广西北流—广东化州MS 5.2级地震发震构造探讨

2019年10月12日广西北流与广东化州交界发生5.2级地震,地震发生前2 s,其北西侧发生4.2级前震。根据地震周边47个台站记录到的P波及S波震相走时数据,利用双差地震定位方法获取了104个地震的精定位结果 ,结合4.2级前震的震源机制解及5.2级主震的"中心震源机制解"进行研究探讨,综合分析认为NW-SE向米场—石窝断裂可能是北流4.2级前震和5.2级主震的主要发震构造,前震孕震过程有NEESWW向茶山断裂的参与。而5.2级主震位于米场—石窝断裂与NE-SW向信宜—廉江断裂交汇处,该交汇处应力薄弱且距离前震仅1km左右,推测4.2级前震的发生可能对5.2级地震具有触发作用,5.2级地震发生后余震主要沿米场—石窝断裂的延伸线分布。     

Low-rank seismic denoising with optimal rank selection for hankel matrices

Based on the fact that the Hankel matrix representing clean seismic data is low rank, low-rank approximation methods have been widely utilized for removing noise from seismic data. A common strategy for real seismic data is to perform the low-rank approximations for small local windows where the events can be approximately viewed as linear. This raises a fundamental question of selecting an optimal rank that best captures the number of events for each local window. Gavish and Donoho proposed a method to select the rank when the noise is independent and identically distributed. Gaussian matrix by analysing the statistical performance of the singular values of the Gaussian matrices. However, such statistical performance is not available for noisy Hankel matrices. In this paper, we adopt the same strategy and propose a rule that computes the number of singular values exceed the median singular value by a multiplicative factor. We suggest a multiplicative factor of 3 based on simulations which mimic the theories underlying Gavish and Donoho in the independent and identically distributed Gaussian setting. The proposed optimal rank selection rule can be incorporated into the classical low-rank approximation method and many other recently developed methods such as those by shrinking the singular values. The low-rank approximation methods with optimally selected rank rule can automatically suppress most of the noise while preserving the main features of the seismic data in each window. Experiments on both synthetic and field seismic data demonstrate the superior performance of the proposed rank selection rule for seismic data denoising.     

城市化背景下年最大日径流演变及影响因素研究——以长江下游秦淮河流域为例

随着气候变化和人类活动的加剧,城市化地区水文过程受到较大影响,极端水文事件发生频率显著加大,探究城市化地区洪水演变和驱动机理对于防洪减灾具有重大意义。本文以长江下游快速城市化地区的秦淮河流域为例,分析了1987—2018年期间该流域年最大日径流的演变特征,构建多元线性回归模型和广义可加GAMLSS模型识别了关键驱动因子并量化其贡献作用。结果表明:(1)城市化背景下秦淮河流域年最大日径流呈现显著上升趋势,平均增长速率为14.77 m³/(s·a),并于2001年发生显著突变。(2)汛期降水量和不透水面率是年最大日径流变化的关键驱动因素,最优模型显示前者贡献率超过了70%,表明了降水改变的决定性作用,而不透水面率贡献率超过20%则表明了下垫面的改变对年最大日径流演变存在显著影响。(3)不透水面的增加对年最大日径流和汛期降水量响应关系的影响程度从突变前的6.7%增加到突变后的10.4%,快速城市化已显著改变了流域降水-径流响应过程。研究表明,随着城市发展秦淮河流域的年最大日径流受到人类活动显著影响,洪涝威胁日趋增大,研究结果可为城市化地区防洪减灾提供一定参考。     

Toxic effects of several phthalate esters on the embryos and larvae of abalone Haliotis diversicolor supertexta

As the most widely used plasticizers in the world, phthalate esters (PAEs) are potential endocrine disruption compounds (EDCs). In the present study, the toxicity of dimethyl phthalate (DMP),diethyl phthalate (DEP), dibutyl phthalate (DBP), di (2-ethylhexyl) phthalate (DEHP) on embryogenesis and larvae development of the marine univalve Haliotis diversicolor supertexta was examined in laboratory. The results show that the malformation of embryos appeared during the experiment, such as embryos died or lysed, small transparent flocculent rings studded on the periphery of the embryo, and the larvae could failed to hatch. In embryo toxic test, embryos incubated at the highest concentration of DMP,DEP and DBP solutions showed significantly high abnormal rate compared with the control, while DEHP solutions displayed no significant difference. In larval toxic test, in all concentrations of DMP, DEP and DBP solutions, larval settlement rates were low significantly than that of the control. Similarly, DEHP solutions show nearly no effect on the larval settlement. The order of toxicity on embryos and larvae is DBP>DEP>DMP>DEHP. Being a simple and easy stimulation to indoor spawn, sensitive to environmental factors, and short culture time, the embryos of 1-1. diversicolor supertexta can be used to indicate toxicity of the PAEs.     

