Hazard analysis of seismic submarine slope instability

To assess the risk associated with a submarine landslide, one must estimate the probability of slope failure and its consequences. This paper proposes a procedure to estimate the probability of earthquake-induced submarine slope failure (hazard) based on probabilistic seismic hazard analyses, ground response analyses and advanced laboratory tests. The outcomes from these analyses are treated in a probabilistic framework, with analytical simulations using mathematical techniques such as the first-order reliability method, Monte Carlo simulation and Bayesian updating. Fragility curves of slope failure during the earthquake (co-seismic) and after the earthquake (post-seismic) were developed in this study, and were shown to provide a clear and well-organized procedure to estimate the annual failure probability of a submarine slope under earthquake loading.     

Structural changes during microstructural development in natural salt samples

This paper presents the microstructural and structural properties of two natural salt samples from Iran and Portugal. Their strength-ductility behavior is explored by uniaxial compression experiments that, demonstrate that the observed differences lie not only in the inhomogeneous composition of the samples and their different grain sizes but also in their internal microstructural inhomogeneities. Microstructural inhomogeneities and substructural changes were observed with the SEM method (Scanning Electron Microscopy), the thin section microscope investigations and the EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy. EBSD (Electron backscattered diffraction) analyses show maximum in the [100] or [110] directions in the inverse pole figure. This demonstrates that recrystallization and grain growth processes took place together. A weak [111] texture sometimes observed nearby indicates that residual stress is still present in the recrystallized sample.Comparison of the textural and structural results show that local structural rearrangements take place during textural development; this is attributed to different orientations influencing the deformation and recrystallization of adjacent grains influencing the bulk final texture.     

An Assessment of Performance in the Routine Analysis of Silicate Rocks Based on an Analysis of Data Submitted to the GeoPT Proficiency Testing Programme for Geochemical Laboratories (2001–2011)

Data reported by laboratories contributing to the GeoPT proficiency testing programme for geochemical laboratories over the period from 2001 to 2011 have been assessed to identify the elements and concentration ranges over which analytical performance can be considered satisfactory. Criteria developed in the paper indicated that performance in the content determination of the elements/constituents SiO₂, Al₂O₃, MnO, Cs, Dy, Er, Eu, Ga, Hf, Ho, Lu, Nd, Pr, Sm, Sr, Tb, Tl, Tm, U, Y, Yb and Zn was satisfactory over the full concentration range assessed. The elements/constituents TiO₂, Fe₂O₃(T), MgO, CaO, Na₂O, K₂O, P₂O₅, Ba, Be, Cd, Ce, Co, Gd, La, Li, Nb, Rb, Sb, Sc, Sn, Ta, Th, V and Zr showed some degradation in performance at lower concentration levels (approaching the detection limit of some techniques). Performance in determining LOI, As, Bi, Cr, Cu, Ge, Mo, Ni, Pb and W was in general unsatisfactory over the full concentration range assessed. Other elements (especially Fe(II)O, H₂O⁺, CO₂, Ag, Au, B, Br, Cl, F, Hg, I, In, Ir, N, Os, Pd, Pt, Re, Rh, S, Se, Te) could not be evaluated as they were not routinely reported by laboratories participating in the GeoPT programme, often because they are present in silicate rocks at sufficiently low concentrations to require a pre‐concentration stage. Some suggestions are made for the causes of unsatisfactory performance, but further progress will require a detailed assessment of the methods used by participating laboratories, which will form the subject of a further paper.     

长江巫峡岸坡座滑式危岩稳定性研究——以望霞座滑式危岩为例

通过对长江巫峡望霞座滑式危岩调查研究表明,在川东平行岭谷一系列平行展布的背斜山、向斜谷的窄岭宽谷地貌格局控制作用下,长江巫峡横石溪背斜岸坡近水平的灰岩与页岩、泥岩软硬互层结构为座滑式危岩的孕育提供了有利条件;对危岩软弱基座矿物成分 X-Ray 衍射的结果表明,绿泥石、云母、蒙脱石等层状结构硅酸盐矿物含量较高,其抗剪强度低,容易产生滑动,易沿主控结构面方向形成潜在破坏面,导致岩体整体剪出,发生座滑破坏。根据危岩发育机理,将三峡地区座滑式危岩破坏过程归纳为四个阶段,即：拉裂阶段、扩展阶段、失稳阶段和后期破坏阶段;并基于极限平衡理论和岩体结构理论,推导了座滑式危岩破坏的两组结构面的应力表达式,建立了座滑式危岩稳定性分析的力学模型。将该方法运用到望霞座滑式危岩案例计算表明,天然状况下危岩稳定系数为1.19,属于基本稳定岩体;在饱和状态下,随后缘裂隙充水高度的增加其稳定系数递减,当裂隙充水高度为10 m 时,稳定系数为1.15,当裂隙充水高度为20 m 时,稳定系数为1.07。     

2013年甘肃岷县漳县6.6级地震触发滑坡及其构造分析

2013年7月22日,甘肃省岷县漳县交界发生了Ms6.6地震.地震触发了大量的、类型各种各样的滑坡.滑坡类型以黄土崖崩、滑、倾为主,还有一些深层连贯型土质滑坡、大型土质流滑、斜坡裂缝等类型.地震滑坡主要分布在一个与临潭-宕昌断裂平行的长条形区域内.该长条形区域面积约为250km2,长度约40km,最大宽度约8km.对应不同构造段落的区域内滑坡发育程度不同,反映了不同段落发震构造的特征差异.滑坡的主体分布范围与震中位置表明了构造破裂是从SEE向NWW方向发展的.最后,分析了该滑坡主体分布区中心线与临潭-宕昌断裂在空间地理位置上相差10km的2种可能的原因.     

