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1.
Dependence of the energy released during earthquake on ambient shear stress   总被引：1，自引：0，他引：1  
Starting with dislocation model, using the result of the fracture mechanics: the slip displacement at the crack tip is proportional to the length of the crack and the applied ambient shear stressτ 0 2 , we consider the dislocation in the earthquake to be the slip displacement at the crack tip and have obtained the analysis expresses of displacement and velocity pulse for the circular crack and have calculated the seismic wave energy radiated by earthquake. The seismic wave energyE ∞M 0 τ 0 2 f(v) r , i. e.E is proportional to the seismic momentM 0 and the square of the ambient shear stressτ 0 2 and increases with the rupture velocityv r . In frequency domain, integrating the square of source velocity spectrum derived from our the scaling law model, we have also obtained the seismic wave energyE released by earthquake and earthquake radiated effficiencyη.E ∞M 0 τ 0 2 also. If takingτ 0 = 10.0 MPa, E=4.79M 0. This result is consistent with the estimate by Vassiliou and Kanamori (1982). Theη=5.26%. The distribution of the seismic wave energy is that most of the energy contains in the frequency range between the first corner frequencyf c1 and thirdf c3, amount to 92.3% the energy in the rangef<f c1 is about 3.85% and 3.85% whenf>f c3. Thef c3 is about 8Hz forM ⩾ 6, thus most of radiated energy is below 2Hz. This phenomenon had been verified by Vassiliou Kanamori. Previous results show the energy radiated by earthquake to be strongly dependent on ambient shear stress. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 146–152, 1993. This work was supported by the Deutsche Forschungsgemeinschaft, Bonn, F. R. Germany. The support is grateful acknowledged. The authors are also grateful to Professor Klussmann and Mr. Hasthoff for their lots of help.  相似文献   

2.
When formulated properly, most geophysical transport-type process involving passive scalars or motile particles may be described by the same space–time nonlocal field equation which consists of a classical mass balance coupled with a space–time nonlocal convective/dispersive flux. Specific examples employed here include stretched and compressed Brownian motion, diffusion in slit-nanopores, subdiffusive continuous-time random walks (CTRW), super diffusion in the turbulent atmosphere and dispersion of motile and passive particles in fractal porous media. Stretched and compressed Brownian motion, which may be thought of as Brownian motions run with nonlinear clocks, are defined as the limit processes of a special class of random walks possessing nonstationary increments. The limit process has a mean square displacement that increases as tα+1 where α > −1 is a constant. If α = 0 the process is classical Brownian, if α < 0 we say the process is compressed Brownian while if α > 0 it is stretched. The Fokker–Planck equations for these processes are classical ade’s with dispersion coefficient proportional to tα. The Brownian-type walks have fixed time step, but nonstationary spatial increments that are Gaussian with power law variance. With the CTRW, both the time increment and the spatial increment are random. The subdiffusive Fokker–Planck equation is fractional in time for the CTRW’s considered in this article. The second moments for a Levy spatial trajectory are infinite while the Fokker–Planck equation is an advective–dispersive equation, ade, with constant diffusion coefficient and fractional spatial derivatives. If the Lagrangian velocity is assumed Levy rather than the position, then a similar Fokker–Planck equation is obtained, but the diffusion coefficient is a power law in time. All these Fokker–Planck equations are special cases of the general non-local balance law.  相似文献   

3.
Ｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆａｍｂｉｅｎｔｓｔｒｅｓｓｖａｌｕｅｓｆｏｒｍｉｃｒｏ－ｅａｒｔｈｑｕａｋｅｓｅｑｕｅｎｃｅｓｉｎＷｅｓｔｅｒｎＹｕｎｎａｎ　Ｅａｒｔｈｑｕａｋｅ　Ｐｒｅｄｉｃｔｉｏｎ　Ｅｘｐｅｒｉｍｅｎｔａｌ　ＦｉｅｌｄＪｉａ－Ｚ...  相似文献   

4.
Microseismic noise was studied in the frequency range 0.5–30 Hz in the conditions prevailing in the town of Vorkuta. A seismic noise model was developed consisting of power spectral densities of ground motion velocity separately for daytime and nighttime in different frequency ranges. The absolute noise level for frequencies of 1–5 Hz in Vorkuta varies between −140 and −150 dB in daytime and from −152 to −158 dB in nighttime, with the ranges for the 8-15 Hz noise being −140 to −155 dB in daytime and −155 to −165 dB in nighttime. Well-pronounced daily variations in noise amplitude were observed in the frequency ranges 1.5–3 Hz and 14–17 Hz. The noise amplitude varies by 7 dB over 24 hours, with the amplitude of horizontal component variation being 5 dB above that of the vertical component. The power spectral densities of ground motion velocity in the microseismic noise involve several spectral peaks, whose central frequencies did not vary by more than 0.15 Hz during the entire period of instrumental observation. The seismic background in the town of Vorkuta contains seismic events due to distant earthquakes and local industrial explosions.  相似文献   

