大姚、姚安地震数字记录波形分析

通过对大姚、姚安地震中永胜台数字地震记录波形变化的分析研究,发现在大姚地震后一段时间里,P波初动出现“大头波”现象,而姚安地震后则没有出现明显的“大头波”,并且也没有再发生Ms≥5．0级地震,从而联想到震后强余震的出现是否会与数字记录中“大头波”的出现存在某种关系。     

Space–time multiresolution atomistic visualization of MgO and MgSiO3 liquid data

First-principles molecular dynamics simulations of complex material systems such as geophysically relevant oxide and silicate liquids produce massive amounts of time-varying three-dimensional data for the atomic configurations. Given the high accuracy of these data, it is desirable to extract as much information hidden in the data as possible. In this paper, we elaborate on our recently proposed scheme to support interactive visualization at space–time multiresolution of the atomistic simulation data. Instead of just focusing on direct rendering of the given data, additional data (containing more quantitative and qualitative information) that usually have to be extracted by some other means are extracted and rendered on the fly. This allows us to gain better insight into the global as well as local spatio-temporal behavior of the data in the context of bonding, radial distribution, atomic coordination, clustering, structural stability and distortion, and diffusion. We illustrate such visualization for the simulation data on the liquid phases of MgO and MgSiO₃—the two most abundant components of Earth’s mantle. Our analysis shows that the structure and dynamics of both liquids change substantially with compression, with no discernible effects of temperature in most cases.     

From fishing to farming: Shellfish aquaculture expansion and the complexities of ocean space on Canada's west coast

Ocean spaces are social and political, and just as with terrestrial governance, oceans governance is prone to ambiguity, contradiction, and contestation. The validity and dynamics of these claims will be demonstrated through a study of discourse and structured agreements employed to involve coastal First Nations in the expansion of the shellfish aquaculture sector in British Columbia. Analysis focuses on the West Coast of Vancouver Island, a region identified as having good biophysical potential for shellfish aquaculture and much of which is territorial home of the Nuu-chah-nulth First Nations. Through community interviews and document and discourse analysis, the article highlights that: seafood, including shellfish, is intimately connected with Nuu-chah-nulth identity; many Nuu-chah-nulth have long-engaged in subsistence and commercial harvests of wild-growing shellfish; and, there are important prospective differences between longer-standing shellfish harvests and shellfish aquaculture. Findings and discussion offer perspective on the sorts of choices that First Nations might encounter in the pursuit of shellfish aquaculture, as well as raise bigger questions about whether or how Nations might tradeoff territorial authority and collective harvest opportunities against leasing state-sanctioned private marine tenures.     

The impacts of food price and income shocks on household food security and economic well-being: Evidence from rural Bangladesh

This paper examines the combined impacts of food price and income shocks on household food security and economic well-being in low-income rural communities. Using longitudinal survey data of 1800 rural households from 12 districts of Bangladesh over the period 2007–2009, we estimated a three-stage hierarchical logit model to identify the key sources of household food insecurity. The first-difference estimator was then employed to compare pre- and post-shock expenditure for those households that experienced acute food shortages and those that managed to avoid the worst impacts of the shocks. On the basis of our results we conclude that: (1) the soaring food prices of 2007–2009 unequivocally aggravated food insecurity in the rural areas of Bangladesh; (2) the subsequent income shocks of 2007–2009 contributed toward worsening food insecurity; (3) the adverse impacts of these shocks appeared to have faded over time due to labor and commodity market adjustments, regional economic growth, and domestic policy responses, leaving no profound impacts on households’ economic well-being in most cases; and (4) although the immediate adverse consequences of rising food prices were borne disproportionately by the poor, the longer term consequences were distributed more evenly across the rich and poor and were favorable for the day laborers.     

原观测场时间序列两个统计场的相似性讨论

一些研究认为,原观测场时间序列的第一特征向量场与时间平均场表现出强相似。经研究得出,原观测场时间序列的这两个统计场间存在本质差异。它们的相似性依赖于原观测场时间序列在相空间中的结构。时间平均场（气候场）与时间偏差（异常）场集的相对强弱在二者相似与否中起到重要作用。     

http://www.sciencedirect.com/science/article/pii/S1674987112001065

It has been thought that granitic crust,having been formed on the surface,must have survived through the Earth’s evolution because of its buoyancy.At subduction zones continental crust is predominantly created by arc magmatism and is returned to the mantle via sediment subduction,subduction erosion, and continental subduction.Granitic rocks,the major constituent of the continental crust,are lighter than the mantle at depths shallower than 270 km,but we show here,based on first principles calculations, that beneath 270 km they have negative buoyancy compared to the surrounding material in the upper mantle and transition zone,and thus can be subducted in the depth range of 270-660 km.This suggests that there can be two reservoirs of granitic material in the Earth,one on the surface and the other at the base of the mantle transition zone(MTZ).The accumulated volume of subducted granitic material at the base of the MTZ might amount to about six times the present volume of the continental crust.Our calculations also show that the seismic velocities of granitic material in the depth range from 270 to 660 km are faster than those of the surrounding mantle.This could explain the anomalous seismic-wave velocities observed around 660 km depth.The observed seismic scatterers and reported splitting of the 660 km discontinuity could be due to jadeite dissociation,chemical discontinuities between granitic material and the surrounding mantle,or a combination thereof.     

