共查询到20条相似文献，搜索用时 312 毫秒
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I. Becchi E. Caporali L. Castellani E. Palmisano F. Castelli 《Surveys in Geophysics》1995,16(2):227-252
In the study of flash-flood occurrence in small catchments the lack of flow measurements is often one of the main limiting factors. Prior to estimating the forecasting potentialities and techniques for such events, an accurate reconstruction of past event flood dynamics is first required. This issue is here addressed by analyzing, with the use of a distributed hydrological model, the hydrometeorological conditions in which a severe flash-flood occurred, on October 1992, on a 48 square kilometers catchment in the Arno basin. Such an event was caused by the persistence of intense convective clusters on the background of widespread rain bands of frontal origin. The distributed hydrological model here adopted is devoted to simulate the evolution and the variability of the primary processes involved in the runoff cycle. Together with the hydrological model structure, other particular aspects of the event reconstruction procedure are discussed: the managing and processing of the information coming from different sensors, with different temporal and spatial resolutions; the identification of local precipitation dynamics (frontal or convective) within small areas of integrated radar and rain gauges data fields; the interpolation of rain gauge data on the basis of the radar-estimated spatial correlation. The results of the distributed modeling, concerning the estimate of the flood wave at various sites, are compared with analogous results obtained with simpler lumped models. 相似文献
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我国南方碳酸盐岩广泛分布,具有巨大的油气资源潜力和勘探前景.全国油气资源战略选区调查与评价项目选择我国典型南方海相碳酸盐岩裸露区开展地震勘探技术攻关.针对该区地表灰岩普遍出露、激发弹性波能量转换少、散射噪音干扰严重等勘探难点,研究和应用了“宽线+折线”地震采集技术和与其配套的拟三维地震处理技术,能较好地压制噪音,提高剖面信噪比,在主要目的层得到了较好的成像效果,桂中1井钻探结果与地震勘探解释成果吻合较好,检验了该方法用于南方碳酸盐岩地区勘探的有效性. 相似文献
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A main task of weather services is the issuing of warnings for potentially harmful weather events. Automated warning guidances can be derived, e.g., from statistical post-processing of numerical weather prediction using meteorological observations. These statistical methods commonly estimate the probability of an event (e.g. precipitation) occurring at a fixed location (a point probability). However, there are no operationally applicable techniques for estimating the probability of precipitation occurring anywhere in a geographical region (an area probability). We present an approach to the estimation of area probabilities for the occurrence of precipitation exceeding given thresholds. This approach is based on a spatial stochastic model for precipitation cells and precipitation amounts. The basic modeling component is a non-stationary germ-grain model with circular grains for the representation of precipitation cells. Then, we assign a randomly scaled response function to each precipitation cell and sum these functions up to obtain precipitation amounts. We derive formulas for expectations and variances of point precipitation amounts and use these formulas to compute further model characteristics based on available sequences of point probabilities. Area probabilities for arbitrary areas and thresholds can be estimated by repeated Monte Carlo simulation of the fitted precipitation model. Finally, we verify the proposed model by comparing the generated area probabilities with independent rain gauge adjusted radar data. The novelty of the presented approach is that, for the first time, a widely applicable estimation of area probabilities is possible, which is based solely on predicted point probabilities (i.e., neither precipitation observations nor further input of the forecaster are necessary). Therefore, this method can be applied for operational weather predictions. 相似文献
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古地震资料要在地震中长期预报和地震危险性评估中发挥更重要的作用,关键在于减小古地震研究中的不确定性,古地震发生年代的确定是最大限度减小不确定性的关键因素之一。要得到尽可能接近真实的古地震事件年代,除正确地选择测年方法外,正确的采样方法和事件年代确定技术尤为关键。在几种主要测年技术中,优先采集碳十四(14C)测年样品、释光样品采集搬运过程有充分"退火"条件的物质、铍十(10Be)样品应采集各种干扰因素较少的样品、依据构造运动属性选择适宜的采样位置、用序列样品限制事件年代等,是正确采集测定事件年代样品的技术要点;用地层年代限制的事件发生年代宜用区间值、有多个可信样品年龄值时应用年轻样品的年代数据,是确定单一地点事件发生年代的基本原则;而包括逐次限定法、Z统计法、年龄分布曲线重叠法、事件窗法、年龄分布曲线权重重叠法在内的时间对比法,以及空间对比法是断层或断层段多个测年地点事件年代估计的主要分析方法。 相似文献
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KLAS SANDSTR
M 《水文研究》1996,10(5):703-720
