苏门答腊--蒙古(1935～1957)地震大迁移的回顾

为了分析2004年12月26日苏门答腊Ms8．9大地震对大陆地震形势的影响,本文介绍了1935～1957年苏门答腊-蒙古地震大迁移事件,时间持续22年,长度4600km,迁移速度205km／a。迁移以1935年12月28日苏门答腊Ms7．7地震为起点,从印度-澳大利亚板块与欧亚板块南部边界俯冲事件开始,向北经安达曼海沟到达缅甸弧和喜马拉雅弧东端后,进入中国大陆,沿着中蒙大陆中轴地震带直抵蒙古。     

甘肃中川地区雷暴地闪特征的初步分析

本文分析了1987年6月28日甘肃中川地区一次雷暴过程中地面4个测站的电场资料,并定量估算了4个地闪的8个回击所中和的电荷量及其高度。负地闪回击所中和的电荷离地高度为4km左右(对应的环境温度为-11.2℃),而正地闪回击所中和的电荷离地高度为2km左右(环境温度+4.9℃)。负地闪大多发生在云闪后的电场恢复阶段,且在开始时往往具有持续几百毫秒的云内放电过程。其激发过程可能是首先在云底部正电荷区产生向上传输的持续正流光,导致云中部负电荷向下移动,并引发向下传输的负先导,最终导致地闪回击的发生。     

Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope.     

Chronology and petrogenesis of the Hejiazhuang granitoid pluton and its constraints on the Early Triassic tectonic evolution of the South Qinling Belt

The Hejiazhuang pluton is located in the South Qinling Tectonic Belt(SQTB)in the north side of the Mianxian-Lueyang Suture Zone,and consists dominantly of granodiorites.LA-ICP-MS zircon U-Pb dating and Lu-Hf isotopic analyses reveal that these granodiorites of the Hejiazhaung pluton emplaced at~248 Ma,and show a large variation in zirconεHf(t)values from4.8 to 8.8.These granodiorite samples are attributed to high-K to mid-K calc-alkaline series,and characterized by high SiO2(66.6%–70.0%),Al2O3(15.04%–16.10%)and Na2O(3.74%–4.33%)concentrations,with high Mg#(54.2–61.7).All samples have high Sr(627–751 ppm),Cr(55–373 ppm)and Ni(17.2–182 ppm),but low Y(5.42–8.41 ppm)and Yb(0.59–0.74 ppm)concentrations with high Sr/Y ratios(84.90–120.66).They also display highly fractionated REE patterns with(La/Yb)N ratios of 18.9–34.0 and positive Eu anomalies(δEu=1.10–2.22)in the chondrite-normalized REE patterns.In the primitive mantle normalized spidergrams,these samples exhibit enrichment in LILEs but depletion in Nb,Ta,P and Ti.These geochemical features indicate that the granodioritic magma of the Hejiazhuang pluton was derived from the partial melting of hybrid sources comprising the subducted oceanic slab and sediments,and the melts were polluted by the mantle wedge materials during their ascent.The emplacement ages and petrogenesis of the Hejiazhuang pluton prove that the initial subduction of the Mianlue oceanic crust occurred at~248 Ma ago,and the SQTB was still under subduction tectonic setting in the Early Triassic.     

数字形变观测的高频抖动信号对地震前兆响应分析

通过对河南荥阳地震台水管观测记录中的60例“高频抖动信号”,与周围250 km范围内地震事件在时间域的前兆响应的统计分析,结果表明,这种信号与地震事件之间具有一定程度的前兆响应关系.认为该高频抖动信号与周围地震具有内在的关联性,是地壳形变过程的一种前兆反应,具有一定的前兆意义.     

山西定襄七岩泉新旧测氡仪水氡测值稳定性及映震分析

2014年山西定襄七岩泉新增BHC-336智能定标器,对新、旧2套测氡仪的水氡测值,就稳定性、数据一致性、内在质量等进行对比分析,结果显示,因存在系统误差,2台测氡仪水氡测值稳定性均值存在差异,测量精度和性能具有一致性;与新测氡仪相比,旧测氡仪水氡测值相对偏差和均值标准误差更小,精度更高,数据相关程度较高,数据稳定性更好。定襄水氡对华北5级以上地震具有较好的映震能力,新测氡仪对2016年4月7日原平4.6级地震映震效能比旧测氡仪灵敏。     

