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1.
Empirical attenuation relationship for Arias Intensity   总被引：1，自引：0，他引：1  
Arias Intensity is a ground motion parameter that captures the potential destructiveness of an earthquake as the integral of the square of the acceleration–time history. It correlates well with several commonly used demand measures of structural performance, liquefaction, and seismic slope stability. A new empirical relationship is developed to estimate Arias Intensity as a function of magnitude, distance, fault mechanism, and site category based on 1208 recorded ground motion data from 75 earthquakes in active plate‐margins. Its functional form is derived from the point‐source model, and the coefficients are determined through non‐linear regression analyses using a random‐effects model. The results show that for large magnitude earthquakes (M > 7) Arias Intensity was significantly overestimated by previous relationships while it was underestimated for smaller magnitude events (M ? 6). The average horizontal Arias Intensity is not significantly affected by forward rupture directivity in the near‐fault region. The aleatory variability associated with Arias Intensity is larger than that of most other ground motion parameters such as spectral acceleration. However, it may be useful in assessing the potential seismic performance of stiff engineering systems whose response is dominated by the short‐period characteristics of ground motions. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

2.
The Local-Magnitude scale actually in use at Vesuvius Observatory is basedon the measure of seismogram coda duration, and calibrated with data fromIrpinia aftershocks. A recent study on local seismic attenuation at Mt.Vesuvius reveals coda shapes highly different from those from Irpiniaaftershocks, and a very low quality factor, if compared to the average Qof the region, indicating the necessity of the revision of the Magnitudescale, in order to better compare the seismic energy associated to the localseismicity of Mt. Vesuvius to that of other active volcanoes. Being theseismic attenuation parameters known in the area, we could correct theseismic amplitudes for the path effect to obtain precise estimates of theamplitude level of the displacement spectrum. Hence we estimated theMoment-Magnitude, M W, for a set of well recorded micro-earthquakes.To use the Richter formulaM L =log10 A max –log A0(R)we estimated the log Amplitude-Distance correction curve, - log A0(R),numerically synthesizing an S-wave-packet and letting it propagate in aearth medium with the same attenuation properties of those measured at Mt.Vesuvius. Then we synthesized the Wood-Anderson equivalent seismogram forthe same data set and used the distance correction in order to calculate theWood-Anderson Magnitude.This Magnitude scale was normalized in order to fit the Richter formulavalid for Southern California at a distance of 10 km, and resultsto be M WA =log A + 1.34log(R) –1.10. The comparison of the Wood-Anderson scale with the Duration-Magnitude scalein routine use at Vesuvius Observatory indicates that care must be takenwhen the estimate of the Duration-Magnitude is carried out for smallearthquakes recorded at a site characterized by a high level of seismicnoise.  相似文献   

3.
Statistical methods are available which predict the maximum response of simple oscillators given the peak acceleration (Ap), peak velocity (Vp) or peak displacement (Dp) of seismic ground motions. An alternative parameter, namely an ordinate (or ordinates) of the Fourier amplitude spectrum of ground motion acceleration, FS(f), may in fact be a preferred predictor of peak response, especially in a frequency range close to f. Other statistical methods (attenuation laws) use distance R and other parameters such as magnitude (M), Modified Mercalli epicentral Intensity (Io) and Modified Mercalli site Intensity (MMI or Is) to predict spectral velocity (Sv(f)), etc. In using such approaches, it is most desirable to know the total uncertainty in the predicted peak response of the system given the starting parameter values. An extensive strong motion data set is used to study these questions, The most direct prediction models are found to be preferable (have lower prediction dispersion) but data may not be available in all regions to permit their use.  相似文献   

4.
Arias Intensity (Arias, MIT Press, Cambridge MA, pp 438–483, 1970) is an important measure of the strength of a ground motion, as it is able to simultaneously reflect multiple characteristics of the motion in question. Recently, the effectiveness of Arias Intensity as a predictor of the likelihood of damage to short-period structures has been demonstrated, reinforcing the utility of Arias Intensity for use in both structural and geotechnical applications. In light of this utility, Arias Intensity has begun to be considered as a ground-motion measure suitable for use in probabilistic seismic hazard analysis (PSHA) and earthquake loss estimation. It is therefore timely to develop predictive equations for this ground-motion measure. In this study, a suite of four predictive equations, each using a different functional form, is derived for the prediction of Arias Intensity from crustal earthquakes in New Zealand. The provision of a suite of models is included to allow for epistemic uncertainty to be considered within a PSHA framework. Coefficients are presented for four different horizontal-component definitions for each of the four models. The ground-motion dataset for which the equations are derived include records from New Zealand crustal earthquakes as well as near-field records from worldwide crustal earthquakes. The predictive equations may be used to estimate Arias Intensity for moment magnitudes between 5.1 and 7.5 and for distances (both rjb and rrup) up to 300 km.  相似文献   