5.
Ａｌｉｇｎｍｅｎｔｓｉｌｋｗｏｒｍｓａｓｓｅｉｓｍｉｃａｎｉｍａｌａｎｏｍａｌｏｕｓｂｅｈａｖｉｏｒ（ＳＡＡＢ）ａｎｄｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｍｏｄｅｌｏｆａｆａｕｌｔ：ａｔｈｅｏｒｙａｎｄｌａｂｏｒａｔｏｒｙｅｘｐｅｒｉｍｅｎｔＭＯＴＯ...  相似文献   

6.
A detailed representation of variations of the total solar flux I has been obtained by analyzing the regular measurements of this flux by the Nimbus-7 and other spacecrafts. In particular, quasi-biennial variations (QBVs) of the monthly average value 〈I〉 and standard deviation sI within a month interval have been revealed. It is remarkable that the QBVs of sI almost coincide in shape with the QBVs of many solar activity and ionospheric indices, and the QBVs of 〈I〉 are almost in antiphase with the variations of sI. The manifestation of the QBVs of 〈I〉 in some processes on the Earth has been already revealed. A relation between the QBVs of 〈I〉 for solar radiation (according to the Nimbus-7 and ACRIM-2 data) and the QBVs of the zonal stratospheric wind near the equator, as well as the QBVs of the Earth’s rotation velocity, has been found. Many of the considered QBV-processes on the Earth are seemingly attributed to the variations of the total solar flux.  相似文献   

7.
This paper presents an analysis of the distribution of the time τ between two consecutive events in a stationary point process. The study is motivated by the discovery of unified scaling laws for τ for the case of seismic events. We demonstrate that these laws cannot exist simultaneously in a seismogenic area. Under very natural assumptions we show that if, after rescaling to ensure Eτ =1, the interevent time has a universal distribution F, then F must be exponential. In other words, Corral’s unified scaling law cannot exist in the whole range of time. In the framework of a general cluster model we discuss the parameterization of an empirical unified law and the physical meaning of the parameters involved. An erratum to this article is available at .  相似文献   

8.
For any earthquake, the slipping fault and the source of high-frequency seismic waves, by and large, coincide. On a more local scale, however, the areas of high seismic slip rate and of increased high-frequency radiation output (seismic luminosity) need not match. To study in some detail how slip rate and seismic luminosity are interrelated, a systematic study is performed that uses 251 records of teleseismic P waves from 23 intermediate-depth earthquakes of magnitude 6.8 and above. From a broadband trace we extract two time histories: (1) displacement and (2) 0.5–2.5 Hz band-passed and squared velocity, or ``HF power', and calculate correlation coefficient, ρ between the two. To reduce the bias related to formation of P coda, a special procedure is applied to data. We estimated the average value ρ = 0.52 (range of event averages 0.35 to 0.65) for the correlation coefficient between the radiated time histories for displacement and ``HF power', which is considerably below the ``ideal' value of unity. We argue that the same or even lower value characterizes the degree of slip rate - seismic luminosity correlation at the fault. Two factors may contribute to the revealed decorrelation: (1) random fluctuations of observed HF power (inevitable for a signal with a limited bandwidth), and (2) the genuine mismatch of slip rate and mean luminosity. We show that these factors, acting separately, would result in the ρ values equal to, correspondingly, 0.72 and 0.80. We also show that genuine decorrelation is statistically significant. We conclude that the observed values of ρ indicate genuine differences between the distributions of the slip rate and the seismic luminosity over the fault area. These results provide important constraints both for the accurate wide-band simulation of strong ground motion and for theoretical dynamic source models.  相似文献   

9.
The understanding of geotechnical characteristics of near-surface material is of fundamental interest in seismic microzonation. Shear wave velocity (Vs), one of the most important soil properties for soil response modeling, has been evaluated through seismic profiling using the multichannel analysis of surface waves in the city of Dehradun situated along the foothills of northwest Himalaya. Fifty sites in the city have been investigated with survey lines between 72 and 96 m in length. Multiple 1-D and interpolated 2-D profiles have been generated up to a depth of 30–40 m. The Vs were used in the SHAKE2000 software in combination with seismic input motion of the recent Chamoli earthquake to obtain site response and amplification spectra. The estimated Vs are higher in the northern part of the study area (i.e., 200–700 m/s from the surface to a depth of about 30 m) as compared to the south and southwestern parts of the city (i.e., 180–400 m/s for the same depth range). The response spectra suggest that spectral acceleration values for two-story structures are three to eight times higher than peak ground acceleration at bedrock. The analysis also suggests peak amplification at 3–4, 2–2.5, and 1–1.5 Hz in the northern, central, and south-southwestern parts of the city, respectively. The spatial distributions of Vs and spectral accelerations provide valuable information for the seismic microzonation in different parts of the urban area of Dehradun.  相似文献   

