2016年夏季南海海盆水体颗粒物粒径分布特征*     

郑文迪  周雯  曹文熙  王桂芬  邓霖  徐文龙  许占堂  李彩  蔡建南 《热带海洋学报》2018,37(5):74-85

颗粒物粒径分布(Particle Size Distribution, PSD)代表了颗粒物浓度与颗粒物粒径之间的关系, 影响着海洋生态环境和水体光学特性等。文章基于2016年夏季航次调查的生物光学剖面数据, 研究了南海海盆海域PSD的分布特征。研究发现, 幂律函数可以较好地拟合南海海盆区域的PSD, 对数空间中的实测的PSD与模拟的PSD平均决定系数高达0.95。PSD斜率(ξ)的分布范围为[1.27, 7.65], 均值为3.93±0.56。南海海盆区域表层水体的ξ均值与全球大洋表层水体的ξ均值相近, 但高于海湾等表层水体的ξ均值。ξ能较好地表征颗粒物平均粒径D_A的大小, 两者存在明显负相关关系, 即ξ值越高, D_A越小; 反之, D_A越大。通过分析T1断面的生物光学剖面数据及总体平均的PSD剖面数据, 发现PSD剖面分布特征如下: 1)表层水体的ξ值相对较高, 且D_A值相对较低, 推测可能是由于微微型藻类为主导颗粒物所致; 2) ξ值极小值层出现在次表层叶绿素浓度极大值层(Subsurface Chlorophyll Maximum Layer, SCML)中, 并伴随D_A极大值层的出现, 其原因可能是SCML中的大粒径浮游植物占比显著增加; 3)弱光层中的ξ值较SCML中的高, 但略低于表层的ξ值, 而D_A则位于表层与SCML的D_A之间, 这可能与浮游植物及其碎屑的絮凝、分解、沉降等过程相关。PSD特征影响着海水的固有光学特性, 分析发现: 由于SCML中的叶绿素浓度增加, 颗粒物散射系数(b_p(532))和颗粒物后向散射系数(b_bp(532))也相应呈现显著增加的趋势。弱光层中的平均b_p(532)与平均b_bp(532)最小。ξ与颗粒物衰减光谱斜率之间呈高分散性, Boss 等(2001b)的模型适合用于粗略估算区域性的ξ分布范围及均值。  相似文献   

Review on the study of topographic effect on seismic ground motion          下载免费PDF全文

Hong Zhou 《地震科学（英文版）》2018,31(2):110-116

Topographic effect study is a very important research topic in seismology, seismic engineering,earthquake engineering, engineering earthquake construction and engineering seismology. This paper focuses on its present development status. Post-earthquake investigation has found that the existence of topography caused more serious earthquake damage. The actual seismographs also recorded the topographic amplification effect of 6 to 7 times and even more than 10 times. Numerical simulation is an important technique to study topographic effect, which complements the lack of observed records. However researches on 3-D topographic effect are not enough and need to be studied deeper. To find the main influence factors and the quantitative relationship between topography and ground motion are required very urgently. Obviously the achievements not only can be applied in the earthquake resistant design, but also can provide the quantitative pre-earthquake disaster prediction and quantitative post-earthquake disaster evaluation.  相似文献   

成武县土地利用时空变化与水系因子的关系研究          下载免费PDF全文

徐增江 《山东国土资源》2018,34(3)

成武县位于鲁西南黄河冲积平原区,水系发达,地表水资源丰富。为了分析地表水系对成武县土地利用时空变化和空间格局的影响,该文基于不同时期的遥感影像,结合实地调查和专家意见,提取区域土地利用现状图;运用DEM地表水文分析提取河流汇流累积量、水流长度、河流网络等,根据流量选取了河网。以河流为中心向两侧作缓冲区,与土地利用现状图进行空间分析,得到不同距离缓冲区内的土地利用结构。与全区域土地利用结构对比,分析不同时期在相同的缓冲区域内土地利用特征和变化,总结土地结构变化规律,结合100m,200m,300m,400m,500m,750m,1000m不同的缓冲区;通过对比各种土地利用类型在不同距离缓冲区的时空变化,从而分析水系因子对不同土地类型时空变化的影响。结果表明,不同距离缓冲区内土地利用结构不同,随着缓冲区范围的增加,耕地、建设用地、林地、园地呈现不同的变化趋势与特点,水系因子对成武县不同土地利用方式影响程度不同,水系因素对成武县土地利用空间分异有明显影响。  相似文献   

