The light transmission and seiche depth of Izmir Bay,western Turkey

Izmir Bay is one of the most polluted estuaries in the whole Mediterranean Sea. The inner part of the Bay (Inner Bay) is heavily affected by domestic and industrial discharge. As a result of these loads, strong eutrophication occurs in the Inner Bay, which is temporally anaerobic. The ecologically sensitive approach of the local authorities during the last decade has given rise to a wide variety of monitoring and research studies on this bay. On the other hand, the municipality of Izmir started to operate wastewater treatment facilities since January 2000. The Institute of Marine Sciences and Technology — Izmir (IMST) with its research vessel R/V K Piri Reis has been conducting an intensive monitoring program since 1988 and especially during the recent few years. These investigations provide an opportunity for the evaluation of the performance of the wastewater treatment plant in terms of the change in the optical properties of Izmir Bay water in a positive manner. The turbidity values measured in these monitoring studies indicate that the values have changed drastically after January 2000. Their spatial variation indicates that the values decrease from the Inner Bay towards the Aegean Sea. The turbidity (light transmission) values are measured with an automatic CTD (conductivity, temperature and depth) system during each cruise. The seiche disc depth measurement is carried out only occasionally. The accuracy of the seiche disc depth is dependent on certain daylight conditions and depends on the operator. The seiche disc depth (D _s) is an important parameter to estimate primary production of organic matter (hereafter called production). A relation between light transmission (turbidity) value and seiche disc depth (D _s) is found with very good agreement. The correlations are very high (approximately 0.94) with slight seasonal variation.     

Seismic risk assessment of buildings in Izmir,Turkey

Izmir, the third largest city and a major economic center in Turkey, has more than three million residents and half million buildings. In this study, the seismic risk in reinforced concrete buildings that dominate the building inventory in Izmir is investigated through multiple approaches. Five typical reinforced concrete buildings were designed, modeled and assessed for seismic vulnerability. The sample structures represent typical existing reinforced concrete hospital, school, public, and residential buildings in Izmir. The seismic assessments of the considered structures indicate that they are vulnerable to damage during expected future earthquakes.     

曹华峰，韦昌富 饱和局部非均匀土的孔隙水压力动态响应分析

饱和局部非均匀土在动载作用下力学响应的研究一直是动力学领域的难点,如何描述非均匀介质的局部结构,衡量其对宏观孔压产生和消散的影响,目前尚无成熟的理论模型和分析方法。基于有关局部非均质土波动理论的最新研究成果,建立能够描述局部结构对孔压增长和消散过程影响的动力学模型。针对周期荷载作用下的一维饱和岩土层,获得孔隙水压分布的解析解。分别以松弛时间和荷载频率为变量,定量地分析这两个参数对孔隙水压发展的影响趋势,并确定两者对孔压发展的敏感区间,以上述分析为基础,提出对应孔压极值时松弛时间和荷载频率的关系曲线。分析结论对非均匀饱和土动力学的理论研究和工程应用有一定价值。     

Effect of soil layering on the ground response parameters: a parametric study

Soil layering has a pivotal role on the behavior and propagation of seismic waves, hence the ground response during seismic loading. Parametric study to estimate the effect of soil layering on ground response parameters is of prime importance considering the engineering significance of structure founded in seismic zone; nonetheless, it is yet to be well understood. The objective of this study was to investigate the effect of soil layering and soil properties on the ground response parameters. One-dimensional linear ground response analysis was conducted with variation in soil layer parameters including impedance ratio (?? _z ), layer thickness (d _r ), and damping ratio (D). The acceleration time history of the Bhuj Earthquake (M _w ?=?7.7), India, was used in the analysis. The results obtained from the analysis were presented as variation of ground response parameters such as spectral acceleration (SA), amplification ratio (M) with the soil layer parameters. Results showed higher values of SA at lower D and then decreased with increase in D, that in fact depict the resistance offered to the particle oscillation at comparatively higher values of D. Similarly, variation in SA and M was very less or negligible when the ?? _z was varied from 1 to 3 and the d _r equal to 0.2, while for d _r greater than 0.2 the variation increased with ?? _z and d _r . The outcome from the parametric study presented in this paper clearly demonstrates the significance of ?? _z , D, and d _r of the soil layers on the ground response parameters.     