10.
Follow Chen and Duda's model of spectral fall-off of (3, the dependence of peak parameters of ground motion, peak displacement dm, peak velocity vm and peak acceleration am, upon the environment stress (0-values are studied using near source seismic digital recordings for the sequence of the Wuding, Yunnan, M = 6.5 earthquake, in which, as a new thought, the peak parameters are assumed to be related to the medium Q-value. Three formulae for estimating the environment stress (0-values by the peak parameters of three types of ground motions are derived. Using these formulae, the environment stress (0-values are calculated for the sequence of the Wuding earthquake. The result show that (0-values calculated by the three formulae are constant largely, the averages of (0 are in the range of 5.0～35 MPa for most earthquakes. It belongs to the high-stress earthquakes sequence: the high-stress values are restricted to the relatively small area closely near to the epicenter of the main shock. The fine distribution structure for the contours of the environment stress (0-values is related closely to the strong aftershocks. The analysis of spatial and temporal feature of (0-values suggests that the earthquakes sequence in a rupture process generated at the specific intersection zone of seismo-tectonics under high-stress background.  相似文献   

11.
Two approaches for the modelling of turbulence in vegetated flows have been developed in the past. The “microscopic” approach which is straightforward but limited to simple cases and the “macroscopic” approach which is based on Volume Average Theory (VAT). In this study, aspects of Volume-Average (VA) analysis and modelling are investigated for turbulent vegetated flow using computed three-dimensional results from the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations around a representative vegetal element. In particular (a) the VA transport equations for k and ε, based on VAT, are properly derived, (b) the Boussinesq hypothesis for the VA quantities, employed in 〈k〉-〈ε〉 turbulence models is tested, and (c) the values of the coefficients used in such turbulence models are assessed in comparison with those used in the classical turbulence models.  相似文献   

12.
Non‐linear dynamic time‐history analyses conducted as part of a performance‐based seismic design approach often require that the ground motion records are scaled to a specified level of seismic intensity. Recent research has demonstrated that certain ground motion scaling methods can introduce a large scatter in the estimated seismic demands. The resulting demand estimates may be biased, leading to designs with significant uncertainty and unknown margins of safety, unless a relatively large ensemble of ground motion records is used. This paper investigates the effectiveness of seven ground motion scaling methods in reducing the scatter in estimated peak lateral displacement demands. Non‐linear single‐degree‐of‐freedom systems and non‐linear multi‐degree‐of‐freedom systems are considered with different site conditions (site soil profile and epicentral distance) and structural characteristics (yield strength, period, and hysteretic behavior). It is shown that scaling methods that work well for ground motions representative of stiff soil and far‐field conditions lose their effectiveness for soft soil and near‐field conditions for a wide range of structural characteristics. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

13.
The 2009 Mw 6.3 L’Aquila event caused extensive damage in the city of L’Aquila and in some small towns in its vicinity. The most severe damage was recognized SE of L’Aquila town along the Aterno river valley. Although building vulnerability and near-source effects are strongly responsible for the high level of destruction, site effects have been invoked to explain the damage heterogeneities and the similarities between the 2009 macroseismic field with the intensities of historical earthquakes. The small village of Onna is settled on quaternary alluvium and suffered during the L’Aquila event an extremely heavy damage in the masonry structures with intensity IX–X on the Mercalli-Cancani-Sieberg (MCS) scale. The village of Monticchio, far less than 1.3 km from Onna, is mostly situated on Mesozoic limestone and suffered a smaller level of damaging (VI MCS). In the present paper, we analyze the aftershock recordings at seismic stations deployed in a small area of the middle-Aterno valley including Onna and Monticchio. The aim is to investigate local amplification effects caused by the near-surface geology. Because the seismological stations are close together, vulnerability and near-source effects are assumed to be constant. The waveform analysis shows that the ground motion at Onna is systematically characterized by large high-frequency content. The frequency resonance is varying from 2 to 3 Hz and it is related to alluvial sediments with a thickness of about 40 m that overlay a stiffer Pleistocene substrate. The ground motion recordings of Onna are well reproduced by the predictive equation for the Italian territory.  相似文献   

14.
The empirical equations for scaling Fourier amplitude spectra in the frequency band from ~0·1 to 25 Hz can be extrapolated to describe the long period strong motion amplitudes. The results of this extrapolation can agree with (1) the seismological and field estimates of permanent ground displacement (near field), and with (2) the independent estimates of seismic moment and the observed frequencies of far field Fourier spectrum amplitudes.  相似文献   

15.
The theoretical acceleration spectrum of observation site has been obtained from source acceleration spectrum derived from scaling law, using attenuation modelQ=Q ν f η . A comparison of a set of theoretical acceleration spectra with observation spectra has been made, and we have obtained the attenuation model for observation site and seismic moment magnitude. We obtain thatQ o=300,η=0.25 for Wuqia area, Xinjing Zizhizhou, and seismic moment magnitudes of 18 greater aftershocks of Wuqia earthquake occurred in 1985. In order to obtain seismic moment magnitued conveniently, three functional tables of acceleration spectra at 1Hz as the distances for variousQ value have been made. The seismic moment magnitude can be quickly measured from acceleration spectrum at 1Hz according to these tables (epicenter has to be known). The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 435–445, 1992.  相似文献   

16.
ＥