东北地震区b值和地震年平均发生率的统计分析   总被引：5，自引：0，他引：5  

吴兆营  薄景山  刘志平  邵喜彬  李忠伟 《东北地震研究》2005,21(3):27-32,72

震级和频度关系式中的b值和地震年平均发生率是表征一个地区地震活动性的重要参数，也是地震危险性概率分析中不可缺少的计算参数。本文根据当前的地震目录，利用数理统计的方法给出了东北地震区的b值和地震的年平均发生率。该研究成果对在本区开展地震安全性评价和地震预报具有重要的参考价值。  相似文献   

Palaeoenvironmental and diagenetic reconstruction of a closed‐lacustrine carbonate system – the challenging marginal setting of the Miocene Ries Crater Lake (Germany)     

《Sedimentology》2018,65(1):235-262

Chemostratigraphic studies on lacustrine sedimentary sequences provide essential insights on past cyclic climatic events, on their repetition and prediction through time. Diagenetic overprint of primary features often hinders the use of such studies for palaeoenvironmental reconstruction. Here the potential of integrated geochemical and petrographic methods is evaluated to record freshwater to saline oscillations within the ancient marginal lacustrine carbonates of the Miocene Ries Crater Lake (Germany). This area is critical because it represents the transition from shoreline to proximal domains of a hydrologically closed system, affected by recurrent emergent events, representing the boundaries of successive sedimentary cycles. Chemostratigraphy targets shifts related to subaerial exposure and/or climatic fluctuations. Methods combine facies changes with δ ¹³C–δ ¹⁸O chemostratigraphy from matrix carbonates across five closely spaced, temporally equivalent stratigraphic sections. Isotope composition of ostracod shells, gastropods and cements is provided for comparison. Cathodoluminescence and back‐scatter electron microscopy were performed to discriminate primary (syn‐)depositional, from secondary diagenetic features. Meteoric diagenesis is expressed by substantial early dissolution and dark blue luminescent sparry cements carrying negative δ ¹³C and δ ¹⁸O. Sedimentary cycles are not correlated by isotope chemostratigraphy. Both matrix δ ¹³C and δ ¹⁸O range from ca −7·5 to +4·0‰ and show clear positive covariance (R  = 0·97) whose nature differs from that of previous basin‐oriented studies on the lake: negative values are here unconnected to original freshwater lacustrine conditions but reflect extensive meteoric diagenesis, while positive values probably represent primary saline lake water chemistry. Noisy geochemical curves relate to heterogeneities in (primary) porosity, resulting in selective carbonate diagenesis. This study exemplifies that ancient lacustrine carbonates, despite extensive meteoric weathering, are able to retain key information for both palaeoenvironmental reconstruction and the understanding of diagenetic processes in relation to those primary conditions. Also, it emphasizes the limitation of chemostratigraphy in fossil carbonates, and specifically in settings that are sensitive for the preservation of primary environmental signals, such as lake margins prone to meteoric diagenesis.  相似文献   

胶东半岛小震丛集特征研究     

李小晗  郑建常 《大地测量与地球动力学》2022,42(1):77-81

以最邻近事件距离算法为基础,结合混合概率密度分布对胶东半岛地区的小震丛集特征进行分析。结果表明：1）该地区存在明显的地震成丛现象,且近年来丛集率显著提高;2）乳山震群和莱州地震前,半岛地区均存在b值降低和丛集率升高的现象。分析认为,低b值异常配合高丛集率可能是该区域地震活动较好的预测指标。  相似文献   

风向随高度的偏转及其对指数廓线的影响——以广州主城区为例     

孙武  乔志强  李华聪 《地理研究》2022,41(8):2295-2310

在廓线指数的确定中,不同高度来流方向相同的假定很难得以保证。特别是超高层建筑密集的区域,热力与动力作用使风向随高度的变化复杂化。因此,风向的偏转产生的效应必须要给予重视。以高层建筑密集的广州主城区为例,基于激光雷达在4个不同测点获取1 km以下的垂直风塔数据,利用分钟尺度的高频样本,在划分随高度风向组合类型的基础上,分析了风向偏转对廓线指数的影响以及廓线指数α形成的机理。风向偏转的校正对指数廓线的发育在结构、均值以及高度分布上均产生影响,但最明显的优势是提高了廓线指数表达的科学性。测点所处的风场环境和来流经过的下垫面的建筑高度离散度决定了风廓线指数α。  相似文献   