5.
以编制《中国地震动参数区划图》时所构建的地震潜在震源区模型和地震活动性模型为基本输入,在四川省丹棱县及其周缘地区开展基于阿里亚斯烈度的概率地震危险性分析,计算50年超越概率10%的阿里亚斯烈度(Arias Intensity,Ia)。结果表明:丹棱县及其周缘绝大部分地区的Ia值都在0.11m/s以上,部分地区在0.32m/s甚至0.54m/s以上,具有较高的地震诱发滑坡风险,应当加强人员密集区的地震诱发滑坡危险性评估。根据不同Ia预测方程计算得到的Ia分布有较大差异,因此在计算Ia时应考虑多个Ia预测方程,对最终结果进行加权平均,以减小Ia结果的不确定性。同时还发现Ia值与1.0s的谱加速度具有很好的相关性,这也印证了Ia和1.0s谱加速度与砂土液化的相关性。  相似文献   

6.
The parameters of S-wave attenuation (the total effect of absorption and scattering) near the Petropavlovsk (PET) station in Kamchatka were estimated by means of the spectral method through an original procedure. The spectral method typically analyzes the changes with distance of the shape of spectra of the acceleration records assuming that the acceleration spectrum at the earthquake source is flat. In reality, this assumption is violated: the source acceleration spectra often have a high-frequency cutoff (the source-controlled fmax) which limits the spectral working bandwidth. Ignoring this phenomenon not only leads to a broad scatter of the individual estimates but also causes systematic errors in the form of overestimation of losses. In the approach applied in the present study, we primarily estimated the frequency of the mentioned high-frequency cutoff and then constructed the loss estimates only within the frequency range where the source spectrum is approximately flat. The shape of the source spectrum was preliminarily assessed by the approximate loss compensation technique. For this purpose, we used the tentative attenuation estimates which are close to the final ones. The difference in the logarithms of the spectral amplitudes at the edges of the working bandwidth is the input for calculating the attenuation. We used the digital accelerograms from the PET station, with 80 samples per second digitization rate, and based on them, we calculated the averaged spectrum of the S-waves as the root mean square along two horizontal components. Our analysis incorporates 384 spectra from the local earthquakes with M = 4–6.5 at the hypocentral distances ranging from 80 to 220 km. By applying the nonlinear least-square method, we found the following parameters of the loss model: the Q-factor Q0 = 156 ± 33 at frequency f = 1 Hz for the distance interval r = 0–100 km; the exponent in the power-law relationship describing the growth of the Q-factor with frequency, γ = 0.56 ± 0.08; and the loss parameter beneath the station κ0 = 0.03 ± 0.005 s. The actual accuracy of the estimates can probably be somewhat lower than the cited formal accuracy. It is also established (with a confidence level of 10%) that the losses decrease with distance.  相似文献   

7.
A collection of ground‐motion recordings (1070 acceleration records) of moderate (5.1⩽ML⩽6.5) earthquakes obtained during the execution of the Taiwan Strong Motion Instrumentation Program (TSMIP) since 1991 was used to study source scaling model and attenuation relations for a wide range of earthquake magnitudes and distances and to verify the models developed recently for the Taiwan region. The results of the analysis reveal that the acceleration spectra of the most significant part of the records, starting from S‐wave arrival, can be modelled accurately using the Brune's ω‐squared source model with magnitude‐dependent stress parameter Δσ, that should be determined using the recently proposed regional relationships between magnitude (ML) and seismic moment (M0) and between M0 and Δσ. The anelastic attenuation Q of spectral amplitudes with distance may be described as Q=225 ƒ1.1 both for deep (depth more than 35 km) and shallow earthquakes. The source scaling and attenuation models allow a satisfactory prediction of the peak ground acceleration for magnitudes 5.1⩽M⩽6.5 and distances up to about 200 km in the Taiwan region, and may be useful for seismic hazard assessment. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

8.
Near-field horizontal and vertical earthquake ground motions   总被引：8，自引：0，他引：8  
Strong-motion attenuation relationships are presented for peak ground acceleration, spectral acceleration, energy density, maximum absolute input energy for horizontal and vertical directions and for the ratio of vertical to horizontal of these ground motion parameters. These equations were derived using a worldwide dataset of 186 strong-motion records recorded with 15 km of the surface projection of earthquakes between Ms=5.8 and 7.8. The effect of local site conditions and focal mechanism is included in some of these equations.  相似文献   