Using Cooperative Water Quality Data for a Holistic Understanding of Rivers and Streams: A Study of the Neponset River,Massachusetts

Water quality studies seeking to identify modes or processes of river systems often use targeted, research-designed, high-frequency data, whereas most water quality data today are collected for monitoring and reporting requirements are of low frequency and are collected through cooperative and volunteer programs. There exists in this situation an information gap between the science of understanding river system dynamics and the collection of data in most of these systems. Using data collected by volunteers in the Neponset Watershed (Massachusetts, U.S.), we demonstrate that multivariate analysis is a viable option for enhancing the use and information of spatially distributed, long-term monitoring data sets common in the United States. Additionally, the geographic, environmental, and time line information inherent in these community-maintained data leads to a more complete picture of river and stream dynamics. Principal component analyses of three distinct reaches with different channel characteristics and surrounding environments demonstrate differences in dominant modes, with undeveloped stretches driven by seasonal processes, and other stretches exhibiting organic or nutrient sources. This type of information can bridge gaps from problem identification or monitoring to a more complete understanding of river system processes influencing water quality, thereby leading to better stewardship of resources.     

Environmental “Education”: The Last Measure Of Man

Promotion of nonacademic geography is a logical response to curtailment of opportunity for new teaching careers. Yet this necessary redirection of effort must be accompanied by renewed dedication to education and especially to nonprofessional undergraduate education. The case for geography in the liberal arts curriculum may well be a strong one, but questions about what we can offer need to be raised more frequently among ourselves if we are to respond effectively when such questions are asked by outsiders.     

Detrital zircon ages in Palaeozoic and Mesozoic basement assemblages of the Peninsular Ranges batholith,Baja California,Mexico: constraints for depositional ages and provenance

The origin and continuity of Phanerozoic lithostratigraphic terranes in southern and Baja California remain an unsolved issue in Cordilleran tectonics. We present data from eight detrital zircon samples collected across the southern extent of the Peninsular Ranges that help constrain the provenance of detritus and the depositional ages of these basement units. Detrital zircon signatures from units in the eastern Peninsular Ranges correlate with Palaeozoic passive margin assemblages in the southwestern North American Cordillera. Units in the central belt, which consists of Triassic–Jurassic metasedimentary turbidite assemblages that probably deformed in an accretionary prism setting, and Cretaceous metasedimentary and metavolcanic units that represent the remnants of a continental margin arc, were derived from both proximal and more distal sources. The westernmost units, which are locally structurally interleaved with the Triassic through Cretaceous units of the central belt, are Cretaceous deposits that represent a series of collapsed basin complexes located within and flanking the Cretaceous Alisitos volcanic island arc. Cretaceous intra-arc units show little influx of cratonal material until approximately 110 Ma, whereas coeval sediments on the northern and eastern flanks of the Alisitos arc contain abundant cratonal detritus. Intra-arc strata younger than approximately 110 Ma contain large amounts of Proterozoic and older detrital zircons. These data suggest that basins associated with the Alisitos arc were either too distant or somehow shielded from North American detritus before 110 Ma. In the case of the former, increased influx of continental detritus after 110 Ma would support a tectonic model in which the arc was separated from North America by an ocean basin and, as the arc approached the continent, associated depositional centres were close enough to receive input from continental sources.     

贵州省织金县四方井岩溶大泉断流原因浅析

本文通过对织金县城四方井岩溶大泉系统的岩溶发育规律、水文地质特征、地下水动力条件进行调查分析,认为织金县四方井岩溶大泉的突然断流与2010年西南特大干旱造成区域地下水位的急剧下降及位于主径流带上的高层建筑深基坑施工产生的动荷载导致的塌陷体堵塞地下水径流通道有着密切联系。     

Pronounced increase in slope instability linked to global warming: A case study from the eastern European Alps

In recent decades, slope instability in high-mountain regions has often been linked to increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small- to medium-sized mass movements in a high-elevation catchment of the Italian Alps (Sulden/Solda basin). We found that slope-failure events (mostly in the form of rockfalls) have increased since the 2000s, whereas the occurrence of debris flows has increased only since 2010. The current climate-warming trend registered in the study area apparently increases the elevation of rockfall-detachment areas by approximately 300 m, mostly controlled by the combined effects of frost-cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity-duration rainfall distribution. Potential debris-flow events in this environment may additionally be influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden/Solda basin (above ca. 2500 m above sea level [a.s.l.]), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 2000s, and that an increase in rockfalls and debris flows during spring and summer can be inferred. Our study thus confirms that “forward-looking” hazard mapping should be undertaken in these increasingly frequented, high-elevation areas of the Alps, as environmental change has elevated the overall hazard level in these regions.