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1.
A discrete element model to link the microseismic energies recorded in caprock to geomechanics 总被引：1，自引：0，他引：1
A discrete element model is presented to study slip-induced microseismic events along weak planes and crack-induced microseismic events within the intact rock for a representative elementary volume, REV, in the caprock of Weyburn reservoir. Also, the effect of varying factors such as orientation, coefficient of friction and elasticity of the weak plane on release of microseismic energies is studied. According to the results, for the conditions studied in this paper, the magnitudes of slip-induced events range from ~?1 to ?6, while crack-induced events range from ~?7 to ?11. Considering the capability of geophones, this suggests that events “recorded” in the caprock are more likely to have slip origins along weak planes than having crack origins within the intact rock. In order to show the applicability of the model in practice, the events recorded in the caprock of Weyburn from September to November of 2010 are analyzed. Also, a simple model is presented that correlates the amount of consumed energy per volume of the REV with the seismic energy released due to stick–slips along a weak plane. The results show that weak planes can be emissive even long before the failure of their surrounding is reached, and therefore, there can be a level of tolerance for the observed microseismic events in the caprock. 相似文献
2.
基于美国马里兰大学提供的海洋同化(SODA)月平均资料,用个例和合成分析方法,剖析了两类ENSO事件赤道太平洋海温异常演变特征。结果指出,东部型ENSO事件的初始海温异常源来自赤道西太平洋次表层,海温异常中心沿气候温跃层向东向上传送,至赤道东太平洋表层形成ENSO事件。东部型ENSO冷暖事件互为初始场,在形成某一位相的ENSO事件的过程中也同时为相反位相的ENSO事件准备条件。中部型ENSO事件的初始海温异常源出现在赤道中太平洋次表层,海温异常中心沿气候温跃层向东向上传送至赤道中东太平洋表层形成ENSO事件。中部型ENSO事件多在前次事件减弱中断后出现。 相似文献
3.
Since the nineteenth century scientists have tried to reproduce natural events in order to study and understand them through the technique of modelling. However, technology has evolved rapidly in the past two decades and now sophisticated numerical models are widely used to reproduce past events or simulate new scenarios. These models are particularly useful to reproduce the large scale and complexity of geological events. To illustrate the use and potential of numerical modelling in geological sciences, we describe a simulation of a large debris avalanche caused by the collapse of the north flank of the Taranaki volcano in New Zealand and the value of this information in the context of disaster planning. 相似文献
4.
The estuarine turbidity maximum (ETM) is an important nursery area for anadromous fish where early-life stages can be retained
in high prey concentrations and favorable salinities. Episodic freshwater flow and wind events could influence the transport
of striped bass (Morone saxatilis) eggs to the ETM. This hypothesis was evaluated with regression analysis of observational data and with a coupled biological-physical
model of a semi-idealized upper Chesapeake Bay driven by observed wind and freshwater flow. A particle-tracking model was
constructed within a numerical circulation model (Princeton Ocean Model) to simulate the transport of fish eggs in a 3-dimensional
flow field. Particles with the sinking speed of striped bass eggs were released up-estuary of the salt front in both 2-d event-scale
and 60-d seasonal-scale scenarios. In event scenarios, egg-like particles with observed specific gravities (densities) of
striped bass eggs were transported to the optimum ETM nursery area after 2 d, the striped bass egg-stage duration. Wind events
and pulses in river discharge decreased the number of egg-like particles transported to the ETM area by 20.9% and 13.2%, respectively,
compared to nonevent conditions. In seasonal scenarios, particle delivery to the ETM depended upon the timing of the release
of egg-like particles. The number of particles transported to the ETM area decreased when particles were released before and
during wind and river pulse events. Particle delivery to the ETM area was enhanced when the salt front was moving up-estuary
after river pulse events and as base river flow receded over the spawning season. Model results suggest that the timing of
striped bass spawning in relation to pulsed events may have a negative (before or during events) or positive (after river
flow events) effect on egg transport. Spawning after river flow events may promote early-stage survival by taking advantage
of improved transport, enhanced turbidity refuge, and elevated prey production that may occur after river pulse events. In
multiple regression analysis of observed data, mean spring freshwater flow rates and the number of pulsed freshwater flow
events during the striped bass spawning season explained 71% of the variability in striped bass juvenile abundance in upper
Chesapeake Bay from 1986 to 2002. Positive parameter estimates for these effects support the hypothesis that pulsed freshwater
flow events, coupled with spawning after the events, may enhance striped bass early-stage survival. Results suggest that episodic
events may have an important role in controlling fish recruitment. 相似文献
5.