渤海湾西岸风暴潮:叠加地质因素的新探讨

通过对渤海湾西岸1895年以来11次风暴潮高水位的厘定,证实并确定了50年、100年、200年直至10000年一遇的风暴潮高水位值。定量评估了风增水与波浪对风暴潮高水位的贡献。进一步从地学角度讨论了21世纪10年间隔的海面上升量、地面下沉与围海造陆共同作用、海面上升引发的净增水效应及河口增水效应。根据上述各类参数,预测了至2050年的10年间隔、50~10000年不同重现期的极端水位,并讨论了地面下沉对风暴潮测量准确性的影响。认为当前的防潮堤(海垱)高度可抵御50~100年一遇的风暴潮的侵袭,但据所讨论的综合因素的影响,建议2020年防潮堤的高度应达到+4.8m,2030年达到+5.1m(85高程)。     

上海软土动力参数变异性对土层地震反应的影响

应用模态摄动法求解水平分层均匀土层的地震反应，通过大量的数值计算，讨论上海软土土性变化对土层基本周期和表面地震加速度反应的影响。数值结果表明：准确获取土层的动力参数对土层地震反应计算有重要影响，在现场实测获得较为翔实的土样动力特性参数的基础上，土层土性动力参数变异性所产生的计算误差是有限的。     

Influence of gold mine on groundwater quality (Efemçukuru, Izmir, Turkey)

. Currently, exploration of gold ores is under discussion in Turkey, without considering its adverse affect on the environment. Studying the adverse affect on environment is extremely important because significant civic activities are already taking place on the geological units that contain gold ore bodies in Turkey. Such an area is located at the southeast of Izmir City (Turkey), and approximately 2-km-long gold-bearing ore veins occur close to the Efemçukuru Village. The objective of this study was to describe the characteristics and seasonal variation of the groundwater chemistry and pollution of the aquifer in the ore deposit site, and to determine the impact of ore deposits on groundwater quality. The gold-bearing formation is highly weathered and fractured. The fractures in the geological units control the permeability and the depth of groundwater in the area. The concentrations of Al, Ag, Cu, Cd, Cr, Fe, Pb, Mn, Zn, Ni, and Sb were determined for four well samples and two stream waters for wet and dry seasons. The results showed that the concentrations of most of these elements were below the USA EPA (Environmental Protection Agency) limits; however, Pb and Cd concentrations are slightly above the limits. The results indicate that minerals in gold bodies do not dissolve although the weathering of formations is high. The low concentration of elements in groundwater and streams may be attributed to the high velocity of ground and surface water.     

Estimation of ground response and local site effects for Vishakhapatnam,India

Natural Hazards - Ground motion intensity due to an earthquake changes as it disseminates through the soil media from bedrock to the surface. As the ground motion intensity and damage levels mainly...     

渤海湾西北岸全新世牡蛎礁研究概述

环太平洋西岸,特别是渤海湾西北岸沿海平原全新世地层中广泛分布着由Crassostrea gigas牡蛎形成的礁体。总结了渤海湾西北岸30余年来众多研究者的主要成果。论述了C秘的定名沿革、生态习性、礁体特征、礁体与海面的关系。测定了C萌秘壳体的^18O和^13C同位素组成,发现了壳体生物碳酸钙的年际变化律,结合可靠的^14C数据,建立了正常建礁与个体分泌壳体之间的线性函数关系（约1cm／a）、水平夹层的平均历时（约200a,／层）等定量参数,进而提出“礁体历时假说”,并将该地区时间跨度约7750-950calBP的化石牡蛎礁划分为8道礁群,论证了礁体内部水平夹层和礁体之上泥质“转换层”可能记录的百年尺度的“缓变型”环境变化。     

