mass bombing on weak to moderate seismicity, endogenous microseism intensity, and acceleration of tectonic processes has been found. This effect is seen in the regime of strong and catastrophic earthquakes, a decrease in magnitude and time for their preparation, and lesser seismic hazard. The M = 7.8 Van Earthquake on October 23, 2011, was induced to occur early due to mass bombing in Libya and other regions of North Africa; however, the induced character caused its magnitude to be less by several tenths than it might have been.     

Evolution of Çamlık fissure-ridge travertines in the Başkale basin (Van,Eastern Anatolia)

Fissure-ridge travertines (FRTs) are of great importance for the determination and comparison of tectonic deformation in a region. The coeval development of these travertines with active fault zones supplies significant information about regional dynamics in terms of deformation pattern and evolution. In this paper, the characteristics of FRTs of the Ba?kale basin (eastern Turkey) and responsible regional tectonism are discussed for the first time. The Ba?kale basin is located between the Ba?kale Fault Zone (BFZ) characterised by Çaml?k fault and I??kl?–Zirani? fault. It is located between dextral Yüksekova Fault Zone and southern end of dextral Guilato–Siahcheshmeh–Khoy Fault system (Iran). Various morphological features indicating recent activity are exposed along the BFZ, including offsetting rivers, fissure-ridge travertine and fault scarps. The Çaml?k fissure-ridge travertine composing of three different depositions is observed along the eastern edge of the BFZ with approximately parallel orientations. The Çaml?k fissure-ridge travertine has been formed and developed on fault zone related to strike-slip or oblique movements. We explain how kinematic changes of faults can influence the fissure-ridge development.     

Evaluations on the relation of RC building damages with structural parameters after May 19, 2011 Simav (Turkey) earthquake

An earthquake has struck Simav, Kutahya, located in the western part of Turkey on May 19, 2011. This paper focuses on the evaluation of the regional damage data and detailed investigation on a set of selected reinforced concrete buildings in Simav county center. The soil properties in Simav are examined in detail using multi-channel analysis of surface wave measurements, boreholes and laboratory test data. The damages are observed to be independent of soil conditions being hilly or plain, both in regional and Simav county center level. However, a slight relation is observed: as the soil period increases, so does the damage. The most damaged buildings are the four story buildings, resembling the case after some other earthquakes in Turkey. Regarding the detailed numerical evaluations on the building set, the properties highly correlated with seismic damage are investigated. Based on the obtained findings, it is concluded that the global building properties may not be enough to establish a strong relation with damage due to the local damages at the structural member level, especially for smaller seismic events.     

Novel applications of fluid inclusions and isotope geochemistry in unravelling the genesis of fossil travertine systems

The Denizli Basin is a fault‐bounded Neogene–Quaternary depression located in the Western Anatolian Extensional Province, Western Turkey. The basin is a unique geological site with abundant active and fossil (Quaternary) travertine and tufa deposits. Fluid inclusion microthermometry and isotopic analysis were applied to study the genesis of the Ball?k fossil travertine deposits, located in the south‐eastern part of the basin. Microthermometry on fluid inclusions indicates that the main travertine precipitating and cementing fluids are characterized by low salinity (<0·7 wt% NaCl equivalent) and variable temperatures that cluster at <50°C and ca 100°C. Fluids of meteoric origin have been heated by migration to the deeper subsurface, possibly in a local high geothermal gradient setting. A later uncommon cementation phase is related to a fluid with a significantly higher salinity (25·5 to 26·0 wt% bulk). The fluid obtained its salinity by interaction with Late Triassic evaporite layers. Strontium isotopes indicate that the parent carbonate source rock of the different travertine precipitates is very likely to be the Triassic limestone of the Lycian Nappes. Carbon isotopes suggest that the parent CO₂ gas originated from thermal decarbonation of the Lycian limestones with minor contributions of magmatic degassing and organic soil CO₂. Oxygen isotopes confirm the meteoric origin of the fluids and indicate disequilibrium precipitation because of evaporation and degassing. Results were integrated within the available geological data of the Denizli Basin in a generalized travertine precipitation model, which enhanced the understanding of fossil travertine systems. The study highlights the novel application of fluid inclusion research in unravelling the genesis of continental carbonates and provides several recommendations for hydrocarbon exploration in travertine‐bearing sedimentary basins. The findings suggest that travertine bodies and their parent carbonate source rocks have the potential to constitute interesting subsurface hydrocarbon reservoirs.