9.
ＧｅｎｅｒａｔｉｎｇｇｒｏｕｎｄｍｏｔｉｏｎｂｙｔｗｏｎｅｗｔｅｃｈｎｉｑｕｅｓｏｆａｄｄｉｎｇｈａｒｍｏｎｉｃｗａｖｅｉｎｔｈｅｔｉｍｅｄｏｍａｉｎａｎｄａｐｐｒｏｘｉｍａｔｉｎｇｔｏｒｅｓｐｏｎｓｅｓｐｅｃｔｒｕｍａｓａｗｈｏｌｅＣＨＡＮＧ...  相似文献   

10.
2020年1月19日和2020年2月21日在新疆喀什地区先后发生MS6.4和MS5.1地震,针对新疆强震动台网收集到的128条强震动记录进行统计分析,研究2次地震记录的幅值及反应谱特性,并与两个现行规范设计反应谱进行对比,结果表明：(1)震级相同时,震中距越小加速度反应谱越大,且加速度反应谱衰减速度越慢;震中距相同时,震级越大加速度反应谱越大,且加速度反应谱衰减速度越慢;(2)震级越大加速度谱值、速度谱值、位移谱值越大;(3)MS6.4、MS5.1地震波加速度反应谱及其平均值曲线相近,与我国现行规范加速度反应谱相比差别很大。建议在新疆喀什地区采用基于当地强震记录的加速度反应谱进行结构抗震设计。  相似文献   

11.
—To estimate for the first time the typical relation between peak acceleration A max?, moment magnitude M W and hypocentral distance R for Kamchatka, 101 analog strong motion records for 1969–1993 were employed as the initial data set. Records of acceleration and velocity meters were obtained at 15 rock to medium-ground Kamchatkan sites from 33 earthquakes with M W = 4.5–7.8, at R = 30–250?km. A max values were determined from "true" acceleration time histories calculated by spectral deconvolution of digitized records. The maximum value over the two horizontal components was used as the A max value in the further analysis. With the scarce data available, there were no chances to determine reliably the whole A max?(M W ?,?R) average surface; thus the shape of this trend surface was determined on a theoretical basis and only the level was fitted to the data. The theoretical model employed included: (1) source spectrum: according to the Brune's spectral model; (2) point-source attenuation: as 1/R plus loss specified by Q(f) = 250?f 0.8; (3) finite-source correction for a disc-shaped incoherent source, its size depending on M W ?; (4) accelerogram duration: including source-dependent and distance-dependent terms; (5) A max value: based on random process representation. Distance trends calculated with this model agree with the empirical ones of FUKUSHIMA and TANAKA (1990). To calculate the absolute level for these trends, observed A max?(M W ?,?R) values were reduced to M W = 8, R = 100?km using the theoretical trends as reference. The median of the reduced values, A max?(8,?100), equal to 188?gal. was taken as the absolute reference level for the relation we sought. Note that in the process of data analysis we were forced to entirely reject relatively abundant data of two particular stations because of their prominent local amplification (×5.5) or deamplification (×0.45).  相似文献   

12.
对2013年7月22日甘肃岷县—漳县地震获取的273条主余震加速度记录进行格式转换、基线校正和滤波等常规处理,分析该地震主震(M_S6.6)和余震(M_S5.6)两次地震记录的幅值、持时以及反应谱特征,发现M_S6.6主震记录的PGA范围在0.728～177.5 gal间,M_S5.6余震记录的PGA范围在0.732～69.3 gal间;将观测数据与霍俊荣和第五代《中国地震动参数区划图》地震动衰减关系进行对比,发现霍俊荣衰减关系更吻合于此次地震的主余震加速度衰减;绘制主余震5%～95%重要持时分布图,并针对主震62MXT反应谱和本地设计谱以及近些年国内主要强震震中反应谱开展比较分析;最后研究土层台、基岩台、相同台站各个震级反应谱的特征。  相似文献   

13.
For short-period near-earthquake records in eastern China, from the empirical attenuation formula of coda ground motion amplitudeA with timeτ: lgA=G−2. 235 lgτ, using the single scattering theory modified with epicentral distance, we obtain the curve family of corrected coda amplitudeA c(r,t), andω/2Q c values for each time interval of coda. From this,Q c(f,h) values, which correspond to each observational average frequency and sampling depth, are calculated. The results substantially agree with those observationalQ c values in Yunnan, Beijing and central Asia.  相似文献   