渤海湾西岸全新世沉积速率对河流供给的响应

渤海湾西岸由北向南获取了3个钻孔,以全新世海相岩心为研究对象,采用AMS14C(Accelerator Mass Spectrometry14C,加速器质谱14C)测年方法建立年代框架并计算平均沉积速率,结合沉积物粒度组成及沿岸古河流三角洲发育历史,探讨了沉积速率对沿岸河流供给变化的时空响应。结果表明,早全新世—中全新世初期(11~6ka),渤海湾西岸整体沉积速率偏低,仅0.03~0.07cm/a,沉积物粒度较粗;中全新世6.43~4.97ka cal BP期间,NP3孔平均沉积速率为0.60~0.93cm/a,高于同期沿岸南部的CH110孔和BT113孔。沉积物组成以粉砂为主,粘土含量低,向上逐渐变粗,具三角洲反粒序特征。该时段的高沉积速率系渤海湾西北岸对潮白河、永定河及滦河沉积物供给的响应;中全新世晚期3.68~2.67ka cal BP期间,BT113孔沉积速率为0.27~1.4cm/a,高于同期沿岸北部CH110孔和NP3孔,沉积物组成以粉砂为主,粘土含量较NP3孔高,向上逐渐变粗,具三角洲反粒序特征。该时段的高沉积速率系渤海湾西岸南部对黄河沉积物供给的响应;晚全新世2.29~0.24ka cal BP期间,沿岸中部CH110孔沉积速率为0.55~0.91cm/a,高于同期沿岸南部的BT113孔和北部的NP3孔,该高沉积速率为渤海湾西岸中部对黄河和海河供给沉积的先后响应。     

碎石土斜坡水平受荷桩承载特性研究

斜坡上的桩基础的承载性能是复杂多变的。对于四川西部山地地形较广泛,且地基覆盖层多为特有的碎石土地层来说,水平受荷桩的相关研究还较少。为了研究碎石土地基斜坡上单桩基础的水平承载特性及桩土间的相互作用,通过现场水平静载荷试验在坡度为0°、15°、30°、45°的条件下,探讨桩身变形、桩身弯矩、土压力的变化。运用FLAC3D有限元分析软件得出水平荷载作用下,碎石土斜坡不同坡度的桩基础与桩周土之间的应力云图、位移云图的变化特点。将数值模拟结果与现场试验结果进行了对比,提出了单桩水平临界荷载和极限荷载在不同坡度区间内取值时的折减系数,为实际工程提供一定的参考。     

Hydrology,hydrogeology and hydrochemistry of wetlands: a case study in Izmir Bird Paradise,Turkey

Izmir Bird Paradise is one of the most valuable wetlands in Turkey, but this area is now being threatened by the drying out of marshes and water pollution. This wetland consists of two ecosystems: fresh- and saltwater. The recharge of marshes is from rainfall, the Gediz River and groundwater from Can Suyu Pond. The water type of the river is Ca-Mg-Na-HCO₃-SO₄, whereas the groundwater is a Na-Cl water type. The reasons for the drying are long-term drought (evapotranspiration at 894 mm is >> rainfall at 546 mm), and excessive pumping of groundwater and seawater intrusion into Menemen Plain. Therefore, an additional freshwater resource is necessary. This water can be supplied from the limestone levels of Neogene sedimentary rocks in and around Izmir Bird Paradise that have a Ca-HCO₃ water type. Water pollution levels were also analysed. In the freshwater ecosystem Cd, Cr, Fe, Mn, Ni, Pb, Sb and Zn values, in the open channel in Izmir Bird Paradise Sb, Fe, Ni and Cd values, and in the river Fe, Pb and Sb values exceed the TSE 266 and EPA 2000 standards probably due to agricultural and industrial sources.     

