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1.
The expression of equi-risk line derived by the authors represents the relationship between discharge capacityy 0 u and storage capacityz 0 u to keep flood frequency under a certain risk level represented by the return periodT, i.e.,z 0/z 0 u ={(y 0 u –y 0 u )/y 0 u } S , wherey 0 u andz 0 u areT-year probability peak discharge and total volume of a hydrograph. The shape parametersS is evaluated in this paper for various release rules of the storage facilities and correlations of durations and peaks of hydrographs. The expression forS is: , whereS 0 andS are the values ofS forp=0 and , andp is the exponent of a general storage-release relation,q=az' p, wherea is the storage constant, andz' andq are the volume of stored water and the corresponding release. The values ofS 0 andS are expressed in terms of the correlation coefficient of durations and peaks of inflow hydrographs.  相似文献   

2.
Proposed is a new definition of earthquake response spectra, which takes account of the number of response cycles N. The Nth largest amplitude of absolute acceleration response of a linear oscilator with natural period T and damping ratio h, which is subjected to ground motion at its base, is defined as SA(T, h, N). By defining a reduction factor η(T, h, N) as SA(T, h, N)/SA(T, h, 1), characteristics of η(T, h, N) were investigated based on 394 components of strong motion records obtained in Japan. Two practical empirical formulae to assess the reduction factor η(T, h, N) are proposed.  相似文献   

3.
A layeredP- andS-wave velocity model is obtained for the Friuli seismic area using the arrival time data ofP- andS-waves from local earthquakes. A damped least-squares method is applied in the inversion.The data used are 994P-wave arrival times for 177 events which have epicenters in the region covered by the Friuli seismic network operated by Osservatorio Geofisico sperimentale (OGS) di Trieste, which are jointly inverted for the earthquake hypocenters andP-wave velocity model. TheS-wave velocity model is estimated on the basis of 978S-wave arrival times and the hypocenters obtained from theP-wave arrival time inversion. We also applied an approach thatP- andS-wave arrival time data are jointly used in the inversion (Roecker, 1982). The results show thatS-wave velocity structures obtained from the two methods are quite consistent, butP-wave velocity structures have obvious differences. This is apparent becauseP-waves are more sensitive to the hypocentral location thanS-waves, and the reading errors ofS-wave arrival times, which are much larger than those ofP-waves, bring large location errors in the joint inversion ofP- andS-wave arrival time. The synthetic data tests indicated that when the reading errors ofS-wave arrivals are larger than four times that ofP-wave arrivals, the method proposed in this paper seems more valid thanP- andS-wave data joint inversion. Most of the relocated events occurred in the depth range between 7 and 11 km, just above the biggest jump in velocity. This jump might be related to the detachment line hypothesized byCarulli et al. (1982). From the invertedP- andS-wave velocities, we obtain an average value 1.82 forV p /V s in the first 16 km depth.  相似文献   

4.
Summary Evidence is adduced indicating that geomagnetic disturbance at Huancayo isnormal, that is, comparable with that shown elsewhere in similar latitudes —as contrasted with the remarkable Huancayoabnormality, in the horizontal magnetic force, of the quiet-day solar and lunar daily variations, and in theS q augmentation (solar flare effect). the normality of magnetic disturbance at Huancayo is manifested by the disturbance daily variationS D, and by the storm-effectD st and its associated changes of daily mean (D m) and the non-cyclic variation; it is not stated whether or not the irregular part,D i, is normal. The normality ofD st seems natural according to theChapman-Ferraro theory of magnetic storms, but the normality ofS D is less easy to explain.Prof.Sydney Chapman, Research Associate, California Institute of Technology, under Signal Corps Project No. 24-172 B; on leave (from April 1950 to March 1951) from Oxford University, Queen's College,Oxford, England.  相似文献   

