Spatial Correlation Anomalies of the Diurnal Variation of the Geomagnetic Vertical Component before the Yingjiang MS6.1 and Ludian MS6.5 Earthquakes

Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang M_S6.1 earthquake and the Ludian M_S6.5 earthquake in 2014. We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20, 2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations.Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang M_S6.1 earthquake and the Ludian M_S6.5 earthquake are located in the gradient zone or near the gradient zone.     

川滇地区烈度计台站测定震级校正分析

烈度计台与测震台的布设环境、仪器类型不同,所测定的震级值存在一定差异。收集2017-2019年川滇地区301个烈度计台站记录的46次M_L 3.0以上地震,进行震级校正。统计烈度计实测震级值与测震台网平均震级值的偏差,对原量规函数进行修正,进而做台站校正。综合修正后,利用量规函数和台站校正值重新计算烈度计震级,结果表明：在震中100 km范围内,烈度计测定震级偏差平均值由校正前的0.145降低至0.033,标准差由0.382降低至0.295,离散度减小;校正后的烈度计震级结果较优,说明本研究获得的量规函数和台站校正值更加适用于川滇地区烈度计台站的震级计算。     

Secondary Cones of the Shatsky Rise and Implications for Late-Stage Volcanism Atop Oceanic Plateaus

Oceanic plateaus are large igneous provinces in the oceans, created by massive underwater eruptions, but their late-stage volcanism is poorly understood. With the addition of recent high-quality bathymetric data to existing data, 286 secondary cones were discovered over Shatsky Rise oceanic plateau. These cones with steeper flank slopes(mean 6.1? ? 4.4?) and smaller sizes(102–1923 m in height) are morphologically distinct from the plateau, and they are thought to have formed after the main volcanic episodes. Cone height and characteristic height(420 m) are close to seamounts in the Pacific Ocean, whereas greater than those in the Atlantic Ocean. Mean flatness of Shatsky Rise's cones(0.25 ? 0.20) are similar to that of seamounts in both Pacific and Atlantic Oceans, but notably density in cone distribution(0.56 km-3) and their mean slope are significantly lower than those of seamounts in the two oceans. Lower slopes of secondary cones within Shatsky Rise may be explained by higher effusion rates of remaining magma. Although cone formation was expected to have a link to rifting by seafloor spreading, weak relationship between cone orientation and magnetic anomaly pattern implies that the expectation is negative. Moreover, weak correlation between the cone height and depth indicates it is not true that volcanic cones grow taller when they occur closer to the massif summits with thicker oceanic crust, which was suggested as the increase in hydraulic pressure. Cone height and flatness are also not strongly related, implying that remaining magma supply was too limited to foster the cones to critical height.     

内蒙古数字地震台网快速测定速报震级结果评估

利用2014—2018年内蒙古及邻省数字地震台网108个宽频带固定地震台站的事件波形数据,分别采用快速测定速报震级方法和常规速报震级测定方法对85例有效速报地震进行分析,测定两种方法的震级偏差,给出震级校正值,并对结果进行对比.结果表明:①快速测定法的结果与常规速报震级方法测定结果相比整体偏小,震级差绝对值介于0～0....     

Three carrier ambiguity resolution: distance-independent performance demonstrated using semi-generated triple frequency GPS signals

In spite of significant research in the development of efficient algorithms for three carrier ambiguity resolution, full performance potential of the additional frequency signals cannot be demonstrated effectively without actual triple frequency data. In addition, all the proposed algorithms showed their difficulties in reliable resolution of the medium-lane and narrow-lane ambiguities in different long-range scenarios. In this contribution, we will investigate the effects of various distance-dependent biases, identifying the tropospheric delay to be the key limitation for long-range three carrier ambiguity resolution. In order to achieve reliable ambiguity resolution in regional networks with the inter-station distances of hundreds of kilometers, a new geometry-free and ionosphere-free model is proposed to fix the integer ambiguities of the medium-lane or narrow-lane observables over just several minutes without distance constraint. Finally, the semi-simulation method is introduced to generate the third frequency signals from dual-frequency GPS data and experimentally demonstrate the research findings of this paper.     