A new identification method for five species of oysters in genus Crassostrea from China based on high-resolution melting analysis   总被引：2，自引：0，他引：2  

王家丰  许飞  李莉  张国范 《中国海洋湖沼学报》2014,32(2):419-425

The high phenotypic plasticity in the shell of oysters presents a challenge during taxonomic and phylogenetie studies of these economically important bivalves. However, because DNA can exhibit marked differences among morphologically similar species, DNA barcoding offers a potential means for oyster identification. We analyzed the complete sequences of the cytochrome oxidase subunit I （COI） of five common Crassostrea species in China （including Hong Kong oyster C. hongkongensis, Jinjiang oyster C. ariakensis, Portuguese oyster C. angulata, Kumamoto oyster C. sikamea, and Pacific oyster C. gigas） and screened for distinct fragments. Using these distinct fragments on a high-resolution melting analysis platform, we developed an identification method that does not rely on species-specific PCR or fragment length polymorphism and is efficient, reliable, and easy to visualize. Using a single pair of primers （Oyster- COI-1）, we were able to successfully distinguish among the five oyster species. This new method provides a simple and powerful tool for the identification of oyster species.  相似文献   

Zooplankton community analysis in the Changjiang River estuary by single-gene-targeted metagenomics     

程方平  王敏晓  李超伦  孙松 《中国海洋湖沼学报》2014,32(4):858-870

DNA barcoding provides accurate identification of zooplankton species through all life stages. Single-gene-targeted metagenomic analysis based on DNA barcode databases can facilitate longterm monitoring of zooplankton communities. With the help of the available zooplankton databases, the zooplankton community of the Changjiang (Yangtze) River estuary was studied using a single-gene-targeted metagenomic method to estimate the species richness of this community. A total of 856 mitochondrial cytochrome oxidase subunit 1 (cox1) gene sequences were determined. The environmental barcodes were clustered into 70 molecular operational taxonomic units (MOTUs). Forty-two MOTUs matched barcoded marine organisms with more than 90% similarity and were assigned to either the species (similarity>96%) or genus level (similarity<96%). Sibling species could also be distinguished. Many species that were overlooked by morphological methods were identified by molecular methods, especially gelatinous zooplankton and merozooplankton that were likely sampled at different life history phases. Zooplankton community structures differed significantly among all of the samples. The MOTU spatial distributions were influenced by the ecological habits of the corresponding species. In conclusion, single-gene-targeted metagenomic analysis is a useful tool for zooplankton studies, with which specimens from all life history stages can be identified quickly and effectively with a comprehensive database.  相似文献   

Production and Certification of a Unique Set of Isotope and Delta Reference Materials for Boron Isotope Determination in Geochemical,Environmental and Industrial Materials     

Jochen Vogl  Martin Rosner 《Geostandards and Geoanalytical Research》2012,36(2):161-175

Isotopic reference materials are essential to enable reliable and comparable isotope data. In the case of boron only a very limited number of such materials is available, thus preventing adequate quality control of measurement results and validation of analytical procedures. To address this situation a unique set of two boron isotope reference materials (ERM‐AE102a and ‐AE104a) and three offset δ¹¹B reference materials (ERM‐AE120, ‐AE121 and ‐AE122) were produced and certified. The present article describes the production and certification procedure in detail. The isotopic composition of all the materials was adjusted by mixing boron parent solutions enriched in ¹⁰B or ¹¹B with a boron parent solution having a natural isotopic composition under full gravimetric control. All parent solutions were analysed for their boron concentration as well as their boron isotopic composition by thermal ionisation mass spectrometry (TIMS) using isotope dilution as the calibration technique. For all five reference materials the isotopic composition obtained on the basis of the gravimetric data agreed very well with the isotopic composition obtained from different TIMS techniques. Stability and homogeneity studies that were performed showed no significant influence on the isotopic composition or on the related uncertainties. The three reference materials ERM‐AE120, ERM‐AE121 and ERM‐AE122 are the first reference materials with natural δ¹¹B values not equal to 0‰. The certified δ¹¹B values are ?20.2‰ for ERM‐AE120, 19.9‰ for ERM‐AE121 and 39.7‰ for ERM‐AE122, each with an expanded uncertainty (k = 2) of 0.6‰. These materials were produced to cover about three‐quarters of the known natural boron isotope variation. The ¹⁰B enriched isotope reference materials ERM‐AE102a and ERM‐AE104a were produced for industrial applications utilising ¹⁰B for neutron shielding purposes. The certified ¹⁰B isotope abundances are 0.29995 for ERM‐AE102a and 0.31488 for ERM‐AE104a with expanded uncertainties (k = 2) of 0.00027 and 0.00028, respectively. Together with the formerly certified ERM‐AE101 and ERM‐AE103 a unique set of four isotope reference materials and three offset δ¹¹B reference materials for boron isotope determination are now available from European Reference Materials.  相似文献   