5.
The research of the information dimension (D 1) in an active fault zone considers the contribution of each seismic event to information and reflects the characteristics of the temporal and spatial distributions of earthquakes from a new point of view, avoiding some short-comings of the research about the capacity dimension (D 0). The results of calculation show that the information dimension of the temporal distribution in Xianshuihe active fault zone before Luhuo large earthquake isD 1=0.1051. It is a consult creterion of large earthquakes in future in the fault zone. The information dimensions of the temporal distribution of the earthquakes in Anninghe active fault zone are respectivelyD 1(t N)=0.1363 (for the north section) andD 1(t S)=0.06710 (for the south section). The information dimensions of the spatial distribution are respectivelyD 1(K N)=1.053 (for the north section) andD 1(K S)=0.7758 (for the south section). The north section and the south section belong to two self-similar systems with different information dimensions respectively. The extent of the self-organization of seismic activity in the south section is higher than that in the north section. This is helpful for us to judge the major dangerous section in the key region of the seismic monitoring. The research about the information dimension of the temporal and the spatial distributions of earthquakes is significant for the exploration of active fault zones and seismic prediction. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 372–379, 1991. This paper is sponsored by the Chinese Joint Seismological Science Foundation. The English version is improved by Zhenwen An.  相似文献   

6.
Geomagnetic solar and lunar daily variationsS andL, at Alibag, India are derived, by the well-known Chapman-Miller method, from the series of homogeneous mean hourly magnetic data of the years 1932 to 1972. The data for all the three elements — declinationD and horizontal and vertical intensitiesH andZ — are analysed, by dividing the data suitably for a study of the seasonal variations, the effect of the changes in the solar and magnetic activities onS andL, the oceanic dynamo contribution toL, and their interactions with each other. The main results are as follows.
  1. ForS the daily pattern and its seasonal progression conform to the type expected from a northern-hemisphere station. On the other hand, the amplitudes of all the four harmonics ofL systematically have higher values in winter, and inD andZ the harmonics show large phase differences between summer and winter. The pattern ofL in winter suggests that the lunar current system consists of a single set of vortices in the summer hemisphere rather than the conventional vortices, one set in each of the hemispheres.
  2. Solar-cycle modulation on the solar ranges as well as on the amplitudes of the first three harmonics ofS is greater than that expected solely from the increase in E-region conductivity, whereas the corresponding modulation onL is comparable to that on the E-region conductivity.
  3. With increasing magnetic activity the first harmonic ofS shows an increase, and the first three harmonics ofL indicate a general decrease, in amplitude.
  4. Of the variability inS 96%, but inL only 32%, is found to be accounted for by the combined effect of the variations in the solar and magnetic activities.
  相似文献   

7.
Roger Moussa 《水文研究》2008,22(3):395-419
  相似文献   

8.
Summary Solar and lunar geomagnetic tides inH at Alibag have been determined by spectral analysis of discrete Fourier transforms following the method of Black and the well-known Chapman-Miller method. The seasonal variation inL 2(H) is opposite to that inL 2(D) with maximum in thed season and minimum in thej season. In bothH andD the enhancement due to sunspot activity is larger in lunar tide than in solar tide. Surprisingly, the enhancement due to magnetic activity is greater inL 2(H) than inS 1(H), while the contrary is true for declination. It is inferred that there is a local time component of the storm time variation contrary to the view expressed by Green and Malin. The enhancements in amplitudesL 2 andS 1 inH andD, due to sunspot activity and due to magnetic activity, have been separated. The results show that the amplitude at zero sunspot number increases with magnetic activity in all the four parameters, while the enhancement due to sunspot activity at different levels of magnetic activity decreases with increase ofK p. But if bothK p andR are increasing, whenK p increases enhancement due toR decreases and whenR increases enhancement due toK p decreases.  相似文献   

9.
Hydrologic analysis of urban drainage networks often encounters a number of issues, including data acquisition and preparation for modelling, which can be costly and time‐consuming processes. Moreover, it can get more challenging with missing data and complex loops inside networks. In this article, Gibbs’ model is applied to urban drainage networks to investigate the possibility of replacing an actual existing urban drainage network in terms of the shape and peak flow of the hydrographs at the outlet. The characteristic network configuration is given as a value of a parameter β of Gibbs’ model. Instead of the actual network, stochastic networks from Monte‐Carlo simulation are utilized to obtain a synthetic width function from the generated networks, and runoff hydrographs are estimated based on it. The results show that the synthetic width function and the resulting hydrographs obtained from the networks simulated by Gibbs’ model are close to those from the actual network. The result also shows that even the behaviour of a looped network can be approximated by equivalent dendritic networks generated by Gibbs’ model. The applicability of a stochastic network model in urban catchment implies a complement to modelling approaches in case of data unavailability. Moreover, the network property (β) is utilized not only to estimate the discharge hydrograph of a catchment but also as a key link to evaluate the effect from rainstorm movement in urban catchments. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