涉海工程水下冲击打桩噪声测量方法研究

随着海洋、湖泊、河流和港口等人类活动逐渐增加,涉海工程产生的水下噪声污染及对海洋生物影响已引起广泛关注。工程建设期环境影响评价中,水下噪声测量逐渐成为海洋监管的要素。水下冲击打桩是工程建设中常见的低频水下脉冲声源,能够传播较远距离。如何规范地开展水下冲击打桩噪声测量至关重要。文章给出了水下冲击打桩噪声的通用测量方法,包括声学指标、测量系统、测量布放、声学测量配置、测量不确定性等,可为海洋工程建设影响评价、海洋生物生态保护等提供技术支撑。     

Pore Structure Heterogeneity of the Xiamaling Formation Shale Gas Reservoir in the Yanshan Area of China: Evaluation of Geological Controlling Factors

Micro-heterogeneity is an integral parameter of the pore structure of shale gas reservoir and it forms an essential basis for setting and adjusting development parameters. In this study, scanning electron microscopy, high-pressure mercury intrusion and low-temperature nitrogen adsorption experiments were used to qualitatively and quantitatively characterize the pore structure of black shale from the third member of the Xiamaling Formation in the Yanshan area. The pore heterogeneity was studied using fractal theory, and the controlling factors of pore development and heterogeneity were evaluated in combination with geochemical parameters, mineral composition, and geological evolution history. The results show that the pore structure of the reservoir was intricate and complicated. Moreover, various types of micro-nano scale pores such as dissolution pores, intergranular pores, interlayer pores, and micro-cracks are well developed in member 3 of the Xiamaling Formation. The average porosity was found to be 6.30%, and the mean value of the average pore size was 4.78 nm. Micropores and transition pores provided most of the storage space. Pore development was significantly affected by the region and was mainly related to the total organic carbon content, vitrinite reflectance and mineral composition. The fractal dimension, which characterizes the heterogeneity, is 2.66 on average, indicating that the pore structure is highly heterogeneous. Fractal dimension is positively correlated with maturity and clay mineral content, while it is negatively correlated with brittle mineral content and average pore size. These results indicate that pore heterogeneity is closely related to thermal history and material composition. Combined with the geological background of this area, it was found that the pore heterogeneity was mainly controlled by the Jurassic magmatism. The more intense the magma intrusion, the stronger the pore heterogeneity. The pore structure and its heterogeneity characteristics present today are a general reflection of the superimposed geological processes of sedimentary-diagenetic-late transformation. The influence of magmatic intrusion on the reservoir is the main geological factor that should be considered for detailed evaluation of the Xiamaling Formation shale gas reservoir in the Yanshan area.     

广州市人行天桥叶面滞尘粒度特征及其来源

对2009 年广州城区36 座人行天桥上采集的植被叶面滞尘样品进行粒度分析,粒度结果显示：叶面滞尘多为沙质粉沙,粉沙、沙和黏土体积分数的平均值分别为53.99%、41.34%和4.67%;粒度频率分布呈三峰型,主峰态在10~200 μm 之间。4 个市辖区叶面滞尘的粒度特征都较为相似,说明整个广州城区的叶面滞尘在成因和来源上都较为一致。叶面滞尘中的总悬浮颗粒物（TSP≤100 μm）体积分数极高,PM2.5 和PM10 体积分数略低;PM2.5/PM10 的平均值为0.36,推测其更多来自道路扬尘与建筑扬尘等局地污染源。风沙动力研究指示：其物源主要是由城区30km范围内短距离悬浮搬运而来,属内源性颗粒物。     

Tidal effects on diel variations of picoplankton and viruses in the Changjiang estuary

Spatial distributions and seasonal variations of picoplankton (i.e. Synechococcus spp., Prochlorococcus spp., picoeukaryotes and heterotrophic bacteria) and viruses in the Changjiang estuary have been reported in the past. However, short-term variations (e.g. at a tidal timescale) of these organisms and their regulating factors remain unclear. We determined the time-series of fluctuations of picoplankton and viruses with tide simultaneously in flow cytometry in the Changjiang estuary during a cruise in June 2006, in which a tidal model based rectangle equation was applied. The results indicate that high cell abundances of picoplankton and viruses occurred during flood tide and low cell abundances during ebb tide. The period of the surface cell abundance variations was about 13 h, suggesting the surface cell abundances in the Changjiang estuary were largely regulated by tide. However, cell abundances in middle and bottom waters varied in different periods due to influences of tidal induced physical forces such as resuspension and stratification. Therefore, tidal action is an important factor for the diel variations of picoplankton and viruses in the Changjiang estuary.     

极低频海洋噪声与风的相关性研究

风通过影响海洋表面从而产生200 Hz以上的深海环境噪声,但有研究指出,通过风生表面波之间的非线性相互作用产生的驻波,能够与海床共振构成海底微震,从而产生10 Hz以下的噪声。针对这一新型风生噪声机制,本研究对威克岛海域10 Hz以下的极低频噪声进行了分析。比较了不同频率下海洋环境噪声功率谱级与风速的相关性,并讨论了风速和风向对设立在威克岛南北部二组水听器三联体信号的影响,结果表明2 Hz处的海洋环境噪声级与风速相关性最好,而风速和风向变化越剧烈海洋环境极低频噪声与风速风向的相关性越好。