基于贝叶斯框架的各向异性页岩储层岩石物理反演技术   总被引：1，自引：0，他引：1       下载免费PDF全文

刘财  符伟  郭智奇  刘喜武  刘宇巍 《地球物理学报》2018,61(6):2589-2600

页岩岩石物理建模旨在建立页岩矿物组分、微观结构、流体填充与岩石弹性参数的关系.对四川盆地龙马溪组页岩进行岩石物理建模研究，针对页岩黏土含量高、层间微裂缝发育等特点，利用Backus平均理论描述页岩黏土矿物弹性参数，利用Chapman理论计算与水平微裂缝有关的VTI各向异性，并利用Bond变换考虑地层倾角的影响.提出以黏土矿物纵、横波速度和孔隙纵横比为拟合参数进行岩石物理反演的方法，并引入贝叶斯框架减小反演的多解性.由已知的黏土矿物纵、横波速度和孔隙纵横比作为先验信息，并以测井纵、横波速度作为约束条件建立反演的目标函数，同时利用粒子群算法进行最优化搜索.计算结果表明，基于先验约束和粒子群算法的反演方法能够较准确地反演黏土矿物的弹性参数、孔隙形态参数以及裂缝密度等参数.计算得到的黏土纵、横波速度较高，并且在一定范围内变化，这可能与龙马溪组页岩的黏土矿物组分中具有较高弹性模量的伊利石含量较高有关，同时也与黏土定向排列等微观物性特征有关.反演得到的裂缝密度与纵波各向异性参数ε呈明显的正相关，而与横波各向异性参数γ相关性较小.另外，页岩各向异性参数与黏土垂向的纵横波速度有较强的相关性.  相似文献   

近距离上层隧道施工对下层隧道的扰动影响          下载免费PDF全文

唐强森  刘涛 《地震工程学报》2018,40(3):591-596,603

针对近距离上层隧道施工时给下层隧道稳定性造成扰动影响的现状,基于简支土体梁力学模型,研究下层隧道顶部在周期性扰动力作用下的系统振动特性,得到顶部垂直位移的动态响应数学表达式,为定量掌握最大位移峰值的大小与出现时刻提供理论依据,指出考虑振动因素时上下层隧道安全距离的确定方法。结合具体算例探索扰动力等因素对最大位移的作用规律,结果表明:扰动力振幅和隧道跨度分别增加1倍和2倍时,最大位移峰值相应增大1倍和23.9倍;隧道层间垂距和土体弹性模量分别增加2倍和3倍时,最大位移峰值相应减小88.2%和70%。当主要影响因素变化时,最大位移的波动大周期延长、波动震荡性加剧,特别是峰值处的震荡幅值增大,隧道顶部稳定性受到明显影响。  相似文献   

华南陆缘高热流区的壳幔温度结构与动力学背景          下载免费PDF全文

张健  王蓓羽  唐显春  董淼  艾依飞 《地球物理学报》2018,61(10):3917-3932

华南陆缘是我国重要的矿产、地热资源区.晚中生代以来，在太平洋板块西向俯冲，地幔热对流活动共同作用下，该区出现多期岩浆-热事件和大规模爆发式成矿作用.在前人研究基础上，本文利用地表热流观测资料、地震剪切波资料、重力位球谐系数，计算了壳-幔温度结构，分析了动力学背景.计算结果表明：华南陆缘东南沿海地带，地壳10 km以浅温度达200℃以上，居里点温度475℃，莫霍面平均温度550℃.地壳浅层较热，花岗岩中放射性元素衰变放热是地壳浅层地下水热活动的重要热源，但地壳总体温度不高，为"冷壳热幔"型热结构.地幔中，90 km深度，温度950~1250℃；120 km深度，温度1050~1400℃；150 km深度，温度1200~1450℃；220 km深度，温度1500~1700℃."热"岩石圈底界深度在110~150 km之间，西深东浅.岩石圈内，地幔应力场为挤压-伸展相间格局；岩石圈之下，地幔应力场为一个以南昌为中心、长轴NE-SW向的椭圆.分析认为，晚中生代以来，太平洋板块的西向俯冲，导致华南陆缘在区域性SE向地幔对流背景上叠加局域性不稳定热扰动，在175~85Ma期间，上地幔物质向上流动，形成不同的岩浆活动高峰期.同时，岩石圈地幔受俯冲洋壳流体的影响，含水量高，黏度小，在地幔流切向应力场作用下，岩石圈底界由西向东"波浪"状减薄.现今岩石圈之下仍具备地幔小尺度热对流温度条件，但除地表浅层外，地壳整体温度不高，岩石圈构造稳定.  相似文献   

3D P-WAVE VELOCITY STRUCTURE AT THE NORTHEASTERN MARGIN OF ORDOS BLOCK     

HAN Xiao-ming  Liu Fang  ZHANG Fan  CHEN Li-feng  LI Juan  LI Shuan-hu  YANG Hong-ying 《地震地质》2018,40(1):215-231

Using the 7 100 absolute first arrivals of P waves and 91 513 relative P arrival times of 726 events at the northeastern margin of the Ordos block since 2009, the 3D fine structure of P wave velocity within the depth of 15km in the crust was inverted by the double difference seismic tomography method. The results show that there exist obvious high-speed continuous bodies in the northwest of the study area, and their lateral areas increase gradually with depth, while the velocity of east and south is relatively low. The velocity inhomogeneity exists and differs at different depths. The lateral differences of velocity are related to seismicity and faults. The 5~15km depth profile shows that earthquakes tend to occur in the area with relatively high velocity or high speed transition zones, which to some extent reflects the fragility of regional crustal media and the strong differential movement of faults in vertical and horizontal directions where the crust body is easy to absorb and store strain energy and generate major earthquakes. A "Y"-shape low-velocity channel is present in the lower crust around Liangcheng, corresponding to the NW-trending Heilaoyao-Shahukou fault set, which may reveal the migration path of the Late Tertiary-Quaternary basalt eruption. The Helingeer M6.2 earthquake in 1976 was related to the formation of the locking section of the thermal welding in this area. The three-dimensional fine structure of P wave velocity presented in this paper provides intuitive seismological evidence for physical and chemical properties of crustal media and the deep tectonic environment of earthquake preparation.  相似文献   

