近岸水平场地液化侧向大变形机理及软化模量分析方法

本文依据震害现象和实验探讨近岸水平场地地面液化侧向大变形机理，改进现有软化模量分析技术，给出一套地面液化侧向大变形的分析方法。近岸水平场地侧向大变形机理因地基中孔隙水压力升高、土体模量衰减、土骨架变软使偏应变得到充分发展所致，其水平永久侧移可用从底部到顶部呈增加形式的整体变形描述。利用本文方法，对1995年阪神地震中近岸沉箱岸壁和土体液化侧向大变形进行了数值模拟，结果与震后实测结果和试验结果在主要特征上一致，说明改进的软化模量法可以用于地面液化侧向大变形的分析。     

Relative influence of physical removal and biodegradation in the depuration of petroleum-contaminated seashore sediments

Two field experiments were conducted for a 21-month period to monitor the fate of an Arabian light crude oil spread on the surface of seashore sediments at low energy sites. The weathering of saturated and of aromatic hydrocarbons followed curvilinear decreasing curves, the saturates being eliminated more rapidly than the aromatics. The asphaltic fraction was more persistent and decreased only very slowly. On the basis of the results, a tentative semi-quantitative graphic model is proposed to evaluate the relative parts of physical removal and of biodegradation in the decontamination of oil-polluted seashore sediments. The model establishes interrelations between the residual concentration of total hydrocarbons (sum of saturates and aromatics), the age of the pollution and the biodegradation stage, defined by capillary gas-chromatography. The biodegradation stage was directly related to the residual level of the oil contamination in the sediments.     

烟台海岸软土场地特征及对地震动参数的影响

本文利用剪切波速和钻孔资料，根据中国GB50011-2001规范、美国FEMA-NEHRP规范、欧洲EUROCODE 8规范，对烟台滨海软土场地类别进行评定。并通过场地地震动效应分析，研究滨海场地土特征对地震动的影响。结果表明，简单的场地类别划分难以反映软土场地的实际情况；滨海软土场地对地震动加速度的幅值和频谱的影响非常明显，其对峰值加速度的放大倍数较高，但受土的非线性变形影响，随地震动输入的增大其放大倍数呈非线性降低；软土场地使得加速度反应谱谱形变宽，特征周期变大。     

天津滨海场地土类别特征及其对地震动的影响

本文按照三种规范(中国建筑抗震设计规范(GBS0011-2001)、美国FEMA-NEHRP规范(2000)、欧洲结构抗震规范(EUROCODE 8,1998)),利用钻孔和剪切波速资料,对天津滨海地区的场地土类别进行研究。通过场地地震动效应分析,研究该场地土对地震动的影响。结果表明,对于滨海场地,简单的场地类别划分难以反映软土场地的实际情况;滨海软土场地对地震动加速度的幅值和频谱的影响非常明显,其对峰值加速度的放大倍数高达1．9,但受土的非线性变形影响,随地震动输入的增大其放大倍数呈非线性降低;软土场地使得加速度反应谱谱形变宽,特征周期变大,变化幅度在0．1s—0．4s。     

Design response spectra for Aqaba City–Jordan

Strong motion records for earthquakes epicentred in the Gulf of Aqaba during swarms in August 1993 and November 1995 are studied. These recordings are made at two sites in the City of Aqaba, one near the seashore and the other inland. The former site has deep alluvial profile with low shear-wave velocity, while the latter's soil profile is constituted of shallow stiff alluvium overlaying rock. The magnitudes of these events range from 4·8 to 6·2 on the Richter scale. Ground motion on the seashore site is much greater than the inland site. Response spectra are derived for each of the available accelerograms. Thirteen records at the inland site are statistically treated to arrive at mean response spectrum using 5 per cent damping. The derived spectra are found to be sharp with small plateau, this is associated with small peak displacement. Empirical site-dependent response spectra are also derived based on recent research and on recommendations of the UBC'97. Comparison is made between the empirical and measured spectra. These were found to be quite close for the inland site but data are not sufficient for the seashore site to make a conclusive comparison. Copyright © 1999 John Wiley & Sons, Ltd.     

