P波斜入射角对沉管隧道地震响应的影响

为了研究P波斜入射对沉管隧道地震响应的影响,以港珠澳大桥沉管隧道为工程背景,考虑上覆海水与海床、沉管隧道之间耦合作用,采用粘弹性边界和等效力的地震荷载输入方式,利用ADINA软件建立三维有限元模型进行地震响应分析。分析入射角为0°、20°、40°、50°、60°时P波对沉管隧道环向应力峰值（正应力峰值、剪应力峰值）和位移峰值的影响,结果表明:入射角为40°时,沉管隧道应力峰值最大;入射角为0°—40°时,隧道的应力峰值逐渐增大,入射角为40°—60°时,隧道的应力峰值逐渐减小;隧道截面4个转角处及隔墙与顶板、底板的连接处为隧道剪应力峰值最大处;隧道截面左侧剪应力峰值远大于右侧;隧道顶板正应力峰值最大,顶板的正应力峰值大约为底板的2倍;隧道截面左侧位移峰值远大于隧道截面右侧。     

测氡仪标准仪器校准法的可行性研究

针对目前台站测氡仪校准困难的问题,提出标准仪器校准法,并将其与RN-FD循环式氡气固体源进行对比,同时利用台站应用最为广泛的RN-150小型氡气固体源验证该方法的可行性。结果表明,利用RN-150小型氡气固体源及AlphaGUARD P2000F标准仪器分别对FD-125测氡仪3个闪烁室进行校准后得到的校准系数相对误差分别为0.2%、3.4%、2.8%,均达到目前地震监测中氡观测的技术要求,进一步验证了测氡仪标准仪器校准法的可行性。     

ROSAT HRI observations of P Cyg and surrounding area

We present a detailed analysis of deep ROSAT HRI observations of the luminous blue variable P Cyg and its surrounding radio nebula. The HRI image provides a point source at the position of P Cyg. However, we show that this emission can be attributed to the ultraviolet leak of the ROSAT HRI. The X‐ray flux upper limit derived from the HRI data of this star is discussed in the context of X‐ray emission from hot stars. Furthermore, we present a search for diffuse X‐ray emission possibly associated with the radio nebula surrounding P Cyg. We compare our results to model predictions and X‐ray fluxes observed for shells around other hot stars. Additionally, we detect 10 X‐ray sources in the field of view. All but one of these X‐ray emitters have stellar counter parts in the Palomar Sky Survey. We suggest that they are active late‐type stars possibly belonging to Cyg OB1.     

三峡水库消落区典型草本植物氮、磷养分计量特征

为明确消落区土壤养分对植物生长的影响,通过室内栽培试验,研究三峡库区秭归消落区土壤3种氮磷水平下4种草本植物—鬼针草(Bidens pilosa)、苍耳(Xanthium sibiricum)、水蓼(Polygonum hydropiper)、藜(Chenopodium album)长势及氮、磷计量特征.结果表明,消落区土壤中生长的植物氮含量为7.98~19.4 mg/g,磷含量为0.740~3.880 mg/g,氮磷比为3.48~13.70,判别植物生长受氮限制.外源氮磷的添加促进植物氮、磷含量明显升高,但氮磷比没有明显变化;外源氮磷添加解除植物受氮的限制作用.4种植物对消落区土壤低氮环境具有一定的适应能力.比较消落区土壤中4种植物长势,鬼针草生物量、相对生长率、根茎生物量比最高,氮磷养分丰富对鬼针草生长促进作用最明显,表明鬼针草更易于在氮、磷贫乏的三峡库区消落区形成优势群落.     

