Study on terrestiral noise in data of geomagnetic total field in North China

The terrestrial noise in the differencial data of geomagnetic total field recorded at 21h in North China was fitted by using the geomagnetic vector data from Beijing Observatory. The terrestrial noise level and its spatial feature in this region was discussed. A method, which may be useful for justifying the quality of fitting, was provided in this paper. The analysis indicates that the terrestrial noise is one of the important noise in tectonomagnetic study. It is shown that the susceptibility effect is quite small and the orientation effect is the main component in the terrestrial noise in North China. The rough spatial feature of the magnetic anomaly in crustal substance was infered from the spatial feature of terrestrial noise. The measurement precision and the source noise level of data at 21h in this region were obtained in the analysis of residual noise. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 441–447, 1993.     

浅谈我国的地质灾害风险评估

针对我国地质灾害风险评估研究现状,着重讨论了对我国地质灾害风险评估的理解,提出了中国地质灾害风险评估为灾害体易发性、承灾体的易损性、这两者耦合关系评估的结构组成及结构公式,并根据其研究对象、内容、目的等方面情况提出了地质灾害风险评估的完整概念。     

一株大口黑鲈源ST-873型肺炎克雷伯菌(Klebsiella pneumoniae)的分离鉴定及生物学特性研究

从患腹水病大口黑鲈(Micropterus salmoides)的头肾、脾脏、肝脏组织中分离到一株优势菌,生长出圆形、边缘整齐的灰白色黏液状菌落;染色镜检可见短粗、卵圆形、有荚膜的革兰氏阴性杆菌。结合形态、生理生化特征、16S rRNA基因序列分析鉴定为肺炎克雷伯菌(Klebsiella pneumoniae),MLST分析进一步确定其为ST-873型,与ST-65型聚为一支;该菌株携带aere、alls、wca和ybt四种毒力基因,具有溶血活性;人工感染大口黑鲈,发现患病鱼呈现腹水等与自然发病类似的症状,且病鱼内脏的分离菌株与攻毒菌株相同;经统计,其LD50为3.4×10⁷ CFU/mL,具有中等生物被膜形成能力。耐药性分析结果显示,该菌株携带bla-shv、sul2、aadA和tetB四种耐药基因,对β-内酰胺类、氨基糖苷类、喹诺酮类、黏菌素类药物敏感,对四环素类、磺胺类、林可酰胺类、利福霉素类耐药;中药三七、款冬花对分离菌株有明显抑制作用。研究探明了大口黑鲈腹水病的主要病原,可为鱼源肺炎克雷伯菌的诊断和防治提供科学依据和数据参考。     

Magnetic Susceptibility and Heavy Metals Distribution from Risk‐cultivated Soil around the Iron–Steel Plant,China

Magnetic susceptibility is a non‐conventional way that can be used for evaluating proxy soil heavy metals pollution. The paper monitors available heavy metals (Cu, Fe, Zn, and Mn) present in cultivated soils around iron–steel plant by soil magnetic susceptibility. Our study was located in an area with high pollution with small grid density of 250 m in China. Results showed that low field magnetic susceptibility was significantly correlated with available Cu, Zn, and Mn. No clear association exists between magnetic susceptibility and available Fe, soil organic matter, pH. Frequency dependent susceptibility >5% suggests the possible presence of super‐paramagnetic particles, fly ashes produced during coal combustion.     

Quantitative measurements on the paleo-weathering intensity of the loess-soil sequences and implication on paleomonsoon

The loess-soil sequences in northern China provide a near continuous record of Quaternary paleoclimate. The pedogenetic intensity of the sequences is closely linked with the variations of the East Asian summer monsoon. In this study, 2181 samples from the Changwu and Xifeng loess sections are analyzed and two high-resolution paleo-weathering timeseries of the last 1.2 Ma are generated, using the ratio of CBD extractable free Fe₂O₃ (FeD) versus the total iron (FeT). This new index is compared with micromorphological features, low-frequency magnetic susceptibility, frequency-dependent magnetic susceptibility, and the Rb/Sr ratio^[5,6]. The results suggest that the FeD/FeT ratio is able to better reflect the degree of soil development. Since the chemical weathering of loess in the Loess Plateau region mainly depends upon the summer precipitation and temperature under modern climate condition, which are closely associated with strength of summer monsoon, and the chemical weathering intensity of loess primarily reflects the variations of the summer monsoon circulation.     

Using magnetic susceptibility to find Precambrian impact ejecta: A proposal

Layers with high magnetic susceptibility contain heavy minerals that are the most likely to preserve signatures of impact in metamorphosed Precambrian rocks. The following impact indicators are resistant to alteration and metamorphism and are likely to be found in heavy mineral layers: impact diamond, SiC, shocked zircon, high-pressure TiO₂ phases, reidite, and high-pressure chromite. Coesite and stishovite could also be present but are not likely to be preserved in rocks metamorphosed above the greenschist facies. Looking for layers with high magnetic susceptibility will also identify layers that might contain concentrations of zircon for dating.     

藏南泽当地区大反向逆冲断层变形研究——以磁组构与EBSD组构分析为例

仁布-泽当逆冲断层是喜马拉雅大反向逆冲断层（GCT）在藏南地区的重要延伸部分,也是喜马拉雅造山带北部边界新生代最为活动的构造单元之一。新生代以来特提斯喜马拉雅的构造变形组构特征的研究对于深入理解碰撞造山带演化与高原隆升具有重要构造意义。本文综合GCT泽当-琼结段断层的宏观与微观变形特征,对断裂带石英脉、围岩中石英和云母矿物的电子背散射（EBSD）组构及断层两侧岩石磁组构（AMS）特征进行对比分析。结果表明对AMS主要贡献来自顺磁性云母、绿泥石等,磁化率各向异性椭球体以压扁状为主,磁面理与构造面理（劈理、断层面）基本重合,显示较强的构造变形磁组构特征;磁线理优选方向近南北向,且与观测北向逆冲断层方向一致,揭示剪切作用在变形过程中的持续作用。研究发现泽当地区GCT附近石英微观结构从围岩至断层区,石英至少呈现3种不同类型的微观变形机制：围岩区溶解蠕变、断裂带石英以膨凸重结晶和亚颗粒旋转重结晶作用为主。断裂带石英的c轴EBSD组构指示变形为低温（300~400℃）环境,其中黑云母的结晶学优选（CPO）与磁组构主轴优选方向存在高度的一致性,进一步证实了顺磁性矿物黑云母对AMS的主要贡献。综合研究表明泽当地区GCT的韧性变形是断层处在中上地壳韧性带的活动阶段变形的结果,也代表了特提斯喜马拉雅在碰撞、高原隆升期的变形主要特征。

     

Artificial neural network and liquefaction susceptibility assessment: a case study using the 2001 Bhuj earthquake data,Gujarat, India

This study pertains to prediction of liquefaction susceptibility of unconsolidated sediments using artificial neural network (ANN) as a prediction model. The backpropagation neural network was trained, tested, and validated with 23 datasets comprising parameters such as cyclic resistance ratio (CRR), cyclic stress ratio (CSR), liquefaction severity index (LSI), and liquefaction sensitivity index (LSeI). The network was also trained to predict the CRR values from LSI, LSeI, and CSR values. The predicted results were comparable with the field data on CRR and liquefaction severity. Thus, this study indicates the potentiality of the ANN technique in mapping the liquefaction susceptibility of the area.