大地电场观测深埋铅电极测量系统试验

为使用铅电极替代不极化电极,以解决滨海地区大地电场观测系统稳定性差的问题,先后开展了浅埋的铅电极与不极化电极的大地电场对比观测,以及深埋铅电极与浅埋铅电极的对比观测试验。结果表明:铅电极与固体不极化电极的观测数据在短期内有较好的一致性;深埋铅电极的大地电场观测资料在长期稳定性上优于固体不极化电极;而观测数据的内在观测质量也高于浅埋铅电极。     

台湾海峡架桥铺路的层析技术问题的初步分析

关于在台湾海峡架桥和修筑隧道的问题从1987年至2002年在福省召开过三次"台湾海峡两岸地质地震和架桥与修筑隧道的研讨会",以后陆续出版了相应的论文和论文集,提出了"台湾海峡架桥和修筑隧道的可行性研究",和"台湾海峡隧道工程设计总建议"等[1-4],论述了修建该工程的可行性等问题.提出平潭岛可作为海峡北线的端点,探讨了如何具体建桥和相关工程的问题.近年来地球层析技术的发展,可对台湾海峡隧道工程的工程地质问题,海港的开发和沿海陆地的充分利用等,做出探测台湾海峡地下地层三维成像细结构和地球物理场的空间分布,作为台湾海峡架桥铺路工程基本设计的必要依据.为了让大中小轮船在台湾海峡顺利通航,利用现代的科技研讨台湾海峡两岸连接的最佳方案.为了架成大型的高桥和修建堤坝式的地基,必须用地震层析和应力波等方法探测桥梁和堤坝地基的结构和地层的坚实程度,以便决定桥墩深入海底的深度,和设计坚固而又经济的桥墩与堤坝的基础.参考开采海底石油平台施工和荷兰填海造田的工程经验,以双边海堤与大型高桥及活动的船闸相结合,从平潭岛东至台湾新竹西海岸,在124千米距离上架设4-6段桥梁和5-7段堤坝型的路基,既让大中小船舶照常航行,海洋生物照常游动,又可在其上通车,以缩短两岸距离,适应中国大陆和台湾经济快速发展的需要,争取和平沟通的愿望.由于架桥铺路的工程费用较修筑隧道的投资低得多,在福建近海地带局部填海造地,充分利用海洋资源和建筑深水码头,可得到较大的经济补偿,在现阶段较易实施.本文初步分析了有关的地球层析和工业CT技术的作用问题.     

过渡带拼接地震资料处理方法研究

本文针对滩海过渡带及多个相邻区块资料拼接的工区情况,提出了一系列的解决方案:包括匹配滤波因子的计算、时差的判别、相位差判别,频率匹配,异常能量压制,振幅补偿等联合处理方法,最终很大程度上实现了包括能量差、频率差、时差以及相位差的消除,有效解决了由于滩海过渡带地表条件极其复杂,地震激发、接收环境差、差异大而引起的地震资料分辨率与信噪比低、成像和一致性差的问题.     

华夏地块东南部地壳地震各向异性特征初步研究

本研究采用SAM剪切波分裂分析方法，使用福建区域数字地震台网记录到的（1999年01月～2003年12月）的波形资料，挑选符合剪切波窗口条件的记录，得到华夏地块东南部地区23°N～29°N，116°E～120°E）10个台站的剪切波分裂参数. 研究结果表明，该区域快剪切波平均偏振方向为NW109.4°±42.6°，慢剪切波平均时间延迟为2.5±1.5(ms/km)，快剪切波平均偏振方向对应该区的水平主压应力方向. 闽东台站NW方向的快剪切波偏振优势方向揭示了NW向的水平主压应力和NW走向断裂的构造意义. 两个闽西台站NE方向的快剪切波偏振优势方向与区域水平主压应力方向不一致，与NE走向的断裂一致，体现了局部构造和局部应力场的复杂性. 本研究证实，位于活动断裂上的台站的快剪切波偏振方向的优势方向与断裂走向一致，位于海边或岛上的台站的快剪切波偏振方向较为离散，主要是受到不规则表面地形和断裂交汇的影响. 慢剪切波延迟时间的空间分布特征，显示沿海地区慢剪切波延迟时间变化较大，而内陆地区则较为平缓.     

