Investigation of a large collapse sinkhole affecting a multi-storey building by means of geophysics and the trenching technique (Zaragoza city,NE Spain)

An active sinkhole around 100 m long has been investigated in the city of Zaragoza (NE Spain). Subsidence activity on this depression, including the sudden occurrence of a collapse sinkhole 5 m across, led to the abandonment of a factory in the 1990s. At the present time, a building with 100 flats and shallow pad foundations partially built on the sinkhole, is affected by rapid differential settlement. The development of the sinkhole results from the karstification of the halite- and glauberite- bearing bedrock and the sagging and collapse of the overlying bedrock and alluvium, more than 30 m thick. GPR and electrical resistivity profiles have provided information on the distribution and geometry of the subsidence structure. The application of the trenching technique and geochronological methods (AMS and OSL dating) has allowed us to infer objective and practical data on the sinkhole including (1) Limits of the subsidence structure, (2) subsidence mechanisms, (3) cumulative subsidence (>408 cm), (4) subsidence rates on specific failure planes (>1.8 cm/year), (5) episodic displacement regime of some fault planes. The available information indicates that the progressive deformation recorded in the building will continue and might be punctuated by events of more rapid displacement. This work illustrates the practicality of the trenching technique for the study of sinkholes in mantled karst areas.     

Acoustic behaviour of southern right whales in relation to numbers of whales present in Walker Bay,South Africa

Estimating numbers of whales present in an area from recorded call rates could be a useful conservation tool. We recorded southern right whale Eubalaena australis vocalisations and presence in Walker Bay on the south coast of South Africa. In all, 45 sessions with synchronous acoustic and visual data were analysed to determine call rates directly (overall call rate, OCR) and in relation to the number of whales sighted (call rate per whale, CPW) and number of groups sighted (call rate per group, CPG). The OCRs were examined in the presence of varying numbers of whales, using a log-linear model to investigate the dependence of the call rate on whale density. The number of whales present exerted a strong quadratic effect on the OCR, which peaked at around 15 whales and decreased to a low rate as whale presence approached a maximum, for all calls combined and for four of their constituent 13 call types: a quadratic trend was present to varying degrees among the remaining call types. Both quadratic and linear trends were absent when OCR was assessed against number of groups present, possibly because group size increased with increasing density of whales. A linear regression on the CPW and CPG suggested that there was a negative inverse relationship with the number of whales and groups present respectively. These findings are important in that, while they preclude the estimation of absolute numbers from call rates, they imply that, under the conditions prevailing in Walker Bay, southern right whales were aware of the presence, arrival and departure of other animals in their vicinity and adjusted their vocal behaviour accordingly.     

Marine protected areas in Australia: Towards a coordinated rock lobster industry position

Plans by government to accelerate the establishment of a national representative system of marine protected areas (NRSMPAs) in Australia have caused increasing disquiet within the fishing industry. Rock lobster fishers have raised concerns regarding plans to establish large “multiple‐use” MPAs that may or may not contain a substantial no‐take component in the continental shelf waters adjacent to the coast. Key industry concerns including the potential impacts on present and future harvest rates are examined. The industry response to government MPA policy in each of the major jurisdictions is outlined. An industry position developed at the National Rock Lobster Congress in Perth, Western Australia (September 2003) is put forward. The position advocates the need for an adjustment scheme to account for displaced effort, the need for government commitment to the development of management plans that include the long‐term monitoring of all MPAs, and the need for a thorough risk assessment process to be conducted before the establishment of an MPA. The issues raised in this paper should be relevant to the establishment of MPAs in an international context.     