Controls on nutrient and phytoplankton dynamics during normal flow and storm runoff conditions, southern Kaneohe Bay, Hawaii

Fluvial effects on nutrient and phytoplankton dynamics were evaluated in southern Kaneohe Bay, Oahu, Hawaii. Fluvial inputs occurred as small, steady baseflows interrupted by intense pulses of storm runoff. Baseflow river inputs only affected restricted areas around stream mouths, but the five storm events sampled during this study produced transient runoff plumes of much greater spatial extent. Nutrient loading via runoff generally led to an increase of the phytoplankton biomass and gross primary productivity in southern Kaneohe Bay, but the rapid depletion of nutrients resulted in a decline of the algal populations in the relatively short time of days. Under baseline conditions, water column primary productivity in southern Kaneohe Bay is normally nitrogen limited. Following storm events, the high ratio of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIN:DIP, 25–29) fluxes of runoff nutrients drove bay waters towards phosphorus limitation. A depletion of phosphate relative to DIN in surface waters was observed following all storm events. Due to high flushing rates, recovery times of bay waters from storm perturbations ranged from 3 to 8 d and appeared to be correlated with tidal range. Storm inputs have a significant effect on the water column ecosystem and biogeochemistry in southern Kaneohe Bay. The perturbations were only transient events and the system rapidly recovered to prestorm conditions.     

河北平原典型地裂缝场地动力响应特征研究

河北平原地裂缝分布广泛、致灾严重,给当地工程建设和人民生活造成了严重影响。目前对于河北平原地裂缝的研究主要是发育特征、成因机理以及分布等方面,对该区域场地动力特性的研究不足。为讨论河北平原地裂缝对场地动力响应的影响,分别选取该地区具有代表性的地裂缝(高丽营地裂缝和隆尧地裂缝(构造成因)、大名地裂缝(古河道成因)、唐山地裂缝(地震成因))进行野外地脉动测试,并通过傅里叶谱分析、反应谱分析和Arias烈度分析,揭示了不同类型地裂缝场地的动力响应特征。结果表明,地裂缝对场地卓越频率和卓越周期的影响较小,但对场地动力响应强度的影响较大。在地裂缝附近区域具有放大效应,上盘放大倍数达到2.2~2.7,下盘放大倍数达到1.7~2.4,并随着与地裂缝距离的增大逐渐衰减,一定距离后趋于平稳,且活动性更强的上盘的放大效应更明显。不同类型地裂缝对场地动力响应的影响趋势基本一致,但影响范围不同:构造地裂缝场地的放大效应影响范围最大,约24 m,地震地裂缝次之,约22 m,古河道地裂缝最小,约20 m。综合考虑河北平原地裂缝对场地影响范围:上盘约24 m,下盘约20 m。场地放大效应及其影响范围可以为河北平原地裂缝场地工程结构的合理抗震设防提供依据。      

基于神经网络的大连东北海岸带碎石土地基强夯加固研究

以大连某实际工程作为研究场地,室内试验与原位测试所得碎石土地基物理力学参数与实测所得强夯处理沉降量作为样本,通过BP神经网络对样本的训练、学习,建立地基土力学参数与强夯处理的沉降量之间的映射关系,利用所得映射关系对场地实测的沉降量进行物理力学参数的反演分析。结果表明:经过训练的神经网络模型可快速得出所需参数,利用flac3d以反演所得参数进行计算,模拟沉降量与实测沉降量的误差为4.87%,在可接受的范围之内;基于神经网络的位移反分析方法可以省去繁琐的测试工作,但该方法的实现需要有充足的样本数据作为支撑。     