红岩煤矿岩溶水对暴雨响应特征研究 总被引：1，自引：0，他引：1
岩溶地下水系统由于管道流和扩散流同时存在而非常复杂。岩溶区暴雨过程中矿井突水造成了生命与财产的重大损失，因此在这些地区掌握矿井突水对暴雨响应特征是极其关键的。本文在大量监测资料基础上研究了红岩煤矿岩溶地下水系统，利用时间序列频谱分析建立了突水与暴雨之间的响应模型，并利用该模型预测了矿井突水趋势。 相似文献
6.
the temporal and spatial evolution of seismicity, a simple cross-correlation technique was applied to a waveform data set of western Alps earthquakes. A selection of events recorded by a reference station of the regional seismic network of North-Western Italy (IGG network) within a particular S-P range was used. The adopted method was tested on 380 events recorded in 1995, allowing for the definition of the critical parameters for an optimal identification of earthquake families.The comparison of the individuated families definition with the relevant epicentres map confirms that, on small scales, the epicentre positions of microearthquakes located by a regional network could be strongly influenced by location errors. The analysis was extended to a more complete data set of 2653 events; 1171 of them were grouped in families. The results demonstrated that our single station method is able to discriminate between closely spaced families on the basis of the position and of the radiation properties. 相似文献
7.
Synoptic features associated with dust transition processes from North Africa to Asia 总被引：1，自引：0，他引：1
Aerosol index data from the total ozone mapping spectrometer satellite and reanalysis data from the National Center for Environmental Prediction and the National Center for Atmospheric Research are useful in the study of synoptic properties of the dust storms that carry dust from North Africa to Asia during the spring season for the period 1979 to 2006. In this study, we analyzed the synoptic properties of dust cases that pass through the transition zone between North Africa and Asia. We identified the dust cases to study by looking, inside transition zone, at events with an aerosol index greater than 2. We then divided the identified cases, depending on the spread and strength of the dust inside the transition zone, into seven categories ranging from weak events to moderate events to violent events. We found the common synoptic characteristics in all these categories as follows: The high pressure belt located over northern Africa allows the low pressure belt located over the South African Sahara to move northward; a pressure gradient between these two atmospheric systems directs from south to north; an increase in the pressure gradient leads to increased in both of the event’s dust and the amount of dust moves to North Africa from the Sahara; an additional pressure gradient between the western Azores high pressure system and the low pressure system located over the Arabian Peninsula directs from west to east; the stronger the pressure gradient, the greater the amount of dust in the event and moving a large amount of dust from Northeast Africa to Asia. To verify that these characteristics capture the essence of dust events from North Africa to Asia, we checked if they were also common to two additional extremes categories and two extremes events. The results confirmed the continued existence of these common characteristics. 相似文献
8.
Flood events, fatalities and damages in India from 1978 to 2006 总被引：1，自引：1，他引：0
High temporal and spatial variability of rainfall qualifies India to be highly vulnerable to floods. Recurring floods of various magnitudes play havoc with the lives and property of the people, leading to unplanned development and unchecked environmental degradation, thwarting and retarding the overall development of the country. Therefore, the purpose of the present study is to analyze the types and trends in terms of flood events, frequency, number of people killed, injured, missing and economic damage both in space and time on the basis of a nationwide database published by India Meteorological Department, Pune, from 1978 to 2006. Analysis of these long-term data has revealed that 2,443 flood events claimed about 44,991 lives with the average of 1,551 lives each year. In terms of population size, these figures translate into a loss of 1.5 human lives per million of the population. A majority (56 %) of flood fatalities were caused during severe flood events. However, the frequency of these events was just 19 % in comparison with heavy rainfall events (65 %). In spatial context, flood-related fatalities are distributed all over the country with highest fatalities in Uttar Pradesh (17 %), Maharashtra (13 %), and Bihar and Gujarat (10 % each). Most fatalities occurred during the summer season monsoon months of August (30 %) followed by July (29 %) and September (20 %). The country suffered a cumulative flood-related economic loss of about 16 billion US$ between 1978 and 2006 and a maximum economic loss of 1.6 billion US$ in the year 2000 alone. The study further suggests that both flood events and fatalities have increased in India over a period of time. 相似文献
9.