Study on the double-logarithmic profile of tidal flow velocity in the near-bed layers

Tidal current velocity profile in the near-bed layers has been widely studied. The results showed that velocity profile in the near-bed layer obviously departure from the traditional logarithmic profile, due to the acceleration or deceleration. Although the logarithmic linear profile can reduce the rate of deviation from this, only it is a lower-order approximate solution. In this paper, considering the unsteady and non-linear features of tidal motion, the double logarithmic profile near-bed layers in estuarine and coastal waters is established on the assumption that the turbulent shear stress along the water depth was parabolic distribution, and on the basis of Prandtl''s mixing length theory and von Karman''s self-similar theory. Having been verified the data observed at the West Solent in the south of England, and comparison of the logarithmic linear profile, it found that the double logarithmic profile is more precious than the latter. At last, the discussed results showed that:(1) The parabolic distribution of the tidal shear stresses verified good by the field data and experimental data, can be better reflected the basic features of the tidal shear stress deviating from linear distribution that is downward when to accelerate, upward when to decelerate. (2) The traditional logarithmic velocity profile is the zero-order approximation solution of the double logarithmic profile, the logarithmic linear profile is the first order, and the logarithmic parabolic profile is the second order. (3) Ignoring the conditions of diffusion and convection in the tidal movement, the double logarithmic profile can reflect the tidal properties of acceleration or deceleration, so that the calculation of the friction velocity and roughness length are more reasonable. When the acceleration or the deceleration is about zero, the double logarithmic profile becomes the logarithmic profile.     

The hydrogen peroxide impact on larval settlement and metamorphosis of abalone Haliotis diversicolor supertexta

Abalone Haliotis diversicolor supertexta is an important economic mollusk.The settlement and metamorphosis are two critical stages during its development period,which has direct influence on abalone survival and production.The influence of reactive oxygen species(hydrogen peroxide) on abalone embryo and juvenile development were examined in this study.Larvae of Haliotis diversicolor supertexta were induced to settlement and metamorphose by exposure to seawater supplemented with hydrogen peroxide.They had the best performance at 800 μmol/L.The concentration of 1 000 μmol/L or higher was toxic to the larvae,as the larvae could settle down only at benthic diatom plates without complete metamorphosis.In addition,H2O2 adding time was critical to the larval performance.24h after two-day post-fertilization was proved to be the optimal adding time.In this paper,two action mechanisms of hydrogen peroxide are discussed:(1) hydrogen peroxide has direct toxicity to ciliated cells,thus cause apoptosis;(2) hydrogen peroxide,as a product from catecholamines' autoxidation process in vivo,can reverse this process to produce neuro-transmitters to induce abalone metamorphosis.     

海城河河岸带植物群落特征及其物种多样性研究

以野外样方调查数据为基础,详细调查了海城河河岸带植物群落的组成,种类和外貌,应用重要值计算了海城河河岸带植物丰富度指数、多样性指数、均匀度指数、优势度指数,并分析了其物种的多样性差异,从而为海城河河岸带的生态修复提供理论和技术依据。结果表明:海城河河岸带植物群落20个样方中共有23科60属80种,物种组成以菊科、禾本科、蓼科、莎草科、蔷薇科植物为主,植物种类以芦苇、朝鲜碱茅、中华结缕草、金盏银盘、抱茎苦荬菜、黄花蒿、灯心草、反枝苋、狗尾草等为主。海城河河岸带植物群落结构简单,物种组成较少。群落物种多样性水平较低,从多样性指数的数量特征来看,丰富度指数的变化范围为4.00～16.00,Pielou均匀度指数的变化范围为0.52～0.93,Simpson多样性指数的变化范围为0.45～0.84,Shannon-Wiener多样性指数的变化范围为0.87～2.18,Simpson优势度指数的变化范围为0.17～0.55。海城河河岸带受到人为活动干扰,如农业生产、挖沙等人为活动干扰降低了群落多样性水平。     

一次西风槽过程过冷云水分布特征观测研究

过冷云水生消演变规律是云物理学和人工影响天气的重要研究领域。根据Hobbs 1974年提出的假定,利用飞机、卫星、雷达和雨量计等观测资料,对2012年9月21日河北一次西风槽天气过程进行观测研究,分析其过冷云水分布特征及演变规律。结果表明,槽前云系过冷水区宽厚并且过冷水含量较高,云滴浓度和均立方根直径较大并且均匀,冷云区厚而且没有分层,没有暖云配合;近槽云系中冷云区小粒子浓度降低但云滴直径增大,冷云区夹有干层,云系变厚出现暖云配合,冷暖云液态水含量较高,冷暖云区大粒子和降水粒子浓度和尺度增大,中尺度云团移动较快;槽后云系中云滴浓度最大,但云滴均立方根直径明显减小,过冷水区出现的高度下降、厚度很薄、过冷水含量较低,冷、暖云之间有干层,暖云对应的大粒子浓度和降水粒子浓度非常大,地面降水主要由暖云过程产生;云水(过冷水)含量峰值常出现在云内逆温层的上方;利用云粒子测量系统(PMS)资料分析过冷云水生消演变特征与卫星和雷达资料具有较高的一致性。     

一种新的全站仪简码测图法

提出了一种新的全站仪简码测图法,实现了多人立棱镜简码测图,提高了简码测图的野外作业效率,通过野外测图实践,证实了此方法的快速、高效。     

Crustal and Upper-Mantle Seismic Reflectors beneath the Three Gorges Reservoir Region

Seismic studies of the crustal structure beneath the Three Gorges Reservoir(TGR) region in Central China have been limited by the sparse and uneven distribution of seismic stations.To in-crease the station coverage,we made three deployments of a mobile seismologic array in the TGR re-gion during the three summers from 2008 to 2010.Here we present interpretations along a west-east profile through the central TGR region based on new seismic waveform data and a velocity model con-strained by regional earthquak...