There is a critical lack of knowledge regarding the dynamics of streamflow generation in the semi-arid tropics, particularly in Africa. In this project runoff mechanisms in forested and non-forested degraded catchments in northern Tanzania were studied using combined hydrometrical and hydrochemical methods. Following the hydrochemical identification of several flowpaths contributing to runoff, hydrograph separation by an end-member model based on K and Ca was undertaken. Results from the forested catchment indicate that stormflow was dominated by event water (about 75%), via overland flow and throughflow. The proportion of pre-event water (groundwater) displaced into the stream by a suggested riparian groundwater ridge mechanism varied, depending on the rainfall characteristics. In the non-forested, degraded catchment, nearly all stormflow was event water, and groundwater discharge was unaffected by rainfall. It is suggested that macropore flow is pivotal to the transmission of rainfall to runoff via throughflow, particularly in semi-arid tropical areas. 相似文献
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运用经验格林函数法模拟了2008年5月12日汶川8.0级大地震的近场强地面运动.拟合过程中,首先参考其他学者反演结果给出的滑动量分布的特征,确定强震动生成区的大致范围;然后利用Somerville等(1999)提出的地震矩与凹凸体面积间的经验关系式确定强震动生成区(SMGA)细小划分的初值,继而利用遗传优化算法确定以上两者的最优值及其他震源参数.数值模拟波形同实际地震观测记录在时间域和频率域分别进行了比较,结果显示,在所选取的18个观测台中,多数台站的数值模拟结果同实际观测结果符合得很好,特别是大于1 Hz的高频部分.我们发现断层面上有5个强震动生成区,其中两个的位置与其他学者反演的滑动量集中分布区相一致,但强震动生成区规模和上升时间比Somerville等(1999)获得的定标率外延的估计值要小. 相似文献
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K. Koch 《Pure and Applied Geophysics》2002,159(4):759-778
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This paper investigates the sensitivity of the predicted seismic response of buildings in a PWR nuclear power station to the potential changes in the techniques and methods of interpreting soil data that have occurred over the last decade. The investigation is based on the soil-structure interaction (SSI) response of a typical PWR reactor building on a soft site during a seismic event. The current techniques and methods of interpretation of soils data tend to lead to a stiffer site with lower soil material damping than the earlier techniques. This leads to an increase in the SSI natural frequencies of typical buildings and an increase in its seismic response. This increase in the seismic response could put into question any seismic design based on seismic loads derived using the previously accepted generic soil data. The paper concludes with a recommendation for further consideration of the proposed departure from the previously accepted soil data. 相似文献
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One year of instantaneous suspended sediment concentration, C, and instantaneous discharge, Q, data collected at Ngarradj downstream of the Jabiluka mine site indicate that the use of a simple C–Q rating curve is not a reliable method for estimating suspended sediment loads from the Ngarradj catchment. The C–Q data are not only complicated by hysteresis effects within the rising and falling stages of individual events, but also by variable depletion of available suspended sediment through multipeaked runoff events. Parameter values were fitted to an event‐based suspended sediment load–Q relationship as an alternative to the C–Q relationship. Total suspended sediment load and Q data for 10 observed events in the Ngarradj stream catchment were used to fit parameter values to a suspended sediment load–Q relationship, using (a) log–log regression and (b) iterative parameter fitting techniques. A more reliable and statistically significant prediction of suspended sediment load from the Ngarradj catchment is obtained using an event‐based suspended sediment load–Q relationship. Fitting parameters to the event‐based suspended sediment load–Q relationship using iterative techniques better predicts long‐term suspended sediment loads compared with log–log regression techniques. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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José M. Angulo Francisco J. Esquivel 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1187-1206
Different approaches and tools have been adopted for the analysis and characterization of regional seismicity based on spatio–temporal series of event occurrences. Two main aspects of interest in this context concern scaling properties and dimensional interaction. This paper is focused on the statistical use of information-theoretic concepts and measures in the analysis of structural complexity of seismic distributional patterns. First, contextual significance is motivated, and preliminary elements related to informational entropy, complexity and multifractal analysis are introduced. Next, several technical and methodological extensions are proposed. Specifically, limiting behaviour of some complexity measures in connection with generalized dimensions is established, justifying a concept of multifractal complexity. Under scaling behaviour, a mutual-information-related dependence coefficient for assessing spatio–temporal interaction is defined in terms of generalized dimensions. Also, an alternative form of generalized dimensions based on Tsallis entropy convergence rates is formulated. Further, possible incorporation of effects, such as earthquake magnitude, is achieved in terms of weighted box-counting distributions. Different aspects in relation to the above elements are analyzed and illustrated using two well-known series of seismic event data of an underlying different nature, occurred in the areas of Agrón (Granada, Spain) and El Hierro (Canary Islands, Spain). Finally, various related directions for continuing research are indicated. 相似文献