VARIATION OF THE TRAVEL TIME DIFFERENCE BETWEEN TELESEISMIC PS CONVERTED WAVE AND PP TRANSMITTED WAVE IN FOCAL REGION BEFORE AND AFTER WENCHUAN MS8.0 EARTHQUAKE

When P waves from distant earthquakes meet a velocity discontinuity in the earth's crust and upper mantle, they give rise to a series of converted PS waves besides PP refracted waves. It is possible to monitor the variation of the physical properties of the medium in the limited formation space above the transition zone of the seismogenic zone by measuring the time difference between the teleseismic PS converted wave and the first arrival P wave, that is, time-variation Δt_PS=t_PS-t_P. The advantage of this method is that the transition point of the teleseismic source with similar source is relatively stable at the transition interface, and the accuracy of the measured relative time is high, and the change of the medium in a small range of the seismogenic zone above the conversion interface can be monitored. This paper studies the variation of the travel time difference Δt_PS in focal region before and after Wenchuan M_S8.0 earthquake. We select 2001 to 2012 as the research period, use teleseismic waveforms which occurred in the southern region of Sumatra and Hindu Kush area recorded by Sichuan station YZP and JJS. These teleseisms satisfy 5.0 ≤ M ≤ 6.5, and their waveform signal-to-noise ratio is high with clear initial P-wave motion. The epicentral distance of teleseisms is less than 3 degrees. Then we obtain the variation of the travel time difference Δt_PS between teleseismic PS converted wave and PP transmitted wave recorded during the study period in the two stations. The results show that there is a slow increasing trend of Δt_PS before 2006, and an obvious low value process of Δt_PS appeared in the period about 2 years before the Wenchuan earthquake. The maximum decline was about 0.2~0.3s, more than 4~5 times the measurement error. The low value has a certain degree of return about 2~3 months before the earthquake. The change of arrival time difference indicates that the medium is in different states in different periods of seismogenic process. The sharp decrease in Δt_PS from 2006 to January 2008 may be due to the strong disturbance caused by the stress accumulation of the medium. At this stage, the velocity of P wave and S wave increases with the increase of stress, and the increase of S wave velocity will result in the decrease of Δt_PS. The change of Δt_PS is greatly affected by S wave velocity, so Δt_PS appears to decrease rapidly. Regarding the low value that has a certain degree of return about 2~3 months before the Wenchuan earthquake, the possible reason is that the release of stress is much higher than the accumulation of stress in meta-instability stage. At this stage, the velocity of S wave decreases and the decrease of S wave causes Δt_PS to increase. Then, the Wenchuan earthquake of magnitude 8.0 occurred. It is shown that the teleseismic converted wave method in this paper can monitor the variation of medium's wave velocity before large earthquakes, and it has a good prospect in seismic monitoring and worth further experimental study.     

山西地区远震P波到时残差分布

收集2008—2016年山西地震台网记录的震中距30°—90°范围内1 253个远震事件波形,拾取7 600余条高质量P波初至到时,使用IASP91模型计算相对到时残差,分析残差水平分布特征,结果显示:①以山西地区中部的山西断裂带为界,西部地震台站记录的P波初至主要表现为早到时,东部位于大同火山区的地震台站记录则主要表现为晚到时;②位于山西断裂带内部的地震台站记录的P波初至主要表现为早到时,残差水平显著低于西部地震台站;③研究区P波到时整体呈现自西向东逐渐由早到晚的分布特征。推测山西断裂带西部地区下方可能存在高速异常结构,山西断裂带内部及大同火山区下方可能存在低速异常结构。     