10.
Abstract

Large errors in peak discharge estimates at catchment scales can be ascribed to errors in the estimation of catchment response time. The time parameters most frequently used to express catchment response time are the time of concentration (TC), lag time (TL) and time to peak (TP). This paper presents a review of the time parameter estimation methods used internationally, with selected comparisons in medium and large catchments in the C5 secondary drainage region in South Africa. The comparison of different time parameter estimation methods with recommended methods used in South Africa confirmed that the application of empirical methods, with no local correction factors, beyond their original developmental regions, must be avoided. The TC is recognized as the most frequently used time parameter, followed by TL. In acknowledging this, as well as the basic assumptions of the approximations TL = 0.6TC and TC ≈ TP, along with the similarity between the definitions of the TP and the conceptual TC, it was evident that the latter two time parameters should be further investigated to develop an alternative approach to estimate representative response times that result in improved estimates of peak discharge at these catchment scales.
Editor Z.W. Kundzewicz; Associate editor Qiang Zhang  相似文献   

11.
Summary The author proposes a new technique of magnetic interpretation in the case of a two-dimensional model, whereby six analytical expressions are deduced and computed forDH, DZ, PHB, PZB, AHB andAZB. These expressions denote the induced part of magnetic anomaly inH component, the induced part of anomaly inZ component, the permanent magnetization part ofH anomaly, the permanent magnetization part ofZ anomaly, the sum (DH+PHB), and the sum (DZ+PZB), respectively. The use of a series of these six curves taken together instead of the single profile curve, will improve the existing method of magnetic interpretation, reduce the uncertainties of the inverse problem, and provide a valuable tool for paleomagnetic studies of in situ older rocks commonly found in equatorial Africa. The resulting advantages outweigh the apparent increase in computation. This technique was applied to a field profile obtained across a subsurface dolerite vein, and the results agree with the theoretical predictions outlined.  相似文献   

12.
Rainfall interception loss plays an important role in ecohydrological processes in dryland shrub ecosystems, but its drivers still remain poorly understood. In this study, a statistical model was developed to simulate interception loss based on the mass balance measurements arising from the partitioning of rainfall in 2 dominant xerophytic shrub (Hippophae rhamnoides and Spiraea pubescens) communities in the Loess Plateau. We measured throughfall and stemflow in the field under natural rainfall, calculated the canopy storage capacity in the laboratory, and identified key factors controlling these components for the 2 shrubs. We quantified and scaled up the stemflow and the canopy storage capacity measurements from the branches and/or leaves to stand level. The average interception loss, throughfall, and stemflow fluxes account for 24.9%, 72.2%, and 2.9% of the gross rainfall for H. rhamnoides, and 19.2%, 70.7%, and 10.1% for S. pubescens, respectively. Throughfall increased with increasing rainfall for both shrubs; however, it was only correlated with the leaf area index for S. pubescens. For stemflow measured from individual branches, we found that the rainfall amount and basal diameter are the best predictors for H. rhamnoides, whereas rainfall amount and branch biomass appear to be the best predictors for S. pubescens. At the stand level, stemflow production is affected by the rainfall amount for H. rhamnoides, and it is affected by both the rainfall amount and the leaf area index for S. pubescens. The canopy storage capacity of H. rhamnoides (1.07–1.28 mm) was larger than S. pubescens (0.88–1.07 mm), and it is mainly determined by the branches and stems of H. rhamnoides and the leaves of S. pubescens. The differences in interception loss between the 2 shrub stands are mainly attributed to different canopy structures that induced differences in stemflow production and canopy storage. We evaluated the effects of canopy structure on rainfall interception loss, and our developed model provides a better understanding of the effects of the canopy structure on the water cycles in dryland shrub ecosystems.  相似文献   

