Near Source Effects and Engineering Implications of Recent Earthquakes in Turkey

The variation of both structural and geotechnical consequences of near-source effects are shown for densely populated environments, Kocaeli and Düzce (Turkey), situated on an alluvial fan at the western part of the 1500 km long North Anatolian fault (NAF) that resembles the San Andreas fault in California with its right-lateral and strike slip faulting mechanism as well as remarkably similar length and capability of generating damaging earthquakes. Recordings from two recent destructive earthquakes occurred in 1999 on the NAF suggest that nearsource impulse type ground motions may generate large input energy demands that have to be dissipated with few large displacement excursions. The discussion is therefore focused on the seismic wave propagation mechanism related to the unexpected damages at the nearfield sites. The observation results proved the high intensity velocity at the damage suffering areas due to the soil layer resonance and, furthermore, due to the bump effect by wave interferences traveling vertically and horizontally. While there are potentially other factors contributing to damage (such as topographic and basin effects, liquefaction, ground failure, or structural deficiencies), the amplification of ground motion due to local site conditions plays an important role in exacerbating the seismic damages in disaster belt area. The field observations regarding this phenomenon supplemented with the near-field strong motion interpretations are presented, and significance of local soil effects in the near-field region is assessed in the course of this study

Seismic Response on Dense and Loose Sand Columns

Densification (Compaction) of loose saturated soils has been the most popular method of reducing earthquake related liquefaction potential. Compaction of a foundation soil can be economical when limited in extent, leading to a case of an “island” of improved ground (surrounded by unimproved ground). The behavior of the densified sand surrounded by liquefied loose sand during and following earthquakes is of great importance in order to design the compacted area rationally and optimize both safety and economy. This problem is studied herein by means of dynamic centrifuge model tests. The results of two heavily instrumented-dynamic centrifuge tests on glycerin-water saturated models of loose and dense sand, prepared adjacent to each other are discussed. Observed model response provided an improved understanding of dynamic liquefaction behavior of a densified ground surrounded by a loose liquefiable ground. The test results suggest the following concerns about “Islands” of densified soil: 1) there is a potential strength loss in the densified zone as a result of pore pressure increase due to migration of pore water (or fluid) into the island from the adjacent (loose) liquefied ground; 2) there is a potential for lateral deformation (sliding) within the densified island as the surrounding loose soil liquefies

Liquefaction During the October 12, 1992, Egyptian Dahshure Earthquake

On October 12, 1992 a moderate earthquake MB = 5.9 (MS = 5.2) occurred about 18 km southwest of the center of Cairo and resulted in significant damage to numerous poorly constructed structures. Soil liquefaction associated with the occurrence of large sand-boils was observed close to the epicenter. As a consequence, a main road suffered a maximum settlement of about 1.75 m. In this study, the earthquake characteristics, soil profiles and resulting liquefaction are discussed. The observed liquefaction mechanisms provide valuable information on the seismic response of Nile deposited alluvial soils. Such soils constitute much of the inhabited area of Egypt

Behavior of Reinforced Wall System During the 1999 Kocaeli (Izmit), Turkey, Earthquake

A four-span bridge together with a 10 m-high and 100 m-long bridge approach fill was one of the highway facilities damaged due to surface faulting along the Trans-European Motorway during 1999 Kocaeli Earthquake (Mw 7.4). The fault rupture crossed beneath an overpass bridge within a few meters away from the bridge abutment while damaging the approach fill which was reinforced with a double-faced mechanically stabilized earth wall (MSEW) system. The faulting-induced excessive tectonic ground deformations including near-field seismic shakings were the main sources of damage in the walls. Such effects, along with the others, caused cracks and panel separations in wall faces as a result of a liquefaction-induced differential settlement in the cross section. The performance of the reinforced walls was satisfactory that there was no significant structural damage despite the total collapse of the bridge decks. The wall system provided a unique case history under extreme loading conditions, while proving that they are flexible and can withstand large ground deformations. This paper discusses how the walls performed based on post-earthquake reconnaissance studies. The faulting activity, geology of the site, strong ground motions and damage states in the reinforced wall are discussed in details

Internet and gaming addiction: a systematic literature review of neuroimaging studies

In the past decade, research has accumulated suggesting that excessive Internet use can lead to the development of a behavioral addiction. Internet addiction has been considered as a serious threat to mental health and the excessive use of the Internet has been linked to a variety of negative psychosocial consequences. The aim of this review is to identify all empirical studies to date that used neuroimaging techniques to shed light upon the emerging mental health problem of Internet and gaming addiction from a neuroscientific perspective. Neuroimaging studies offer an advantage over traditional survey and behavioral research because with this method, it is possible to distinguish particular brain areas that are involved in the development and maintenance of addiction. A systematic literature search was conducted, identifying 18 studies. These studies provide compelling evidence for the similarities between different types of addictions, notably substance-related addictions and Internet and gaming addiction, on a variety of levels. On the molecular level, Internet addiction is characterized by an overall reward deficiency that entails decreased dopaminergic activity. On the level of neural circuitry, Internet and gaming addiction led to neuroadaptation and structural changes that occur as a consequence of prolonged increased activity in brain areas associated with addiction. On a behavioral level, Internet and gaming addicts appear to be constricted with regards to their cognitive functioning in various domains. The paper shows that understanding the neuronal correlates associated with the development of Internet and gaming addiction will promote future research and will pave the way for the development of addiction treatment approaches