RESEARCH ON PASSIVE SERVO SEISMIC ROTATIONAL ACCELERATION SENSOR WITH LARGE DAMPING     

QU Ming-zhe  GAO Feng  YANG Xue-shan  YANG Dong-xia 《地震地质》2018,40(5):1170-1178

Many strong motion records show that under the strong seismic vibration of, the torsional disfigurement of building structures is a common and serious damage. At present, there are no special sensors for measuring seismic rotation in the world. Most of the experts obtain rotational components through observing deformation, theoretical analysis and calculation. The theory of elastic wave and source dynamics also prove the conclusion that the surface of the earth will rotate when an earthquake occurs. Based on a large number of investigations and experiments, a rotational acceleration sensor was developed for the observation of the rotational component of strong ground motions. This acceleration sensor is a double-pendulum passive servo large-damped seismic rotational acceleration sensor with the moving coil transducer. When an earthquake occurs, the seismic rotational acceleration acts on the bottom plate at the same time. The magnetic circuit system and the middle shaft fixedly connected to the bottom plate follow the bottom plate synchronous vibration, and the moving part composed of the mass ring, the swing frame and the moving ring produces relative corners to the central axis. The two working coils mounted on the two pendulums produce the same relative motion with respect to the magnetic gaps of the two magnetic circuits. Both working coils at this time generate an induced electromotive force by cutting magnetic lines of force in the respective magnetic gaps. The generated electromotive forces are respectively input to respective passive servo large damper dynamic ring transducer circuits and angular acceleration adjusting circuits, and the signals are simultaneously input to the synthesizing circuit after conditioning. Finally, the composite circuit outputs a voltage signal proportional to the seismic rotational acceleration to form a seismic rotational acceleration sensor. The paper presents the basic principles of the rotational acceleration sensor, including its mechanical structure diagram, circuit schematic diagram and mathematical models. The differential equation of motion and its circuit equation are derived to obtain the expressions of the main technical specifications, such as the damping ratio and sensitivity. The calculation shows that when the damping ratio is much larger than 1, the output voltage of the passive servo large damping dynamic coil transducer circuit is proportional to the ground rotation acceleration, and the frequency characteristic of bandpass is wider when the damping ratio is larger. Based on the calibration test, the dynamic range is greater than or equal to 100dB and the linearity error is less than 0.05%. The amplitude-frequency characteristics, the phase-frequency characteristics and their corresponding curves of the passive servo rotational acceleration sensor are acquired through the calculations. Based on the accurate measurement of the micro-vibration of the precision rotating vibration equipment, the desired result is obtained. The measured data are presented in the paper, which verify the correctness of the calculation result. The passive servo large damping rotational acceleration sensor has simple circuit design, convenient operation and high resolution, and can be widely applied to seismic acceleration measurement of earthquake or structure.  相似文献   

Intermediate to Long-term Estimation of Strong Earthquake Risk Areas in the Chinese Mainland Based on Geodesic Measurements     

Zhang Jing  Zhu Yiqing  Wu Yanqiang  Zhang Xi  Yang Guohua 《中国地震研究》2018,32(2):153-172

Based on previous research results, present-day crustal deformation and gravity fields in the Chinese mainland are analyzed using the GPS data, leveling, gravity and cross-fault deformations. We analyzed strain accumulation of the major faults, and identified locked or high strain accumulation segments. Combining the effects of large earthquakes in the study area, the long-term (decade) probability of large earthquakes in the Chinese mainland is estimated.  相似文献   

山东昌邑国家级海洋生态特别保护区生态环境现状及管护对策研究          下载免费PDF全文

隽云昌  刘国宁  张颖  张守本  李秋霞  宋秀凯  马元庆  秦华伟  张志  吴倩倩  付新华 《海洋开发与管理》2018,35(7):63-71

山东昌邑国家级海洋生态特别保护区是目前国内唯一以柽柳林生态系统为主要管理和保护对象的国家级海洋保护区。为系统、全面地了解保护区内生态环境和保护物种的变化趋势,文章对山东昌邑国家级海洋生态特别保护区生态环境现状进行了监测与评价,并根据评价结果,分析了保护区保护与管理中存在的问题。研究表明,该保护区生态环境一直处于亚健康状态,为促进保护及管护,提出了加强保护区生态建设,改变保护区开发利用模式;加强能力建设,实现保护区动态监控;协调发展与保护的关系,实现资源可持续利用;大力开展柽柳生态修复,恢复柽柳的资源状况的对策建议。  相似文献