Fault plane parameters of Sanhe-Pinggu M8 earthquake in 1679 determined using present-day small earthquakes

The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method. Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows: the strike is 38.23°, the dip angle is 82.54°, the slip angle is -156.08°, the fault length is about 80 km, the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 km. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault, southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earthquake and seismic-wave velocity profile in the focal area all verified our study result.     

Observational evidence of the Yellow Sea warm current

The Yellow Sea Warm Current (YSWC) is one of the principal currents in the Yellow Sea in winter. Former examinations on current activity in the Yellow Sea have not observed a stable YSWC because of the positioning of current meters. To further understand the YSWC, a research cruise in the southern Yellow Sea was carried out in the winter of 2006/2007. Five moorings with bottom-mounted acoustic Doppler current profilers (ADCP) were deployed on the western side of the central trough of the Yellow Sea. The existence and distributional features of the YSWC were studied by analyzing three ADCP moorings in the path of the YSWC in conjunction with conductivity-temperature-depth (CTD) data over the observed area in the southern Yellow Sea. The results show the following. (1) The upper layer of the YSWC is strongly influenced by winter cold surge; its direction and speed often vary along a south-north axis when strong cold surges arrive from the north. (2) The YSWC near the bottom layer is a stable northwest flowing current with a speed of 4 to 10 cm/s. By combining the analyses of the CTD data, we speculate that the core of the YSWC may lie near the bottom. (3) On a monthly average timescale, the YSWC is stably oriented with northward flow from the sea surface to the sea floor.     

ESR DATING OF CORAL REEFS IN THE SOUTH CHINA SEA

ESR dating of aragonitic and calcitic corals , eolianite , calcrete , and corallineae from coral reefs in the South China Sea was applied to study of Quaternary reef geology . The ESR ages of calcitic corals correlated with the biostratigraphy , lithostratigraphy and geochemistry of Well Xi-Chen-1 and the oxygen-isotope stratigraphy of deep sea sediments, were reliable and up to 1.26 Ma. The selection of signals for dating and other related problems are discussed .     

黄河三角洲的￣（210）Pb剖面与再沉积作用

根据黄河三角洲东部钻孔岩芯的￣（２１０）Ｐｂ剖面资料，经标准化消除了因粒级不同所造成￣（２１０）Ｐｂ浓度变化的影响后，显示该孔的２１０ｐｂ剖面可分为１１段。每段呈指数衰减，段与段之间呈现￣（２１０）Ｐｂ放射性比度逆增，反映了由于再沉积作用造成￣（２１０）Ｐｂ的稀释作用。由此分析该区沉积和再沉积历史     

震源机制一致性的预测意义

我们利用层状介质点源位错模型,由区域地震台网垂直向记录的直达P、S波最大振幅资料,反演中小地震的震源机制的方法,分别得到大同震区1990～2002年的620次震源机制、张北震区1998年1月至1999年3月的145次震源机制.     

A preliminary study on the lithospheric thermal-rheological structure of the East Qinling orogenic belt

This paper considers the lithospheric rheological structure of the East Qinling orogenic belt to explore its geodynamics. The lithospheric rheological structure was calculated by the constraints of the lithospheric temperature structure. The thermal-rheological stratification structures of the lithosphere in the East Qinling orogenic belt present different features from each other within different tectonic units. The hinterland fault-bounded fold zone (HLZ) and the North Qinling thick-skinned imbricated thrust zone (NQL) in the northern half part of the Qinling orogen, with a temperature of 305°C for the Moho boundary, are characterized by “cold” geotherm, thickened lithosphere and the model C for rheological stratification structure. The South Qinling tectonic zone (SQL), with a mean temperature of 642°C and a high temperature of 826°C for the Moho boundary, has obvious features with the model H of “hot” geotherm, thinned lithosphere and intensive rheological behavior within moderate-lower crust and top of the upper mantle. During post-orogenesis, the NQL, being the convergent frontal region of continental subduction beneath the Qinling orogen by both the North China craton (NC) and Yangtze craton (YZ), is in a coexistence period of a dominantly thickened lithosphere and an initial delamination, and the SQL, probably under pluming, has been developing new delamination and underplating and partial melting within the crust in its axel area and recycling for mass and energy (in the forms of heat transfer and convection) between the crust and mantle. Translated from Journal of Northwest University (Natural Science Edition), 2005, 35(5): 601–605 [译自: 西北大学学报 (自然科学版)]     