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This paper describes the application of a methodology for the evaluation of debris-flow risk in alluvial fans by incorporating numerical simulations with Geographical Information Systems to identify potential debris-flow hazard areas. The methodology was applied to a small catchment located in the north-eastern part of Sicily, Italy where an extreme debris flow event occurred in October 2007. The adopted approach integrates a slope stability model that identifies the areas of potential shallow landslides under different meteorological conditions using a two-dimensional finite-element model based on the De Saint Venant equation for the debris-flow propagation. The mechanical properties of the debris were defined using both laboratory and in situ test results. The risk classification of the area under study was derived using total hydrodynamic force per unit width (impact pressure) as an indicator for event intensity. Based on the simulation results, a potential risk zone was identified and mapped. 相似文献
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Chih-Hsiang Ho Eugene I Smith Daniel L Feuerbach Terry R Naumann 《Bulletin of Volcanology》1991,54(1):50-56
Investigations are currently underway to evaluate the impact of potentially adverse conditions (e.g. volcanism, faulting, seismicity) on the waste-isolation capability of the proposed nuclear waste repository at Yucca Mountain, Nevada, USA. This paper is the first in a series that will examine the probability of disruption of the Yucca Mountain site by volcanic eruption. In it, we discuss three estimating techniques for determining the recurrence rate of volcanic eruption (), an important parameter in the Poisson probability model. The first method is based on the number of events occurring over a certain observation period, the second is based on repose times, and the final is based on magma volume. All three require knowledge of the total number of eruptions in the Yucca Mountain area during the observation period (E). Following this discussion we then propose an estimate of E which takes into account the possibility of polygenetic and polycyclic volcanism at all the volcanic centers near the Yucca Mountain site.Paper financed by the Nuclear Waste Project Office, State of Nevada, USA 相似文献
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Non-indigenous species (NIS) are a growing problem globally and, in the sea, aquaculture activities are critical vectors for their introduction. Aquaculture introduces NIS, intentionally or unintentionally, and can provide substratum for the establishment of other NIS. Little is known about the co-occurrence of NIS over long periods and we document the coexistence over decades of a farmed NIS (a mussel) with an accidently introduced species (an ascidian). Both are widespread and cause serious fouling problems worldwide. We found partial habitat segregation across depth and the position of rafts within the studied farm, which suggests competitive exclusion of the mussel in dark, sheltered areas and physiological exclusion of the ascidian elsewhere. Both species exhibit massive self-recruitment, with negative effects on the industry, but critically the introduction of NIS through aquaculture facilities also has strong detrimental effects on the natural environment. 相似文献
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—?Microseismic monitoring systems are generally installed in areas of induced seismicity caused by human activity. Induced seismicity results from changes in the state of stress which may occur as a result of excavation within the rock mass in mining (i.e., rockbursts), and changes in hydrostatic pressures and rock temperatures (e.g., during fluid injection or extraction) in oil exploitation, dam construction or fluid disposal. Microseismic monitoring systems determine event locations and important source parameters such as attenuation, seismic moment, source radius, static stress drop, peak particle velocity and seismic energy. An essential part of the operation of a microseismic monitoring system is the reliable detection of microseismic events. In the absence of reliable, automated picking techniques, operators rely upon manual picking. This is time-consuming, costly and, in the presence of background noise, very prone to error. The techniques described in this paper not only permit the reliable identification of events in cluttered signal environments they have also enabled the authors