旅游发展背景下乡村空间正义的主体博弈与协商——广州石屋新村案例

以广州石屋新村为案例地,通过深入访谈、参与式观察以及收集文本材料等方式获取素材,运用扎根理论进行编码分析,探讨旅游发展背景下乡村空间正义主体博弈与协商的维度与过程。研究发现：① 乡村空间正义主体博弈与协商的内容主要包括分配正义、居住正义、边界正义和信仰正义4个维度,贯穿4个维度的核心和焦点是权力正义。② 4个维度彼此交织,相互影响,前2个维度呼应了马克思空间正义思想的部分观点,后2个维度是中国语境下的理论创新。③ 乡村转型发展过程中杂糅了政府、企业、村民各自的诉求,导致不同主体展演了多元复杂动态的空间正义博弈与协商过程。     

流形上的空间密度聚类算法研究

研究流形上的聚类分析，针对基于密度的空间聚类引入了流形概念，提出1种基于流形的密度聚类算法，该方法将流形的概念与聚类相结合，可以适用于样本为复杂分布的聚类。文中通过实例证明此算法的有效性。     

An Accurate Method of Computing the Gradient of Seismic Wave Reflection Coefficients (SWRCs) for the Inversion of Stratum Parameters

The optimization inversion method based on derivatives is an important inversion technique in seismic data processing, where the key problem is how to compute the Jacobian matrix. The computational precision of the Jacobian matrix directly influences the success of the optimization inversion method. Currently, most of the AVO (amplitude versus offset) inversions are based on approximate expressions for the Zoeppritz equations to obtain the derivatives of the seismic wave reflection coefficients (SWRCs) with respect to the stratum parameters. As a result, the computational precision and range of applications of these AVO inversions are restricted undesirably. In order to improve the computational precision and to extend the range of applications of AVO inversions, the partial derivative equations of the Zoeppritz equations are established, with respect to the ratios of wave velocities and medium densities. By solving the partial derivative equations of the Zoeppritz equations accurately, we obtained the partial derivative of SWRCs with respect to the ratios of seismic wave velocities and medium densities. With the help of the chain rule for derivatives, the gradient of the SWRCs can be accurately computed. To better understand the behavior of the gradient of the SWRCs, we plotted the partial derivative curves of the SWRCs, analyzed the characteristics of these curves, and gained some new insight into the derivatives. Because only a linear system of equations is solved in our method without adding any new restrictions, the new computational method has both high precision and a quick running speed; it is not only suitable for small incident angles and weak reflection seismic waves but also for large incident angles and strong reflection seismic waves. With the theoretical foundations established in the article, we can further study inversion problems for layered stratum structures and we can further improve the computational speed and precision of the inversions.     

Assessment of PPP integer ambiguity resolution using GPS,GLONASS and BeiDou (IGSO,MEO) constellations

Although integer ambiguity resolution (IAR) can improve positioning accuracy considerably and shorten the convergence time of precise point positioning (PPP), it requires an initialization time of over 30 min. With the full operation of GLONASS globally and BDS in the Asia–Pacific region, it is necessary to assess the PPP–IAR performance by simultaneous fixing of GPS, GLONASS, and BDS ambiguities. This study proposed a GPS + GLONASS + BDS combined PPP–IAR strategy and processed PPP–IAR kinematically and statically using one week of data collected at 20 static stations. The undifferenced wide- and narrow-lane fractional cycle biases for GPS, GLONASS, and BDS were estimated using a regional network, and undifferenced PPP ambiguity resolution was performed to assess the contribution of multi-GNSSs. Generally, over 99% of a posteriori residuals of wide-lane ambiguities were within ±0.25 cycles for both GPS and BDS, while the value was 91.5% for GLONASS. Over 96% of narrow-lane residuals were within ±0.15 cycles for GPS, GLONASS, and BDS. For kinematic PPP with a 10-min observation time, only 16.2% of all cases could be fixed with GPS alone. However, adding GLONASS improved the percentage considerably to 75.9%, and it reached 90.0% when using GPS + GLONASS + BDS. Not all epochs could be fixed with a correct set of ambiguities; therefore, we defined the ratio of the number of epochs with correctly fixed ambiguities to the number of all fixed epochs as the correct fixing rate (CFR). Because partial ambiguity fixing was used, when more than five ambiguities were fixed correctly, we considered the epoch correctly fixed. For the small ratio criteria of 2.0, the CFR improved considerably from 51.7% for GPS alone, to 98.3% when using GPS + GLONASS + BDS combined solutions.