13.
Summary The present paper contains studies of the nocturnal radiation at some Indian Stations (Madras, Waltair, Nagpur, New Delhi and Poona) with the help of the Ångström compensation Pyrgeometer. The technique of measurement is also described briefly. A study of the mean monthly variation of sky radiation during clear as well as all nights has been discussed. A comparitive study of mean monthly values of sky and other nocturnal radiation components at these stations is also presented. Ångström, [4]2) expressed the dependence of sky radiationS—on water vapour pressuree (mm of mercury) at the earth's surface and air temperatureT (degrees absolute), near the instrument to be given byS=T 4 (0.75–0.32×10–0.069e ) cal/cm2/min. According to this semi-empirical relationship, the calculated values of sky radiation for clear nights are smaller than the observed values of sky radiation at all the above stations. It is for this reason the authors obtained a new formula with different constants using nine years observed data at all the stations. To investigate the value of the constant, the mean annual observations presented for nine years from clear skies were analysed for correlations betweenB (black body radiation) versesS (sky radiation),N (net radiation) andE (absolute error) and obtained a good correlation co-efficients 0.90, 1 and 0.98 respectively. The new suggested formula isS=T 4 (0.88–0.32×10–0.069e ) cal/cm2/min, 267° A<T<313° A. It is also verified using with observed data of different years of the stations. The agreement between the computed values with the new formula of sky radiation and observed sky radiation is found to be good.  相似文献   

14.
We theoretically study the scattering ofP, SV andSH waves by a zonal distribution of cracks, which simulates a fault fracture zone. An investigation is conducted how the geometrical properties of the crack distribution and the frictional characteristics of the crack surface are reflected in the attenuation and dispersion of incident waves, as well as in the amplitudes of the transmitted and reflected waves from the zone. If the crack distribution within the fault zone changes temporally during the preparation process of the expected earthquake, it will be important for earthquake prediction to monitor it, utilizing the scattering-induced wave phenomena.We consider the two-dimensional problem. Aligned cracks with the same length are assumed to be randomly distributed in a zone with a finite width, on which elastic waves are assumed to be incident. The distribution of cracks is assumed to be homogeneous and sparse. The crack surface is assumed to be stress-free, or to undergo viscous friction; the latter case simulates fluid-filled cracks. The opening displacement of the crack is assumed to be negligibly small. The idea of the mean wave formalism is employed in the analysis, and Foldy's approximation is assumed.When the crack surface is stress-free, it is commonly observed for every wave mode (P, SV andSH) that the attenuation coefficientQ –1 peaks aroundka1, the phase velocity is almost independent ofk in the rangeka<1 and it increases monotonically withk in the rangeka>1, wherek is the intrinsicS wavenumber anda is the half length of the crack. The effect of the friction is to shift the peak ofQ –1 and the corner of the phase velocity curve to the low wavenumber range. The high wavenumber asymptote ofQ –1 is proportional tok –1 independently of model parameters and the wave modes. If the seismological observation thatQ –1 ofS waves has a peak at around 0.5 Hz in the earth's crust is combined with our results, the upper limit of crack size within the crust is estimated about 4 km. The information regarding the transmitted and reflected waves, such as the high wavenumber limit of the amplitude of the transmitted wave etc., allows estimation of the strength of the friction.  相似文献   

15.
Near-field records of two strong aftershocks with magnitudeM S=6.7 andM S=6.3 in the Lancang-Gengma earthquakes sequence, Yunnan Province, November 1988, are used to calculate the response spectrum. The instruments, site conditions and the methods for computing are also illustrated in this paper. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 338–343, 1991. This project is supported by The Chinese Joint Seismological Science Foundation, SSB and the West Yunnan Earthquake Prediction Test Field, Yunnan Seismological Bureau.  相似文献   

16.
In the framework of the revision of Part 1 of Eurocode 8, this study aims at developing new empirical correlations to compute peak values of ground velocity (PGV) and displacement (PGD) as a function of elastic spectral ordinates for design. At variance with the expressions for PGV and PGD currently adopted in the Eurocode 8, based solely on the peak ground acceleration (PGA), in this paper reference is made to spectral ordinates of the short and intermediate period range, namely Ss, which is the constant acceleration spectral ordinate, and S1, which is the spectral ordinate at 1 s. On the one hand, a relationship between PGV and the product (Ss?S1) was found based on the regression analysis on a high‐quality strong‐motion dataset. On the other hand, the PGD was estimated by extrapolating to long periods the constant displacement branch of the elastic response spectrum, introducing a correlation between the corner period TD and S1. For this purpose, results of a long period probabilistic seismic hazard assessment study for Italy, encompassing low to high seismicity areas, were considered. Furthermore, verification of the proposed relationship against strong‐motion records was carried out, and differences justified in terms of the concept of uniform hazard spectrum.  相似文献   