日本宫崎县石卷平原海啸堆积物调查

2007年4月,为执行科技部科研院所社会公益课题 "中国沿海地区古海啸的定量研究",课题组部分成员访问了日本,并对日本东北地区宫崎县石卷海岸平原的海啸堆积物做了概略性的调查。2011年3月11日,该地区发生了9.0级大地震并引发海啸,造成了巨大的经济损失和人员伤亡。为了使人们对该地区过去的海啸历史有一个概略认识,并了解海啸堆积物的调查方法,对这次调查作一简要报道。这次调查揭示出3次海啸事件,最新一次发生在公元915年十和田火山喷发之前,对应于公元869年的贞观大海啸。     

Delta formation processes at the Mississippi River mouth

Specific processes of delta formation at the Mississippi River mouth are discussed. In the last 7000–8000 years, a series of large deltaic lobes was formed in succession at the Mississippi River mouth under the condition of high river sediment runoff and stabilization of the ocean level after its sudden postglacial rise. In the mid-XX century, the formation of a new deltaic lobe began at the Atchafalaya Branch mouth. Over the last centuries, the processes of delta formation at the Mississippi River mouth slowed down as a result of the river sediment runoff decrease after flow regulation of the Missouri and Arkansas tributaries; in some parts of the deltaic plain, these processes gave way to degradation of marshes and seashore erosion under the impact of intense land subsidence. The current processes of delta formation are under the great influence of local economic activities.     

用剪切波分裂研究台湾北部地壳各向异性

研究主要使用台湾北部13个地震台站记录到的1991年7月～2002年12月的波形数据,采用剪切波分裂SAM分析方法,对台湾北部地区的剪切波分裂特征进行了研究.发现位于宜兰盆地内的台站的快剪切波优势偏振方向为近E-W方向,而位于山脉(西部麓山带、雪山山脉和中央山脉)的台站的快剪切波优势偏振方向为NNE向或NE方向.位于海...     

福建及沿海地区地震活动力源探讨

综合地震震源机制解和地壳形变观测资料的研究, 求得福建及其沿海地区现代震源应力场, 认为这与台湾地区、 台湾海峡应力场相互衔接, 主压应力轴优势方位为NW-SE向, 力轴仰角较小, 应力场近于水平挤压, 形变场反映近期福建沿海亦受北西方向, 接近与海岸垂直的挤压力。 进一步分析该区域内的断裂构造特征和地震活动强度由东至西逐渐减弱的规律, 认为菲律宾海板块与欧亚板块的相互作用力不仅是台湾强震力源所在, 而且其影响向西扩展, 福建及其沿海地区地震活动主要力源仍然是来自这两大板块的相互作用力。     

An experimental study on erodibility of intertidal sediments in the Yellow River delta

The erodibility of intertidal sediments is an important factor affecting coastal erosion.In July and October 2008,in situ measurement of erodibility of the surficial sediment were conducted using a recirculating flume at 20 tidal flat experiment sites along the seashore of the Yellow River delta.At the same time,the characteristics of sand ripples and biogenic features on the tidal flat were observed and the physical-mechanical sediment properties such as bulk density,water content,grain size distribution,plasticity,penetration resistance,shear strength and compressibility,were measured.By field measurement,it is obtained that the critical erosion shear stress of the surficial sediment on the tidal flat varies between 0.088 Pa and 0.254 Pa.The factors influencing sediment erodibility are complicated because of physical and biological reworking after the sediment deposited.There’s a positive correlation between shear strength and critical erosion shear stress.The burrowing crabs’ activities changed the sediment microtopography and made the sediment have greater roughness,and that is one possible reason for the higher erodibility.The formation of scour pits on the tidal flat correlates with the heterogeneous erodibility of the surficial sediment.     