14.
This paper presents the results of an investigation of the magnitude–intensity and intensity–attenuation relationships for earthquakes in the Atlas block and Algeria using macroseismic data. This work is based on a selected sample of isoseismal maps from 32 events which were recently revised. Surface-wave magnitudes, Ms, are recalculated using the Prague formula and range from 4·2 to 7·45. Because the Atlas mountains block is in a collision zone, earthquakes occur in general within a layer 15 km deep. Expressions of general form for the magnitude–intensity and intensity–attenuation correlations are adopted and are, respectively, and where R2 = d2 + h2, d the source distance in km, h the focal depth in km, Ms the revised surface-wave magnitude, Msc the predicted surface-wave magnitude, Ii the intensity at isoseismal i, I the predicted intensity, σ the standard deviation and P is zero for 50-percentile values and one for 84-percentile, and the coefficients A's and B's are determined by regression analysis. The results of this study show that the intensity–attenuation models are adequate to predict quite well the die-out of intensity with distance in the Atlas zone and coastal Algeria; it is also found that magnitude can be predicted accurately by calibrating isoseismal radii against revised instrumental surface-wave magnitude. Such magnitude–intensity relationships may be used to evaluate the magnitude of historical earthquakes in the region under survey, with no instrumental data, for which isoseismal radii and intensities are available.  相似文献   

15.
Predictive relations are developed for peak ground acceleration (PGA) from the engineering seismoscope (SRR) records of the 2001 Mw 7.7 Bhuj earthquake and 239 strong-motion records of 32 significant aftershocks of 3.1 ≤ Mw ≤ 5.6 at epicentral distances of 1 ≤ R ≤ 288 km. We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relation for peak horizontal acceleration in the Kachchh seismic zone, Gujarat. This new analysis uses the Joyner-Boore’s method for a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. The resulting attenuation equation is,
where, Y is peak horizontal acceleration in g, Mw is moment magnitude, rjb is the closest distance to the surface projection of the fault rupture in kilometers, and S is a variable taking the values of 0 and 1 according to the local site geology. S is 0 for a rock site, and, S is 1 for a soil site. The relation differs from previous work in the improved reliability of input parameters and large numbers of strong-motion PGA data recorded at short distances (0–50 km) from the source. The relation is in demonstrable agreement with the recorded strong-ground motion data from earthquakes of Mw 3.5, 4.1, 4.5, 5.6, and 7.7. There are insufficient data from the Kachchh region to adequately judge the relation for the magnitude range 5.7 ≤ Mw ≤ 7.7. But, our ground-motion prediction model shows a reasonable correlation with the PGA data of the 29 March, 1999 Chamoli main shock (Mw 6.5), validating our ground-motion attenuation model for an Mw6.5 event. However, our ground-motion prediction shows no correlation with the PGA data of the 10 December, 1967 Koyna main shock (Mw 6.3). Our ground-motion predictions show more scatter in estimated residual for the distance range (0–30 km), which could be due to the amplification/noise at near stations situated in the Kachchh sedimentary basin. We also noticed smaller residuals for the distance range (30–300 km), which could be due to less amplification/noise at sites distant from the Kachchh basin. However, the observed less residuals for the longer distance range (100–300 km) are less reliable due to the lack of available PGA values in the same distance range.  相似文献   

16.
Summary The darkening (S) of Illford Q2 photographic plates as ion detectors in mass spectrometer has been investigated. The dependence of the darkening (S) on the ion density (n=ions/mm2) i.e.S=S(n)E for constant energy (E)=z U ranging from 4U20 Kv of the impinging40A+1-,40A+2- and40A+3-ions whenS does not exceed the value 0.15 and the second relationn=n(z U) S for darkening 0.05S0.15 constructed from the above relationS=S(n) E has been determined. The darkening was found to increase with increasing ion-density which inturn decreases with the ionenergy. For40A+1-,40A+2-, and40A+3-ion of equal energy and ion-density the darkening effect was independent of the number of the charges carried by the argon ion.  相似文献   

17.
利用《中国地震动参数区划图》采用的地震动参数衰减关系,以及《中国地震动参数区划图》中地震动峰值加速度和地震动加速度反应谱特征周期反推不同设防烈度和设计地震分组对应的震级和震中距,再根据《建筑抗震设计规范》中各设防水准的峰值加速度确定对应的震级和震中距,进而根据地震动强度包线参数与震级和震中距关系计算地震动强度包线参数的取值,为基于强度包线函数生成人工地震动提供参考,并讨论强度包线参数的取值规律：(1)随着设防烈度的提高,加速度时程曲线上升段持续时间t1和平稳段持续时间ts减小,下降段衰减指数c增大;(2)随着地震水准和设计地震分组的提高,加速度时程曲线上升段持续时间t1和平稳段持续时间ts增加,下降段衰减指数c减小;(3)在生成人工地震动时,除考虑峰值加速度和设计地震分组影响外,还需要考虑设防烈度影响。  相似文献   