《Geoforum》2016
The cost of fire events can be devastating in human, emotional and financial terms. There is a growing realisation that geographical techniques can be used in cross-disciplinary approaches to gain an understanding of potential causation factors associated with such events. Despite this, the theoretical frameworks within which such research efforts are often couched have received relatively scant attention. Contrast this with literature concerned with the geography of crime where the application of routine activity theory in particular has been to the fore in studies concerned with providing a sound conceptual basis to understanding spatial and temporal analysis of crime events. This paper demonstrates the application of routine activity theory to understand the geography of fire events and identify ignition situations incited through behavioural regularities. Further, the paper illustrates the practical utility of routine activity theory and its extensions for designing targeted fire prevention, mitigation and response strategies. 相似文献
10.
Bingshun He Xianlong Huang Meihong Ma Qingrui Chang Yong Tu Qing Li Ke Zhang Yang Hong 《Natural Hazards》2018,90(1):407-420
Flash floods are one of the most disastrous natural hazards and cause serious loss of life and economic damage every year. Flooding frequently affects many regions in China, including periodically catastrophic events. An extensive compilation of the available data has been conducted across various hydroclimatological regions to analyze the spatiotemporal characteristics of flash floods in China. This inventory includes over 782 documented events and is the first step toward establishing an atlas of extreme flash flood occurrences in China. This paper first presents the data compilation strategy, details of the database contents, and the typical examples of first-hand analysis results. The subsequent analysis indicates that the most extreme flash floods originate mainly from small catchments over complex terrains and results in dominantly small- and medium-sized flooding events in terms of scales; however, these events, abrupt and seasonally recurrent in nature, account for a large proportion of the overall flooding-related disasters, especially disproportionately affecting elderly and youth populations. Finally, this study also recommends several immediate measures could be implemented to mitigate high impacts of deadly flash floods, although it still requires long-term significant efforts to protect human life and property in a country like China. 相似文献
11.
扬子地块西南部晚元古代--三叠纪沉积地球化学演化 总被引：2，自引：0，他引：2
本文通过对扬子地块西南部自上元古界板溪群到三叠系发育在盆地和下斜坡背景中的泥质岩的系统的无素地球化学研究，首次发现了下寒武统、上泥盆统和上二叠统这三个在元素地球化学性质上明显不同于其它层位的地球化学异常层，从而构成了本区地质历史中三个明显的地球化学旋回。通过地球化学旋回与本区地壳演化和一系列沉积事件之间关系的研究，发现它们之间存在着内在的必然联系，说明沉积地层的地球化学演化是地球发展演化的必然结果和物质表现形式。因此，可通过这些地层的元素地球化学体系来恢复地壳发育和演化历史，这为我们正确认识本区的地壳演化和成矿作用的时控性提供了强有力的地球化学证据. 相似文献
12.
Xiaoli Li Zhiqiang Li Jiansi Yang Yaohui Liu Bo Fu Wenhua Qi Xiwei Fan 《Natural Hazards》2018,90(2):843-861
The present study analyzes the runoff response during extreme rain events over the basin of Subarnarekha River in India using soil and water assessment tool (SWAT). The SWAT model is configured for the Subarnarekha River basin with 32 sub-basins. Three gauging stations in the basin (viz., Adityapur, Jamshedpur and Ghatshila) were selected to assess the model performance. Daily stream flow data are taken from Central Water Commission, India—Water Resources Information System. Calibration and validation of the model were performed using the soil and water assessment tool-calibration uncertainty programs (SWAT-CUPs) with sequential uncertainty fitting (SUFI-2) algorithm. The model was run for the period from 1982 to 2011 with a calibration period from 1982 to 1997 and a validation period from 1998 to 2011. The sensitivity of basin parameters has been analyzed in order to improve the runoff simulation efficiency of the model. The study concluded that the model performed well in Ghatshila gauging station with a Nash–Sutcliffe efficiency (NSE) of 0.68 during calibration and 0.62 during validation at daily scale. The model, thus calibrated and validated, was then applied to evaluate the extreme monsoon rain events in recent years. Five extreme events were identified in Jamshedpur and Ghatshila sub-basins of Subarnarekha River basin. The simulation results were found to be good for the extreme events with the NSE of 0.89 at Jamshedpur and 0.96 at Ghatshila gauging stations. The findings of this study can be useful in runoff simulation and flood forecasting for extreme rainfall events in Subarnarekha River basin. 相似文献
13.