Shoreline spatial and temporal response to natural and human effects in Boujagh National Park,Iran

Shoreline variation and river deltas are among the most dynamic systems in marine environments. The related different variations in spatial and temporal scales play significant roles in land planning and different management applications. Modeling the dynamics of seashore of Boujagh National Park (BNP) which is located on the southern coast of the Caspian Sea in the Sefidrud Delta (SD), considering natural and anthropogenic factors, was the main objective of the current study. To achieve this goal, a combination of remote sensing data, historical data, and numerical simulations was utilized. The BNP covers an area of 3,270 ha and includes two international wetlands, Boujagh and Kiashahr. In earlier periods, this area faced severe morphological changes whereas recently its shoreline has experienced gradual variations. Accordingly, at the first stage, the shoreline variation from 2006 to 2017 was extracted by processing and classifying Operational Land Imager (OLI) and Thematic Mapper (TM) images from Landsat satellites using the Maximum Likelihood approach. In the second stage, the two dimensional MIKE21 model was utilized to identify wave and coastal current patterns and parameters for the year 2015. Morphologically, the results showed that, the shoreline of the BNP is affected by several natural and anthropogenic factors. Seaward advancement of the shoreline occurred in zones A (east zone) and C (west zone) due to Caspian Sea Level drop and sedimentation while retreating occurred at Zone B (north zone) influenced by wave and current patterns and reduction of the Sefidrud River flows. Also, the results imply that maintaining the existing conditions results in the disappearance of a considerable part of the ecological area in the BNP. Hence, to manage and preserve the coastline of the BNP complying with the current anthropogenic and natural factors, it is vital to take necessary management measures.     

Dynamics and Coastal Effects of Tsunamis Generated by Asteroids Impacting the Black Sea

Two-dimensional (2D) and one-dimensional (1D) shallow-water models are used to evaluate the seashore effects of the tsunami generated by an asteroid impacting the western regions of the Black Sea about 208 km from the coast. The tsunami’s speed and the effects on the coastal regions depend on many factors, among which the most important is asteroid size. The tsunami generated by a 250-m asteroid reaches the nearest land location in 24 min and needs about 2 h to arrive at all Black Sea coast. The run-up value is about 7 m high on the Turkish and Crimean coasts. In the western Black Sea regions the wave height is two or three times smaller. The run-up values strongly depend on bathymetry and topography peculiarities. The run-in value in case of the tsunami generated by a 1,000-m asteroid is up to eight times larger than in case of a 250-m impactor, depending on location. The results reported herein are upper limit values. In case of the 250-m asteroid, the real wave amplitude may be up to two times smaller. The uncertainty factor decreases in case of larger asteroids. Ways of diminishing the social consequences are briefly discussed.     

Long-term development and current status of the Barcelona continental shelf: A source-to-sink approach

The Barcelona continental shelf, off the city of Barcelona (NE Spain), is a relatively narrow canyon-bounded shelf in the northwestern Mediterranean Sea. Three medium-size rivers (Tordera, Besós and Llobregat) and several ephemeral rivulets flow into this margin. Two main domains have been recognized in the Barcelona shelf: (i) a modern, river-influenced area, and (ii) a relict, sediment depleted area, both affected by a variety of human impacts. A detailed geomorphologic study based on multibeam bathymetry and backscatter data, high resolution seismic profiles, and surface sediment samples allowed mapping and interpreting the main distinctive seafloor features on the Barcelona shelf. Modern sedimentary features reveal that the Llobregat River is the main sediment source of the Barcelona prodeltaic shelf. High-discharge fluvial events result in the formation of suspended sediment plumes and sediment waves on the shelf floor. Relict (late Pleistocene–Holocene) sedimentary features reflect that an important shift occurred in the seashore direction between MIS 4 and MIS 2, and that recent neotectonic reactivation has created a set of seafloor faults. The Barcelona inner and middle shelf is severely impacted by anthropogenic activities such as the enlargement works of the Port of Barcelona, sewage pipes, dredging, anchoring and trawling.     