Research Status and Advance in Carbon Isotope (δ13C) Variation from Stalagmite     

Huang Wei  Liu Dianbing  Wang Luyao  Zhang Zhenqiu 《地球科学进展》2016,31(9):968-983

The application of carbon isotope (δ¹³C) collected from stalagmite to reconstruct the past climate and/or ecologic evolution, relative to other preserved indicators, is much limited due to its complex influencing factors including climate outside cave and complicated and site-specific karstic process. In terms of various climate and non-climate limiting factors on stalagmite δ¹³C, and combined with a large number of geological records and modern cave monitoring data of the latest researches, the pathway and behavior of the signal transmission of δ¹³C in the cave system were analyzed. The possible relationship between δ¹³C excursions and climate oscillations under different time scales was thus discussed. Although the degree of noise becomes increasing mixed with δ¹³C on centennial scales or shorter, the climatic elements, such as temperature and humidity (or precipitation), as predominant modulators exert directly or indirectly influence on vegetation overlying the soil and associated soil CO₂ productivity on millennial-orbital scales. Future work should be focused on further deeply extracting the common δ¹³C signals from specific caves by exploring the controlling factors, both including climatic and non-climatic ones, attaching importance to the seasonal characteristics of stalagmite δ¹³C, and taking full advantage of its potential in the indication of local environmental events. The use of multi-proxy and multi-method will contribute to better understanding the interesting linkages among the δ¹³C characteristics, karstic process, global carbon cycle and associated climate change.  相似文献   

Elemental abundance analyses with DAO spectrograms: XXXIII. β UMa (A0mA1 IV‐V), α Dra (A0 III), π Dra (A2 IIIs), and κ Cep (B9 III)     

S.J. Adelman  K. Yu  A.F. Gulliver 《Astronomische Nachrichten》2011,332(2):153-158

This paper presents extended analyses of β UMa (A0mA1 IV‐V), α Dra (A0 III), π Dra (A2 IIIs), and κ Cep (B9 III) which have previously been studied in this series. α Dra is a metal‐poor star while κ Cep has solar abundances. Both β UMa and π Dra are Am stars. Whenever possible, more accurate and precise gf values replace older values. High S/N (200+) and high dispersion Dominion Astrophysical Observatory spectrograms to the red of previously obtained spectra supplement the observations. The derived rotational velocities are 45, 25, 26, and 23 km s^–1, respectively. These LTE fine analyses use the ATLAS9 and the WIDTH9 programs of R. L. Kurucz. The results of the extended and the previous analyses are in good agreement. Thus in the past decade a significant improvement in the system of gf values has not been achieved although for many lines there have been changes. The use of additional regions has increased the quality of some results (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

First detection of a magnetic field in the fast rotating runaway Oe star ζ Ophiuchi     

S. Hubrig  L.M. Oskinova  M. Schller 《Astronomische Nachrichten》2011,332(2):147-152

The star ζ Ophiuchi is one of the brightest massive stars in the northern hemisphere and was intensively studied in various wavelength domains. The currently available observational material suggests that certain observed phenomena are related to the presence of a magnetic field. We acquired spectropolarimetric observations of ζ Oph with FORS 1 mounted on the 8‐m Kueyen telescope of the VLT to investigate if a magnetic field is indeed present in this star. Using all available absorption lines, we detect a mean longitudinal magnetic field 〈B_z〉_all = 141 ± 45 G, confirming the magnetic nature of this star. We review the X‐ray properties of ζ Oph with the aim to understand whether the X‐ray emission of ζ Oph is dominated by magnetic or by wind instability processes (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献