17.
The aging of the hydrothermal plume over the Endeavour segment of the Juan de Fuca Ridge was estimated by measuring the222Rn3He ratio in the plume as it dispersed. Despite uncertainties in the source function of hydrothermal input, it wa determined that the relative sequence of removal from the plume isH2 > Δc >222Rn>CH4 Mn, whereΔc is a measure of particle concentration and the mean life of222Rn is 5.5 days. H2 is removed from the plume within hours of input while Mn is not removed within the two-week timescale of the radon-helium clock.Entrainment of bottom water within the buoyant plume may introduce additional chemical signatures into the spreading effluent layer over that which would be introduced by hydrothermal discharge alone. This is particularly significant for those chemical species which are not greatly enriched in the vent fluids relative to bottom water concentration and which display a nutrient-like profile in the deep ocean. Thus we found that significant fractions of the Si and226Ra anomalies in the plume were not of hydrothermal origin but were derived from entrained bottom water which has a higher concentration of these elements than ambient water at plume height.  相似文献   

18.
Summary Analytic expressions for the far-field displacement both in the time and the frequency domains are obtained for the kinematic earthquake model of a rupture which nucleates at a point, grows in the form of a rectangle and stops at a later time.The spectra ofS andP waves are analyzed with the object of determining fault dimensions from the corner frequencies. The approach by which the solution of the present problem is obtained can be extended to get closed form solutions to the problem of rupture front expanding in the form of a polygon and terminating over a fault area which has the form of another polygon.  相似文献   

19.
Previous genetic studies on perch (Perca fluviatilis L.) in northern and southern regions of Europe have shown low heterozygosity. No such investigation has been conducted in the central part of Europe. The genetic variability ofP. fluviatilis in four Swiss lakes (Lake Constance, Lake Zürich, Lake Geneva and Lake Maggiore) was investigated. These four lakes belong to three different drainage systems (Rhine, Rhone and Po) without connections. A total of 136 fish were analysed electrophoretically. Only one locus (SOD *) was highly polymorphic in Lake Constance among the 27 loci studied. The expected heterozygosities for each population and for the total population were higher than in the previous studies but low (H S= 0.38–2.7%;H T=1.22%) and Nei's genetic distances were small (0.000–0.003). However, the jack-knifed mean of the Wright'sF STwas calculated as 0.142, which indicates modest genetic differentiation among the perch populations in Switzerland, due to the differentiated population in Lake Constance.  相似文献   

20.
Summary The global distributions of the annual and seasonal means of the diurnal (S 1) and semidiurnal (S 2) surface pressure oscillations are investigated by spherical harmonic analysis. The main waves are,S 1 1 (with wave number 1) forS 1 andS 2 2 forS 2.S 1 1 is much less predominant among the waves ofS 1 thanS 2 2 among those ofS 2. As in the case of the lunar semidiurnal barometric tideL 2 the pressure maxima occur earlier in the Southern than in the Northern Hemisphere. In the case ofS 2 the standing waveS 2 0 and the waveS 2 3 are also of interest besidesS 2 2. Although the present analysis extends only from 60°N to 60°S, whileS 2 0 is largest at polar latitudes, its results show thatS 2 0 should be smaller at high southerly than at high northerly latitudes, as has been observed. Thus this observed asymmetrical distribution ofS 2 0 may be due to causes outside the polar regions rather than to their geographical differences. The best approximation to the observed distribution ofS 2 0 is obtained by including a mode representing an oscillation independent of longitude and latitude indicating a small semidiurnal variation of the mean global surface presure, which is an unlikely result on physical grounds.The seasonal variation ofS 1 1 expressed in percent of the annual mean is smaller than that ofS 2 2, and both are less than the unexplained seasonal variation ofL 2 2.The main wavesS 1 1 andS 2 2 are expressed not only by associated Legendre functions, but also by Hough functions.National Center for Atmospheric Research, Boulder, Colorado, U.S.A., sponsored by the National Science Foundation.  相似文献   

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