Imaging and modelling the subsurface structure of volcanic calderas with high-resolution aeromagnetic data at Vulcano (Aeolian Islands,Italy)

In this paper, we present a magnetic model of the subsurface structure of Vulcano island based on high-resolution aeromagnetic data. Three profiles across the most intense magnetic anomalies over the Piano and Fossa calderas were selected for the magnetic modelling, which was constrained by structural and volcanological data, previous geophysical models, paleomagnetic data, and borehole stratigraphy obtained from two deep wells. The interpretation of the magnetic sources represents a significant contribution to the understanding of the Piano and Fossa calderas’ underlying structure, providing us with evidence of the lateral discontinuity between them at depth. We propose that the positive magnetic anomalies in the Piano caldera area are caused by: (a) the remnants of an early submarine volcano; (b) an outcropping dyke swarm related to the feeding system of the Primordial Vulcano phase (beneath Mt. Saraceno); and (c) the presence of a non-outcropping dyke system intruded along a NE–SW-oriented intra-caldera fault (beneath the eastern part of the Piano caldera). Offshore, to the west, the magnetic anomaly map suggests the presence of a submarine volcanic structure, not revealed by bathymetric data, which could represent the eruptive centre, the presence of which has been indirectly deduced from the outcrop of eastern-dipping lavas on the western seashore. Magnetic modelling of the Fossa caldera points to the presence of a highly magnetized cone-like body inside the Fossa cone, centred beneath the oldest crater rims. We interpret this body as a pile of tephritic lavas emplaced in an early phase of activity of the Fossa cone, suggesting that the volume of mafic lavas that erupted at the beginning of the construction of the Fossa edifice was more significant than has previously been deduced. Furthermore, the presence of a magnetized body inside the Fossa cone implies that high temperatures are contained in very limited spaces, do not affect its bulk inner structure, and are restricted to fumarolic conduits and vents. In addition, structures beneath the western and northern part of the Fossa caldera are revealed to have null or low magnetization, which can be ascribed to the presence of pyroclasts and hyaloclastites in this area as well as to a large volume of hydrothermally altered materials. This suggests that the hydrothermal system, with a very limited extension at present, affected a larger area in the past, especially beneath the western part of the caldera.     

Risks for poisoning of coastal and inland population due to asteroid impacts in Southern regions of Black Sea

The hydrogen sulfide rich waters of the Black Sea pose a potential danger for the surrounding land regions. The impact of an asteroid exceeding tens of meters in size may cause both a tsunami wave and a catastrophic poisonous gas release in the atmosphere. Some effects of this last phenomenon on the Southern Black Sea coastal regions are evaluated in this paper. The initial surface area of the poisonous cloud depends on asteroid size. The initial thickness of the cloud depends, in addition, on sea depth at impact location. The wind speed plays an important role in H₂S cloud dynamics. At 10 m/s wind speed, the cloud margins reach 185 km from the impact location in about 3 h. The maximum distance traveled by the hydrogen sulfide cloud increases by increasing the asteroid size and wind speed. The influence of the impact position on the distance traveled by hydrogen sulfide clouds is rather weak, as long as the seawater depth does not change significantly. The land surface area covered by the H₂S cloud generated by a 1,000 m size asteroid ranges between about 6,400 and 12,000 km². This may affect up to 3,000,000 people. When a 250 m size asteroid is considered, the covered land surface area ranges between about 1,400 and 2,100 km² and up to 120,000 people may be affected. In case of a 70 m size asteroid, the cloud covers up to 280 km² of land. This may affect up to about 70,000 people. These evaluations do not include the population of the towns on or near the seashore. A simple methodology to estimate the environmental risks of the potential asteroid impact was proposed. Sites less than 160 km from the impact place are at risk.     

卫星照片的线性破裂解译

为了研究大地震发生的地质构造背景,卫照分析是很重要的。我们解译了鄂尔多斯周围和华北地区的卫星照片。共解译出巨、大、中、小各类线性破裂4737条,发现它们的最新活动表现在:1.继承性:即新的破裂沿袭中生代以前的老断裂活动;2.新生性:部分破裂在第三纪特别是第四纪形成。两种表现在卫片影象上都相当清楚。我们认为这些由卫照识别出最新活动断裂与地震活动有一定关系。