The Bavarian Alps region is strongly affected by various natural hazards, mainly hydrological events (floods, debris flows),
geomorphic/geological events (landslides, rock falls), and avalanches. Extraordinary floods, like in 2002 or in the summer
of 2005 in south Bavaria, have again posed the question of the possible extent and frequency of recurrence of catastrophic
events. To put risk assessment on a broader basis historical data about all kinds of past natural hazards were detected in
the archives of local authorities and administrative offices for water management. More than 10,000 sources (written accounts,
maps, and photographs) were collated in a database. The majority of this information reaches back to the middle of the 19th
century. In addition, many documents referring to events dating back even as far as the middle age were found. The Historische
Analyse von NaturGefahren (HANG, historical analysis of natural hazards) project at the University of Eichstaett mainly focuses
on a small-scale examination of the data. Initial results of the data analysis show that most catastrophic events in the Bavarian
Alps only affect parts of the area, but not the whole region. Therefore it is necessary to assess the risk potential on a
local scale like valleys, the catchment areas of mountain streams, or even single streams. Firstly the presented data is aimed
to help engineers in future planning of hazard-protection measures. Secondly the information can form a vital component to
enhance our knowledge of hydrological and geomorphic/geological dynamics in the Alps. 相似文献
14.
Remote sensed data for automatic detection of land-use changes due to human activity in support to landslide studies 总被引：1，自引：1，他引：1
Slope instability studies appear to recognize a number of potential superficial slide-producing agents, which may be directly
detected and monitored with Earth Observation (EO) data. The main objective of this work is to use conventional EO data and
automatic techniques for providing land-use change maps useful in landslide prevention. The idea is to use the detection of
changes in areas already involved in landslide events as a precursory sign of variations in the equilibrium status of the
slope, independently from other natural triggering events, such as rain and seismic events. Attention is focused on man-induced
surface changes, such as deforestation, urban expansion and construction of artificial structures.
A historical set of 20 multi-temporal Landsat TM images, covering the period 1987–2000, was analyzed using a supervised change
detection technique on a test site affected by slope instability phenomena located in the Abruzzo region in Southern Italy.
A change image is obtained by comparing year-specific thematic map pairs. It contains useful information not only on the place
where a transition occurred, but also on the specific classes involved in the transitions between two different years. The
full set of change images is used to extract class-conditional transition probabilities, to evaluate variations in specific
class distribution and the total number of changed pixels in time. Four classes and their transitions were considered in the
analysis: (1) arboreous land, (2) agricultural land, (3) barren land, and (4) artificial structures.
The quantitative analysis of the class-joint transition probability values of some specific class-transitions that may worsen
slope stability showed that in an area prone to landslides the probability of landslide re-activation or first activation
is higher where changes have occurred. Although based on a limited number of known events, such a result encourages extensive
experimentation of the proposed technique on better documented landslide test sites. 相似文献
15.
Combining Knowledge from Diverse Sources: An Alternative to Traditional Data Independence Hypotheses 总被引：19，自引：0，他引：19
A. G. Journel 《Mathematical Geology》2002,34(5):573-596
Consider the assessment of any unknown event A through its conditional probability P(A | B,C) given two data events B, C of different sources. Each event could involve many locations jointly, but the two data events are assumed such that the probabilities P(A | B) and P(A | C) can be evaluated. The challenge is to recombine these two partially conditioned probabilities into a model for P(A | B,C) without having to assume independence of the two data events B and C. The probability P(A | B,C) is then used for estimation or simulation of the event A. In presence of actual data dependence, the combination algorithm provided by the traditional conditional independence hypothesis is shown to be nonrobust leading to various inconsistencies. An alternative based on a permanence of updating ratios is proposed, which guarantees all limit conditions even in presence of complex data interdependence. The resulting recombination formula is extended to any number n of data events and a paradigm is offered to introduce formal data interdependence. 相似文献
16.
Pacific Island countries are among the list of countries that face the highest disaster risk globally—in per capita terms. In recent years, governments in the region have been confronted by a rise in damages from extreme catastrophic events, many increasingly linked to climate change. These events pose significant challenges to Pacific governments in terms of maintaining fiscal stability and the operation of their limited and under-diversified economies and shallow financial sectors. Governments in the region generally play a leading role in domestic economies and are responsible for leading disaster prevention, mitigation, and recovery efforts. Accordingly, measures to improve financial sustainability and the public sector’s ability to provide public services in the aftermath of major disasters must be prioritized. This paper examines the literature on fiscal resilience to disasters, the estimated impacts of major events in the Pacific, and analyses the applicability of available financial instruments to facilitate both ex ante and ex post disaster fiscal risk management in the region. The paper also discusses policies that can improve resilience against fiscal risks.