滇西北丽江地区石鼓古湖的发现及其在现代金沙江河谷发育中的意义

在云南石鼓"长江第一湾"附近河段两岸发现了10多处典型的第四纪湖相沉积物露头,它们构成了金沙江第二、三、四级阶地的基座。热释光(TL)和U系法年龄测定及磁性地层学研究结果表明,该套湖相沉积物中上部的时代属于243.3～88.0kaBP的中更新世晚期至晚更新世早期,上覆的第四级阶地沉积物的年龄为88.0～80.9kaBP。湖相沉积物的粒度、地球化学和粘土矿物分析结果表明,其沉积环境有由温湿向湿热转化的趋势。根据对玉龙雪山更新世冰川作用的研究,石鼓古湖最初应是玉龙雪山西麓中更新世早期玉龙冰期冰碛物堰塞金沙江河谷而成的,中更新世晚期丽江冰期的冰水沉积物进一步加以堰塞,直至8万多年前被金沙江侵蚀而再次贯通。     

松南上白垩统青山口组一段不同赋存状态页岩油定量评价

松辽盆地南部青山口组一段页岩油资源丰富,多口井试油获得工业及高产油流,具有较大的勘探开发潜力。本文以青山口组一段下段为研究对象,以页岩油赋存状态为切入点,重点针对研究区页岩油富集优质岩相,即高有机质薄片状页岩和中有机质纹层状页岩中溶胀油、吸附油以及游离油量进行定量评价,揭示页岩油在地下页岩层系储层中的赋存特征。青山口组一段页岩油主要以干酪根溶胀态、干酪根吸附态、有机质孔隙游离态、无机矿物吸附态及无机孔隙游离态等5种赋存形式存在于页岩层系储层中。其中：高有机质薄片状页岩中页岩油赋存状态以干酪根溶胀油、干酪根吸附油和有机质孔隙游离油等有机赋存油为主,有机赋存油量可高达253.0 mg/g TOC,以TY1井页岩油赋存量最大,其次为CY8井,H238井页岩油量最低;中有机质纹层状页岩中页岩油赋存状态以无机矿物吸附油、无机孔隙游离油等无机赋存油为主,可达167.0 mg/g TOC,CY8井页岩油赋存量最大,H258井次之,H238井页岩油量最低。TY1井、CY8井位于半深湖—深湖区,发育大套泥页岩;H238井位于三角洲外前缘,离物源区较近,导致其页岩油赋存量明显低于半深湖—深湖区。因此,沉积环境是导致不同工区页岩油赋存量差异的主要原因。     

一种新的TOVS大气湿度反演方法及试验

利用国家气象中心的数值天气预报（NWP）6 h预报场。作为同步物理反演模式初估场，由气象卫星垂直探测（TOVS）资料推导出大气湿度，并给出了试验结果。结果表明，TOVS湿度反演的相对误差（RMS）约为20%。其中，夏季反演结果略优于冬季，而且低层（1000 hPa）和高层（500 hPa以上）与初估场相比有较大的改进，中层（850，700 hPa）二者大致相当。与统计回归反演结果相比其精度约提高10%。该研究为在我国建立“卫星反演/数据同化/数值预报”相互影响的循环系统奠定了基础     

2018年9月4日伽师5.5级地震序列震源机制解及震源处应力场特征

本文采用新疆测震台网数字波形记录，利用CAP和P、S波初动和振幅比方法计算2018年9月4日伽师5.5级地震序列中M_S≥2.5地震的震源机制解，结合地震烈度等震线和双差重定位后的地震序列空间展布等特征分析了此次地震的发震构造，反演了震源处应力场。结果表明，伽师5.5级地震呈NE向的节面I为发震断层面，属于左旋走滑断层，震源深度为9km，发震构造可能为浅部超基底断裂；地震序列中有21次为走滑型，4次为正断型，说明绝大多数序列的破裂方式与主震相近，表明余震应力场主要受主震震源应力场控制；P轴方位在NNE向有明显的优势分布且倾伏角较小，T轴方位在NWW向有明显的优势分布且倾伏角较小，说明震源处主要以NNE向水平挤压和NWW向水平拉张作用为主；此次伽师5.5级地震序列表现的浅部应力场与已有研究得出的震源区深部应力场基本一致，应力形因子R的最优解为0.17，说明震源处近NE向中间主应力σ₂有一定挤压成分。