18.
There are recent observational indications (lack of convergent electric field signatures above the auroral oval at 4 RE altitude) that the U-shaped potential drop model for auroral acceleration is not applicable in all cases. There is nevertheless much observational evidence favouring the U-shaped model at low altitudes, i.e., in the acceleration region and below. To resolve the puzzle we propose that there is a negative O-shaped potential well which is maintained by plasma waves pushing the electrons into the loss cone and up an electron potential energy hill at 3/4RE altitude range. We present a test particle simulation which shows that when the wave energization is modelled by random parallel boosts, introducing an O-shaped potential increases the precipitating energy flux because the electrons can stay in the resonant velocity range for a longer time if a downward electric field decelerates the electrons at the same time when waves accelerate them in the parallel direction. The lower part of the O-shaped potential well is essentially the same as in the U-shaped model. The electron energization comes from plasma waves in this model, but the final low-altitude fluxes are produced by electrostatic acceleration. Thus, the transfer of energy from waves to particles takes places in an energization region, which is above the acceleration region. In the energization region the static electric field points downward while in the acceleration region it points upward. The model is compatible with the large body of low-altitude observations supporting the U-shaped model while explaining the new observations of the lack of electric field at high altitude.  相似文献   

19.
By the use of the model of approaching drops (Arbel and Levin, 1977) the coalescence efficiencies of drops are computed. It is found that for interactions of drops at their terminal velocities the coalescence depends both on the size of the large drop and on the size ratio of the interacting drops in agreement with the experimental results of Whelpdale and List (1971) and Levin and Machnes (1977).The results were found to be sensitive to the assumption of the drops deformation and to the critical separation distance. This distance is defined as the distance at which the drops begin to merge. The variations of the coalescence efficiency with these parameters is discussed.Appendix: List of symbols D distance between the deformed surfaces of the drops - D o initial value ofD - D s stop distance, the distance at which the impact velocity vanishes - D c critical coalescence distance - E collection efficiency - E 1 collision efficiency - E 2 coalescence efficiency - E 2R coalescence efficiency for collisions with stationary targets - F c centrifugal force - p ratio of the radii of the interacting drops - r o initial distance between drops' centers - R L radius of larger drop - R s radius of smaller drop - R D radius of deformation - v approach velocity of two deformed surfaces - v o initial value ofv - V i impact velocity (given negative sign when drops approach each other) - V c critical impact velocity - W i velocity of the smaller drop at infinity for it to reachD o with velocityv o - x i impact distance, the distance between the trajectories of the two drops - x c critical impact distance for coalescence -  average critical impact distance for coalescence - X c critical impact distance for collisions - coefficient of deformation given in equation 1 - i impact angle defined byWhelpdale andList (1971) given also inArbel andLevin (1977) - coefficient of deformation given in equation 2 - viscosity of air - i impact angle used inArbel andLevin (1977) and here - c critical angle for coalescence - average critical angle for coalescence On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

20.
Scaling properties of Canadian low flows, namely annual minimum mean 1-, 5- and 7-day flows, are evaluated across Canada and in its sub-climatic regions. Across the entire country, the log relationship between the kth product moments (PMs, E[Qik]) of low flows and drainage area (Ai) can be represented by: ln(E[Qik])=ak+bkln(Ai)and bk=k, with = 0.86, 0.94 and 0.93 for annual minimum mean 1-, 5- and 7-day flows, respectively. The log linear relationships between the kth probability weighted moments (PWMs, ) and Ai are ln()=ck+Hln(Ai), in which H is constant and is independent of k. The values of H are 0.87, 0.97, and 0.96 for annual minimum mean 1-, 5- and 7-day flows, respectively, which are almost the same as the values. The coefficients of variation (Cv) are almost independent of drainage area. These results demonstrate that Canadian low flows generally exhibit simple scaling and drainage area alone describes most of the variability in the moments of the low flows. Low flows in each of the sub-climatic regions also obey a simple scaling law. The values of , H and Cv are different in each region, which may stem from physiographical and climatological differences among these regions. The finding lays a basis for applying the index flood method to conduct regional low flow frequency analysis as simple scaling is equivalent to the index flood method.Acknowledgements The authors thank Prof. Thian Yew Gan of University of Alberta, Canada for providing additional pristine data sites for regions 4 and 10. A constructive comments provided by an anonymous reviewer improved the quality of the paper.  相似文献   

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