Surface lowering of limestone pavement as determined by cosmogenic (36Cl) analysis

Determination of the rate and total amount of limestone pavement surface lowering is a critical issue in developing models of regional landscape change in limestone terrain. Erratic‐capped pedestals have frequently been used for this purpose but problems concerning definition and measurement of pedestal height, and the absence of a secure timeframe for erratic emplacement, have resulted in conflicting interpretations. We have used cosmogenic (³⁶Cl) to establish the emplacement age of erratic boulders and the total amount of pavement surface lowering at sites in northwest England. Since erratic emplacement at 17.9 ka the limestone pavement has been lowered by 22–45 cm (average: 33 ± 10 cm), assuming lowering was continuous. Although indicating some spatial heterogeneity, the results contrast with earlier reported values based on the measurement of pedestal heights and inferred age for deglaciation. We consider that changes in climate and the character and duration of regolith covers to have been important influences in promoting surface lowering. It is argued that nivation (chemical and mechanical snow‐related processes) associated with several cool/cold periods is likely to have played an important role in surface lowering. Complicating factors associated with surface lowering (thickness and longevity of snow and regolith covers) are identified but as yet cannot be quantified. Copyright © 2012 John Wiley & Sons, Ltd.     

Sewage treatment level and flow rates affect polychaete assemblages

The European Water Framework Directive (WFD) and the Urban Wastewater Treatment Directive (UWWTD) aim to improve water quality and reduce the environmental impact of wastewater, by requiring member states to introduce better treatment levels. This study was carried out in order to detect the most suitable treatment type or flow level for reducing benthic environmental impact. Therefore, soft-bottom polychaete assemblages affected by discharges of six treatment plants, with different treatment technologies and flow rates, were analysed over three consecutive years. Polychaete assemblages changed as a result of sewage discharge. These changes were related to treatment level and flow rates. Both disposal quality and quantity are important since changes in soft-bottom assemblages in stations affected by pre-treated sewage with medium and high flow rates are observed. However, the location with a low-flow pre-treated effluent has similar polychaete assemblages with regard to locations with biological treatment or controls.     

The transport-geographical location of Siberia's microregions: techniques and assessment results

It is established that the methodological tools for quantitative measurement of the transport-geographical location is insufficiently advanced. We suggest the algorithm for the technique of its cost assessment based on determining the “economic” distances and adapted to the peculiarities of the transport system of Siberia. We calculated the costs of the transport-geographical location of Siberian microregions (within administrative districts) with respect to the most important year-round sea ports for the current (the year 2005) and future (the year 2030) levels.     

Discussion on the Abnormally Low Active Fault Slip Rate of the M_S 8. 0 Wenchuan Earthquake

Based on the collection of active fault slip rate data of large intra-continental shallow thrust earthquakes occurring in the triangular seismic region of the East Asia continent,a preliminary analysis has been performed with results showing that the Wenchuan,Sichuan, China earthquake ( MS = 8. 0) of May 12,2008 occurred on the Longmenshan Mountain active fault with an abnormally low slip rate.     

不同风化程度花岗岩动力特性实验研究

采用6种不同风化程度的花岗岩试样,在相同围压下进行了不同加载速率（1～105 MPa/s）的动三轴压缩实验。研究发现,不同风化程度花岗岩试件的抗压强度、弹性模量均随加载速率的增加而增加,泊松比随加载速率的增加而减小。抗压强度的增加幅度随风化程度的增加而增加,弹性模量的增加幅度基本保持不变     

不同砾石覆盖度戈壁床面风蚀速率定量模拟

通过风洞实验,利用称重传感器自动记录风蚀观测样方重量变化过程,对供沙条件下不同砾石覆盖度戈壁床面风蚀速率进行了定量模拟研究。结果表明:砾石覆盖度是影响戈壁风蚀速率的关键因子,戈壁床面风蚀速率随砾石覆盖度增加按指数规律递减。各实验风速下,砾石覆盖度>50%时,戈壁床面风蚀速率随砾石覆盖度增加而减小量有限,甚至无风蚀发生;而盖度从10%到50%时,风蚀速率显著减小。因此,两种实验粒径砾石(3 cm与4 cm)至少在50%盖度时才能达到较好的风蚀防治效果。戈壁风蚀防护机理主要是砾石覆盖度的增加增大了砾石间沙粒的临界起动剪切风速,而且减少了作用在砾石间可蚀地表的剪切压。与沙质对照床面相比,10%~90%砾石盖度戈壁床面沙粒临界起动剪切风速增大了0.8~3.4倍,只有0.5％~28%的剪切压作用在砾石间可蚀地表。