安徽太平湖水库初级生产力时空分布及分析

安徽太平湖是2014年国家列入的重点保护湖泊之一,鉴于其生物本底资料的缺乏,于2012年11月至2014年10月,从上游至下游选取H1、H2、H3、H4、H5共5个样点,采用黑白瓶法对太平湖的初级生产力进行为期2年的调查研究.结果显示,太平湖水柱毛初级生产力、水柱净初级生产力和水柱呼吸量的平均值分别为4.54±6.72、-1.82±7.77和6.50±7.62 g/(m2·d).时间分布上,水柱毛初级生产力出现3个峰值,分别在2012年11月、2013年5月和2014年7月,呼吸量在2013年7月份出现远高于其他月份的峰值,达到了16.04 g/(m2·d),水柱毛初级生产力季节变化表现为夏季秋季春季冬季.太平湖初级生产力存在显著的空间差异,水平分布上毛初级生产力与呼吸量的水平分布相似,湖心H3样点最小,下游的H4、H5样点较高;垂直分布显示,毛初级生产力主要贡献在表层和1SD层,并沿水深逐渐降低,呼吸量的垂直分布与毛初级生产力不同,最高值出现在1SD和2SD层,各层净初级生产力的值均较小,无明显峰值或谷值.研究表明,太平湖水库水柱的P/R系数小于1,但最高生产力层(表层)的P/R系数大于1.相关分析显示水柱毛初级生产力与温度和湖深呈显著正相关,与其它环境因子相关性不明显.     

高氮磷比与酸化共同作用对微小亚历山大藻生长和产毒的影响

通过实验室构建不同氮磷比条件下的酸化海水环境,培养麻痹性贝毒(paralytic shellfish toxin,PST)产毒藻微小亚历山大藻(Alexandrium minutum),采用藻细胞计数法、分光光度法、高效液相色谱-质谱法等分析方法,探讨了不同氮磷比条件下的酸化海水对微小亚历山大藻的生长、氮磷营养盐吸收、产毒等参数的影响。结果表明,在一定程度上,酸化环境对A.minutum的生长、PST的胞内累积和胞外释放有促进作用,且胞外培养液中PST含量增加的程度更高;同时,酸化海水促进胞内毒性较低的N-H类膝沟藻毒素(GTX2和GTX3)被氧化成毒性较高的N-OH类膝沟藻毒素(GTX1和GTX4),导致A.minutum的细胞毒性和培养液毒性增加。而海水中氮磷比的进一步升高,在一定程度上促进了微小亚历山大藻细胞毒素含量和毒性的增加,但并未促进其生长,且降低了藻细胞内的磷储量。     

李四光和卡尔宾斯基金质奖章

中国地质学家李四光与当时苏联地学界来往交流紧密,他对地质学的贡献得到了苏联地质学家的高度评价。1958年,苏联科学院全体大会选举李四光为苏联科学院院士,并授予卡尔宾斯基金质奖章;该奖章是1947年由当时的苏联科学院和俄罗斯科学院共同发起的、对地质科学有突出贡献的科学家最高单人奖励,李四光是第六位获奖人,也是至2017年止唯一获此殊荣的外籍地质学家,他的获奖理由是:在地质、古生物、地层和矿产研究工作的综合贡献。李四光有两部著作在苏联被译成俄文出版,分别是1952年的《中国地质学》和1958年的《中国西北部的旋卷构造》,这两部译作对当时的苏联地质界产生了很大影响,极大地推动了李四光学术思想的广泛认知;"地质无国界",中国地调百年的发展历程也有着俄罗斯地学理论、规范、方法实践的烙印,在新的"一带一路"合作倡议和李四光学术精神传承下,中俄、中国与中亚在地学领域的交流合作将不断深化,硕果累累。      

不同氮、磷浓度及配比对铜藻(Sargassum horneri)幼苗生长的影响

采用铜藻(Sargassum horneri)幼苗为实验对象,分别以Na NO3和Na H2PO4为氮源和磷源,研究了不同氮磷质量浓度及氮磷配比对铜藻幼苗生长的影响。进行了氮、磷单因子实验、双因子实验以及不同氮磷配比实验,实验时间为8d。结果表明:氮和磷对铜藻幼苗生长影响极显著(P0.01),且当氮、磷的质量浓度分别为8mg/L、0.4mg/L时,铜藻幼苗的特定生长率最大;交互作用影响不显著(P0.05),不同质量浓度的氮为主效应;不同氮磷质量浓度比影响极显著(P0.01),且当氮磷比为10:1时,铜藻幼苗的特定生长率最大。研究结果为铜藻幼苗培育过程中营养盐的合理调控提供了理论依据。