福建沿海地区场地土对地脉动动力响应的研究

以福建省泉州市区和福州市区场地土的动力特性和地脉动频谱结构为研究对象,通过对这两个地区的地脉动信号的频谱分析获得频谱结构特征,由此来深入研究该地区岩土的动力特性及场地土层的地脉动动力响应。通过场地脉动的测试,利用快速傅立叶变换(FFT)方法对观测到的地脉动信号进行频谱分析。根据实际观测资料研究了地脉动频谱结构特征及场地土对地脉动的频率响应的特性。研究不同地基土层构造与地脉动的频率依赖以及频率选择作用。结果表明,地脉动的频谱特性与场地覆盖层厚度和地基土刚度的变化密切相关;覆盖层厚度是影响地脉动卓越周期的重要原因,其中软土层对地脉动的卓越周期有一定的放大作用。     

地震动强度对斜坡加速度动力响应规律的影响

依托大型振动台试验成果,采用加速度响应峰值PGA及其放大系数相结合的分析方法,系统地探讨了上硬、下软和上软、下硬两种岩性组合结构斜坡模型,分别在正弦波和天然地震波作用下坡面各高程点的水平向和竖直向加速度响应随震动强度增大的变化规律。试验结果分析表明：①在天然波作用下两斜坡模型的水平向和竖直向PGA均随震动强度增大而增大,而放大系数则随震动强度增大到一定程度时,逐渐减小并趋于稳定;②在正弦波作用下两斜坡模型的水平向和竖直向PGA亦随震动强度增大而增大,然而竖直向PGA放大系数随震动强度增大亦有所增大,说明竖直向加速度响应表现出了相对于水平向响应较弱的非线性特征;③在水平向和竖直向地震力作用下加速度响应沿高程表现出的放大效应分别体现在斜坡模型的上段和下段。此外,斜坡模型的加速度响应沿坡面在坡脚、坡中和坡肩等特殊部位出现了多个极值区;④在水平向地震力作用下低频的地震波作用要强于高频地震波,且加速度在上硬、下软岩性组合结构斜坡模型中的响应要强于上软、下硬岩性组合斜坡模型;在竖直向地震力作用下则呈现相反结果。其研究结果对高地震风险山区的防震减灾及灾后重建都具有指导和借鉴意义。     

A millennial-scale record of Holocene tsunamis on the Kronotskiy Bay coast, Kamchatka, Russia

Deposits from as many as 50 large tsunamis during the last 7000 years are preserved on the Pacific coast of the Kamchatka Peninsula near the mouth of the Zhupanova River, southern Kronotskiy Bay. These deposits are dated and correlated using Holocene marker tephra layers. The combined, preserved record of tsunami deposits and of numerous marker tephras on Kamchatka offers an unprecedented opportunity to study tsunami frequency. For example, from the stratigraphy along southern Kronotskiy Bay, we estimate frequency of large tsunamis (>5 m runup). In the last 3000 years, the minimum frequency is about one large tsunami per 100 years, and the maximum about one large tsunami per 30 years; the latter frequency occurred from about 0 to 1000 A.D. This time interval corresponds to a period of increased seismicity and volcanic activity that appears to be recorded in many places on the Kamchatka Peninsula.     

Deterioration of the volcanic kerb and pavement stones in a humid environment in the city centre of Izmir, Turkey

?zmir is the third largest city in Turkey and has being the centre of art, culture, tourism and trade activities throughout the 5,000 years of its history. Natural stones brought from different parts of the world have been widely used for construction of the prestigious buildings, monuments and roads etc., in the past in the city. Renovation of the street pavements and public gathering areas in the city centre has been undertaken by the Metropolitan Municipality in 2000 and continued through the year of 2001. These renovation activities have mainly been carried out in the streets running parallel to the sea shore. Volcanic rocks brought from the Central Anatolia Ankara-Gölba?? (andesites) and Kayseri-?ncesu (tuffs) have been used in the renovation works. These rocks have shown extensive deteriorations within 4 years of their usage between 2001 and 2005 under the influence of different environmental factors. In this study, the deteriorations developed in the recently placed volcanic rocks used as kerb and pavement stones in the city centre of ?zmir in the light of their mineralogical, chemical, physical and mechanical properties, used locations and the environmental factors are presented.