to develop reliable automated event picking procedures. This opens the way to use microseismic monitoring as a cost-effective production/operations procedure. It has been the experience of the authors that in certain noisy environments, the seismic monitoring system may trigger on and subsequently acquire substantial quantities of erroneous data, due to the high energy content of the ambient noise. Digital filtering techniques need to be applied on the microseismic data so that the ambient noise is removed and event detection simplified. The monitoring of seismic acoustic emissions is a continuous, real-time process and it is desirable to implement digital filters which can also be designed in the time domain and in real-time such as the Kalman Filter. This paper presents a real-time Kalman Filter which removes the statistically describable background noise from the recorded seismic traces. 相似文献
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For the purpose of verifying compliance with the CTBT seismic monitoring is one of the four techniques used by the IDC. In order to improve the accuracy of the automatic and the reviewed bulletin epicenter locations the IDC uses SASC for the IMS seismic stations. SASC determination is a straightforward calculation done by comparing for selected events the azimuth and slowness from the waveform processing using array techniques to the theoretical values based on the event locations and the velocity model.The main problem, however, is to build a set of reference events, whose locations are accurate enough and not based on information from the stations to be calibrated. A reference event list assumed to meet this requirement is the Gamma bulletin, which was collected since 1993 and was compiled in the framework of the GSETT-3. In this work calculation of SASC for regional to teleseismic distances (up to 30 degrees) was performed for 11 IMS primary arrays. The calculation was done using Pg, Pn, P, Sg, Sn, and S phases based on the detection list obtained from the pIDC and the Gamma bulletin for 6 years (1993–1999). The number of Gamma events varies from several hundreds for some arrays (BRAR) to several tens of thousands for others (i.e. ARCES, ILAR). Due to the fact that the Gamma bulletin is purely voluntary, the coverage is non-uniform both in time and in space and the location accuracy is non-uniform. This drawback can be overcome by encouraging signatory states to submit quality Gamma bulletin data to the IDC. The work presented here can be used as a routine procedure for improving IMS array performance, especially at regional distances. 相似文献
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对公元前179年(汉文帝前元元年)"齐楚地震"的基本参数一直有不同认识,属于疑难历史地震。在吸收西汉政区研究成果的基础上,深入分析了地震史料隐含的约束条件,对这次地震震中位置进行了考证。提出了以齐楚边界和国都连线为基点,结合史料给出的有关约束条件,综合确定震中位置的技术方案。同时,依据地震地质调查成果,从发震构造角度论证了震中位置的合理性。1)鉴于西汉时期政权更迭频繁,通过追踪西汉初期(尤其是汉文帝前元元年前后)齐、楚政区变化情况,尽力复原当时的行政区划和齐楚两国边界分布。2)认真分析史料记载的"齐楚地震,二十九山同日崩,大水溃出"所指示的地区范围,对比历史上其他震例造成的破坏现象的空间分布以及破坏程度,为震中位置和震级确定提供重要约束条件。经文献考证认为,这次地震可定为公元前179年6月6日平邑南(35.2°N,117.6°E)7级地震。3)结合卫星影像判读和野外地震地质调查资料,分析研究了"齐楚地震"所在地区的地质构造特点和活动断裂发育情况。在排除该地震事件属于郯庐断裂带地震事件后,通过对比分析郯庐断裂带西侧发育的各条NW向断裂的构造地貌以及剖面表现,认为苍尼断裂可能是"齐楚地震"的发震断裂。在震中附近,苍尼断裂控制着白彦断陷盆地的发育,也是断层地貌最为清楚的地方,断错的地层最新,断层运动量也最大。 相似文献
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Ralf Fritschen 《Pure and Applied Geophysics》2010,167(1-2):77-89
Coal mining in the Saar mine, Germany, is accompanied by mining-induced seismic events. Strong events occur only in certain areas of the mine, other areas exhibit almost no seismicity. Shear events occur simultaneously to non-shear events. The shear events occur in different depths but their epicenters do concentrate in bands. The strike of the bands coincides with the strike of larger regional faults in the area. The seismic events of the Saar mine show some characteristics which distinguish them from seismic events observed in other German coalfields. The Gutenberg–Richter relation, for example, does not hold for these events. Furthermore, radiated seismic energy and extracted coal volume are not correlated. In the Primsmulde field a strong seismic event was observed even before mining in that region started. The event was triggered just by driving roadways into the field. The shear events cannot be explained by the mining process alone. They are presumably induced in certain regions (bands) under tectonic load by an interaction of mining-induced and tectonic stresses. In February 2008, extraction in the Primsmulde field induced a seismic event of magnitude 4, which led to surface vibrations reaching 93 mm/s. After this event, the Primsmulde field had to be abandoned. Future extraction of the Saar mine will be restricted to some small areas not intersected by the event bands found in the Dilsburg Ost and Primsmulde fields. The Saar mine will close in 2011. 相似文献
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