Pre-failure instability of sand under dilatancy rate controlled conditions

Experimental results are presented in this paper to show that a runaway type of pre-failure instability can occur for sand under dilatancy rate controlled conditions when an appropriate strain increment ratio, dεv/dε1, is imposed. This type of instability is similar to the runaway type of instability observed for very loose sand under undrained conditions. Whether a soil element will undergo pre-failure instability depends on the difference between the strain increment ratio of the soil obtained from drained test, under a specified effective confining pressure, (dεv/dε1)s, and the strain increment ratio imposed during the test, (dεv/dε1)i, rather than the absolute magnitude of (dεv/dε1)i. Based on the experimental data obtained in this study it was found that an instability line can be determined from a series of strain path tests conducted at different effective confining pressures but with the same dεv/dε1 by joining the peak points of the effective stress paths to the origin in the q–p′ stress space. This line is similar to the instability line obtained from undrained tests on loose sand. The instability tests under dilatancy rate controlled conditions indicate that the stress ratio at the onset of instability obtained in the instability tests coincide with the peak stress ratio line. This suggests that the peak stress line can be used to predict the onset of instability under dilatancy rate controlled conditions in the same way as the use of instability line to predict the onset of instability under undrained conditions

Are Adolescents Engaged in the Problematic Use of Social Networking Sites More Involved in Peer Aggression and Victimization?

The problematic use of social networking sites is becoming a major public health concern. Previous research has found that adolescents who engage in a problematic use of social networking sites are likely to show maladjustment problems. However, little is known about its links with peer aggression and victimization. The main goal of this study was to analyze the relationship between problematic use of online social networking sites, peer aggression ¿overt vs. relational and reactive vs. instrumental¿, and peer victimization ¿overt physical and verbal, and relational¿, taking into account gender and age (in early and mid-adolescence). Participants were selected using randomized cluster sampling considering school and class as clusters. A battery of instruments was applied to 1,952 adolescents¿ secondary students from Spain (Andalusia) (50.4% boys), aged 11 to 16 (M = 14.07, SD = 1.39). Results showed that girls and 14¿16 adolescents were more involved in a problematic use of online social networking sites. Furthermore, adolescents with high problematic use of online social networking sites were more involved in overt¿reactive and instrumental¿and relational¿reactive and instrumental¿aggressive behaviors, and self-reported higher levels of overt¿physical and verbal¿and relational victimization. Even though boys indicated higher levels of all types of victimization, girls with high problematic use of online social networking sites scored the highest on relational victimization. Relating to age, early adolescents (aged 11¿14) with higher problematic use of online social networking sites reported the highest levels of overt verbal and relational victimization. Overall, results suggested the co-occurrence of problematic use of online social networking sites, peer aggression and victimization. In addition, results showed the influence that gender and age had on peer victimization. This study highlights the continuity between offline and online domains with regard to maladjustment problems in adolescence.Departamento de Educación y Psicología SocialVersión del edito

Liquefaction and Ground Failure During the 1998 Adana (Turkey) Earthquake and Lab Model Simulations

Although the June 27, 1998 Adana (Turkey) earthquake event was moderate in magnitude (5.9 on the Richter scale) and in the resulting damage, it contains significant valuable data for geotechnical earthquake engineering. The coincidence of the earthquake epicenter and the fault with a very vulnerable geological surface formation - thick alluvial deposits of Ceyhan River containing loose sand-silt layers, accounted for substantial thickness and area1 distribution of liquefied sediments. Consequently, liquefaction associated ground deformations such as lateral spreading, flow failures, ground fissures and extensional cracking, sand boils, ground subsidence and slope failures were widespread. This paper presents and analyses the liquefaction and associated ground deformations observed during this earthquake. Field data on the occurrence of liquefaction-induced ground failures are used in conjunction with laboratory small-scale model testing results to help to improve our understanding of the mechanisms of generation of several forms of liquefaction-induced ground failure. In this context, valuable observations were made particularly for the sand boiling mechanisms

Vitamin E, Turmeric and Saffron in Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is a growing epidemic and currently there is no cure for the disease. The disease has a detrimental effect on families and will strain the economy and health care systems of countries worldwide. The paper provides a literature review on a few ongoing possible antioxidant therapy treatments for the disease. The paper highlights use of vitamin E, turmeric and saffron for an alternative antioxidant therapy approach. Clinical studies report their therapeutic abilities as protective agents for nerve cells against free radical damage, moderating acetylcholinesterase (AChE) activity and reducing neurodegeneration, which are found as key factors in Alzheimer’s. The paper suggests that future research, with more clinical trials focused on more natural approaches and their benefits for AD treatment could be worthwhile