南海北部陆缘大陆架科学钻探选址：珠江口盆地沉积源汇启示

南海海盆自1998年始开展了一系列大洋科学钻探，取得了重大成就，但揭开南海海盆打开过程的关键记录在南海北部陆缘大陆架。因此，开展南海北部陆缘科学钻探非常必要。珠一坳陷位于南海北部珠江口盆地，不仅具有巨大的油气资源潜力，而且记录了南海海盆打开前的地质背景。该地区的物源特征分析对于揭示物质源汇过程、重建盆地构造演化过程、预测优质储层具有重要指示作用，一直是当前研究的热点，也可从沉积学角度为论证南海大陆架科学钻探选址提供依据。本文采用锆石LA- ICP- MS U- Pb定年技术，结合锆石CL图像及稀土元素配分特征，对珠一坳陷东西两侧典型地区的样品锆石进行了物源示踪、沉积源汇分析，并探讨其物源变化的构造成因。结果表明，下始新统下文昌组沉积期到上始新统上文昌组- 下恩平组沉积期，坳陷物源由盆内转换为盆外供应为主。其中，恩平凹陷部分洼陷由于没有文昌组沉积地层，下恩平组仍以盆地内物源供给为主；惠州凹陷和陆丰凹陷则从上文昌组开始转为盆外物源供给。惠州和陆丰地区上始新统恩平组、渐新统珠海组、下中新统珠江组地层锆石自形程度较低，磨圆度较高，边缘破坏较为严重，年龄分布较为分散，稀土元素配分特征与基底不同，说明上文昌组- 恩平组地层沉积之后，坳陷主要接受盆外华南板块物源供给。该物源转换与~43 Ma时珠一坳陷裂陷作用自南向北的转换密切相关。     

夏季不同天气条件下风廓线雷达探测精度分析

利用2016年6—8月沈阳地区TWP8-L型风廓线雷达观测资料,判断大气的均匀性,计算风廓线雷达的探测精度,并与探空气球的观测资料进行对比分析,得到晴空和不同降水条件下的风廓线雷达探测精度随高度的变化情况。研究结果表明,1000m高度以下风廓线雷达的探测精度较高。在无降水和均匀降水条件下,风廓线雷达的水平探测范围内大气均匀稳定,东西波束和南北波束测得的径向风对称性较好,(U_W-U_E)和(V_S-V_N)的平均差和标准差值较小;与GTS1型探空仪风速精度相差小于2.9m/s,两者相关性较好,风廓线雷达探测水平风的准确性较高。在探测范围不均匀的降水条件下,大气在风廓线雷达的水平探测范围内不均匀,东西波束和南北波束测得的径向风的对称性较差,垂直速度变化差异较大;U_W-U_E和V_S-V_N平均差和标准差值较大;与GTS1型探空仪风速精度相差大于2.0m/s,两者相关性较差,风廓线雷达探测水平风的准确性较低,需要进一步改进算法,改善数据质量,提高探测性能。     

北黄海冷水团温度年际变化研究

本文基于1976—2006年国家标准断面(大连—成山头)调查资料,结合ECMWF气温、风速以及辐射等再分析资料,研究了北黄海冷水团的低温中心以及北部锋面的年际变化规律,并对其与气候年际变化信号的关系做了相关性分析以及EOF分析,研究了影响北黄海冷水团的诸多因素。研究结果表明,北黄海冷水团及其北部锋面强度存在明显的年际变化特征,北黄海冷水团中心最低温度具有升温趋势,北部锋面强度具有减弱趋势。分析发现,前冬海温,当地气温,经向风场以及辐射通量都对来年北黄海冷水团的强度存在影响,东亚冬季风的年际变异是影响北黄海冷水团温度年际变化的主要机制,El Nio、La Nia事件成熟期滞后于北黄海冷水团最低温度的相对低值、高值出现,ENSO通过与东亚冬季风的相互作用与北黄海冷水团相联系。     

联合卫星测高技术的船载声呐测深测线密度设计

针对目前船载声学海深测量技术应对大面积海域海底地形数据获取效率仍然较低的问题,提出了联合卫星测高技术的船载声呐测深测线布设技术方案;并结合目标海域重力数据复杂程度,给出了满足海底地形模型构建精度需求的测线密度布设指标.首先利用导纳函数反演方法恢复实验中16块海域海底地形;然后联合水深测量控制点,应用自适应测线密度计算方法得到各区域的最佳测线布设密度指标;最后选择目标海域7个重力异常特征参量为参考,引入主成分分析法探讨了各区域的重力数据复杂程度.实验结果表明,目标海域重力数据复杂程度与最佳船测海深测线密度存在较强的相关性.在三等海道测量精度标准下,不同复杂程度区域的测线密度存在1'～9'的较大差别,复杂区域需要布设的测线明显较密.