渤海强对流天气监测及概念模型初建

利用micaps系统个例库、秦皇岛雷达、天津雷达、FY-2E红外云图、海岛站、GPS闪电定位仪、探空及中尺度物理量场等资料,采用同步资料叠加分析方法,对2007-2011年4-10月出现渤海西岸区至海区强对流天气的25个例进行综合分析和对应关系的研究.初步得出:(1)强对流发生时三类天气尺度背景场条件下的高空与低层急流配置及K指数和SI指数对应值,渤海边界层辐合线与强对流天气落区对应关系;(2)同步卫星云图中尺度MCC象元动态特征及TBB值;(3)海区中β尺度单体及多单体风暴雷达反射率因子、回波顶高特征及阈值,回波顶高与雷电分布对应关系;(4)初步建立渤海强对流天气概念模型,归纳海区强对流预警指标.在2012年5-6月业务试验中效益显著,为渤海海洋强对流天气监测、精细化预报方法研究提供参考依据.     

植被状态指数VCI与几种气象干旱指数的对比——以河南省为例

使用1982-2006年GIMMS AVHRR NDVI数据集与同期的CI、K、Pa、SPI、Z、PDSI等干旱指数做了对比分析, 讨论了河南省植被状态指数VCI对气象干旱的滞后效应及干旱监测能力. 结果表明: VCI指数与气象干旱指数的相关性受不同下垫面的影响较大, 农地的VCI与气象干旱指数相关性要明显高于林地, 农地VCI与气象干旱指数呈现正相关关系. 在河南省不同的作物生长阶段, VCI对气象干旱有着不同的滞后效应, 其中, 3-5月份冬小麦生长期VCI对气象条件的反应滞后1~3个月, 7、9月份夏玉米生长期VCI对气象条件的反应滞后1月. 总体上看, 结合前期的气象数据, VCI对河南省气象干旱有一定的指示作用和监测能力.     

Accumulation and exploration of gas hydrate in deep-sea sediments of northern South China Sea

The large deep-sea area from the southwestern Qiongdongnan Basin to the eastern Dongsha Islands,within the continental margin of northern South China Sea,is a frontier of natural gas hydrate exploration in China.Multiform of deep-sea sedimentations have been occurred since late Miocene,and sediment waves as a potential quality reservoir of natural gas hydrate is an most important style of them.Based on abundant available data of seismic,gravity sampling and drilling core,we analyzed the characteristics of seismic reflection and sedimentation of sediment waves and the occurrence of natural gas hydrate hosted in it,and discussed the control factors on natural gas hydrate accumulation.The former findings revealed the deep sea of the northern South China Sea have superior geological conditions on natural gas hydrate accumulation.Therefore,it will be of great significance in deep-sea natural gas hydrate exploration with the study on the relationship between deep-sea sedimentation and natural gas hydrate accumulation.     

Using 4C OBS to reveal the distribution and velocity attributes of gas hydrates at the northern continental slope of South China Sea

To investigate the distribution and velocity attributes of gas hydrates in the northern continental slope of South China Sea, Guangzhou Marine Geological Survey conducted four-component (4C) ocean-bottom seismometer (OBS) surveys. A case study is presented to show the results of acquiring and processing OBS data for detecting gas hydrates. Key processing steps such as repositioning, reorientation, PZ summation, and mirror imaging are discussed. Repositioning and reorientation find the correct location and direction of nodes. PZ summation matches P- and Z-components and sums them to separate upgoing and downgoing waves. Upgoing waves are used in conventional imaging, whereas downgoing waves are used in mirror imaging. Mirror imaging uses the energy of the receiver ghost reflection to improve the illumination of shallow structures, where gas hydrates and the associated bottom-simulating reflections (BSRs) are located. We developed a new method of velocity analysis using mirror imaging. The proposed method is based on velocity scanning and iterative prestack time migration. The final imaging results are promising. When combined with the derived velocity field, we can characterize the BSR and shallow structures; hence, we conclude that using 4C OBS can reveal the distribution and velocity attributes of gas hydrates.     

城镇防沙的理论框架与技术模式

城镇防沙是在国家需求推动下产生的新领域,在没有形成自身理论体系的情况下,只能以风沙物理学、治沙工程学、恢复生态学,以及沙漠化防治和可持续发展等相关理论与技术为基础,通过工程实践和理论研究逐步建立城镇防沙理论体系。初步总结出的城镇防沙理论体系包括风沙灾害成因与区域风沙流场特征、城镇周边土地利用空间格局优化、防沙工程体系优化配置、防沙工程效率评估与预测4个分支领域,14项主要研究内容和9个支撑学科;技术体系包括8个分支技术领域和一个总目标（即:城镇防沙技术优化模式）。除青藏高原外的城镇防沙技术模式具有圈层结构特征,第一圈层都是以市（镇）区为核心的绿化景观带。对于地处半湿润风沙区外缘的城镇,第二圈层为高效农牧业生产区,第三圈层为生态涵养圈,第四圈层为封禁保护圈。对于半湿润风沙区内部的城镇,第二圈层为农牧业生产与沙丘封禁区,第三圈层为封禁保护圈。对于半干旱风沙区城镇,第二圈层为沙丘（地）封禁与农牧业生产区,分为近郊设施农业圈、远郊沙丘（地）封禁与农牧户独立生产圈两个次级圈层,第三圈层为沙丘（地）封禁保护圈。对于干旱风沙区城镇,第二圈层为节水灌溉农业区,第三圈层为外围防护带,第四圈层为封禁保护带。对于地处青藏高原山间盆地的城镇,防沙工程一般采取近郊“防护林带+人工草地+灌溉系统”,外层为“沙障+防护林带+人工草地+灌溉系统”,再外层为“防护林带+草地改良+封禁保护”的布局模式。对于地处青藏高原河流宽谷的城镇,防沙工程技术模式在宏观上根据河道走向布局,局部充分考虑防沙治沙与河道整治、水土流失和地质灾害治理有机结合,细节上依据沙尘源地类型和分布地貌位置选择防沙技术。     