相似文献17.
João Magalhães Neto Heliana Teixeira Joana Patrício Alexandra Baeta Helena Veríssimo Rute Pinto João Carlos Marques 《Estuaries and Coasts》2010,33(6):1327-1339
Anthropogenic activities are a disturbance factor of coastal systems and can be widely recognized as a major threat to the
health of coastal systems. However, natural events cannot be disregarded from management issues because of their significant
influence on the communities living in these areas. Based on long-term subtidal data from the Mondego Estuary (Portugal),
the effects of natural events (e.g., floods and droughts) on macrobenthic communities were compared with the anthropogenic
events. Sampling stations were grouped into characteristic zones (mouth, north arm, south arm) so the community dynamics of
each of these estuarine areas could be followed over time. Environmental assessment was performed for stations using the Benthic
Assessment Tool (BAT), and compared with the existing pressures. Human impacts persist over a number of years and gradually
reduce ecosystem health, as discussed in the European Water Framework Directive. Paradoxically, natural events cause stronger
impacts but are of a shorter duration, which allows for a faster recovery of macrobenthic communities. The study showed that
caution should be taken when developing and implementing water policies so as not to disregard the importance of the different
events (natural and human-caused) on the ecosystem health (e.g., community degradation and water quality and ecological quality
status assessment). 相似文献
18.
The contribution of rain-on-snow (ROS) events to NO3-N levels in stream water has received relatively little research attention. However, individual ROS events during January and February contributed up to 40% of annual NO3-N export from a forested catchment in south-central Ontario between 1980 and 2000, but comprised less than 10% of annual precipitation. Nitrate-N concentrations in stream water increased rapidly following ROS events, and were similar to the concentrations in incident rainfall and the accumulated snow pack, likely due to limited contact of runoff with mineral soil under snow cover and low winter biological activity. Increased NO3-N associated with ROS events resulted in substantial depressions in stream pH and alkalinity, which may delay the biological recovery from acidification. The contribution of ROS events to annual or winter NO3-N export has been generally greater in recent years, although there is a considerable year-to-year variation. As a result, ROS events contribute to inter-annual variability in stream NO3-N concentrations and will have a strong effect on apparent temporal trends. The contribution of ROS events to annual NO3-N export should be considered when assessing surface water recovery from acidification and the N-status of forests, particularly if climate change projections for winter warming result in a greater proportion of winter precipitation occurring as rain. 相似文献
19.
冰芯对于过去全球变化研究的贡献 总被引：17，自引：3，他引：14
系统地总结了冰芯在揭示过去气候环境变化、太阳活动、温室气体、火山活动、人类活动等方面研究所取得的成就,着重对一些有争议的重大问题(如Younger Dryas事件、温室气体与气候变化之间的关系、南北半球气候变化之间的关系等)进行了论述,并对其中个别问题提出了可能的解决途径.指出冰芯微生物、冰芯环境磁学将是冰芯研究的新方向. 相似文献
20.
Elastic and visco-elastic stress triggering in the South Iceland Seismic Zone due to large earthquakes since 1706 总被引：1，自引：0，他引：1
Damaging earthquakes in the South Iceland Seismic Zone (SISZ) occur fairly regularly and often as a series of events with a few days only between individual events. Tolerably reliable information on epicentre locations and mechanisms are available for 13 M ≥ 6 events between 1706 and 2000. For these events, we computed the co- and post-seismic stress fields, hereby approximating the SISZ by a mixed elastic/visco-elastic layered half-space. The horizontal shear stress and the Coulomb stress changes were analysed to detect possible trigger mechanisms, which may aid future earthquake mitigation efforts. We tested several criteria but must conclude that the start of an earthquake series in the SISZ cannot be explained by triggering through previous events. Inside an individual series, however, one may infer triggering. Our results are in contradiction with the findings in other regions of the world. The reason might be related to the fact that the SISZ is not a mature fault zone, in which old faults are re-activated if a certain stress level threshold is passed. In addition, uncertainties in the model parameters as well as the neglect of horizontal variations in the model and of possible stress transfer due to volcanic activity further complicate the evaluation of our results and need to be taken into account in future studies. 相似文献