Effect of tidal stress on fault nucleation and failure of the 2007 Ms6.4 Ning’er earthquake

Based on calculations of the tidal Coulomb failure stress and investigations of the correlation between the Earth tide and the Ning’er earthquake sequence, the processes of fault nucleation and failure were simulated. In these simulations we consider the influence of tidal stresses using the rate- and state-dependent friction laws. Furthermore, the effects on tidal triggering due to the stress amplitude and periodic oscillation properties were investigated, and the triggering effects between the tidal normal and tidal shear stresses were compared. The results showed that the Ning’er earthquake sequence was a physical consequence of tidal effects. A transition period T₀ exists between the nucleation and failure processes of a seismic fault. When the period T of stress is equal to or becomes larger than T₀, the fault response becomes dependent on the periodic features of the loading stress; however, for T < T₀, the response of the fault is nearly independent of the period. Both the tidal normal and tidal shear stresses have similar effect in the nucleation and failure processes; the clock changes generally increase with the maximum amplitudes of the tidal stresses. Tidal normal and tidal shear stresses with positive amplitudes mainly induce earthquake triggering; however, the triggering effects induced by negative tidal stresses are smaller and faults are not sensitive to negative tidal stresses. Our results primarily reveal the physical mechanisms of tidal stress triggering.     

Mining knowledge from result comparison between spatial clustering themes

This paper introduces some definitions and defines a set of calculating indexes to facilitate the research, and then presents an algorithm to complete the spatial clustering result comparison between different clustering themes. The research shows that some valuable spatial correlation patterns can be further found from the clustering result comparison with multi-themes, based on traditional spatial clustering as the first step. Those patterns can tell us what relations those themes have, and thus will help us have a deeper understanding of the studied spatial entities. An example is also given to demonstrate the principle and process of the method.     

主题公园声景观优化研究——以常州中华恐龙城为例

声景观是旅游景观研究的新领域,声景观的设计思想为景观研究与开发提供了新的理念.以常州中华恐龙城为例,研究游客对主题公园声景观的舒适度感知.研究发现,游客的声舒适度受到声音客观参数和主观感知的影响,当声景观音量处于特定阈值内时,游客声舒适度体验最为满意,同时游客对能够传递主题公园文化内涵的声音元素最为敏感.在此基础上,运用正设计、负设计和零设计的方法,提出了主题公园声景观优化设计的思路.     

High-resolution seismic tomography of the upper crust in the source region of the April 20, 2013 Lushan earthquake and its seismotectonic implications

Both P- and S-wave arrivals were collected for imaging upper crustal structures in the source region of the April 20, 2013 Lushan earthquake. High-resolution, three- dimensional P and S velocity models were constructed by travel-time tomography. Moreover, more than 3700 after- shocks of the Lushan earthquake were relocated via a grid search method. The P- and S-wave velocity images of the upper crust show largely similar characters, with high and low velocity anomalies, which mark the presence of sig- nificant lateral and vertical heterogeneity at the source region of the Lushan earthquake. The characteristics of the velocity anomalies also reflect the associated surface geo- logical tectonics in this region. The distributions of high velocity anomalies of both P- and S-waves to 18 km depth are consistent with the distributions of relocated after- shocks, suggesting that most of the ruptures were localized inside the high velocity region. In contrast, low P and S velocities were found in the surrounding regions without aftershocks, especially in the region to the northeast of the Lushan earthquake. For the relocated aftershocks of the Lushan earthquake from this study, we found that mostaftershocks were concentrated in a zone of about 40 km long and 20 km wide, and were located in the hanging wall of Dayi-Mingshan fault. The focal depths of aftershocks increase from the southeast to the northwest region in the direction perpendicular to the fault strike, suggesting that the fault ruptured at an approximate dip angle of 45°. The main depths of the aftershocks in the northwest of the main shock are significantly shallower than expected, revealing the different seismogenic conditions in the source region.     

The characteristics of shear wave splitting in the source region of the April 20, 2013 Lushan earthquake

Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams, this paper preliminarily contains the polarization directions of fast shear wave and the time-delays of split shear waves at every station, and analyzes the crustal anisotropic characteristics in the source region. In the study area, the polarization direc- tions at stations BAX, TQU, L 132, L 133, L 134, and L 135 are northeast, which is consistent with the strike of Dachuan- Shuangshi fault. There are two polarization directions at MDS and L131, which are northeast and southeast. The scatter of polarization directions suggests the complex stress field around these two stations where two faults intersect. For the normalized time-delays at every station, the range is 1.02-8.64 ms/km. The largest time-delay is from L134 which is closest to the mainshock, and the smallest one is from L133. The variations in time-delays show the decreasing at stations BAX, L134, and L135 because of the stress-relaxation after earthquake.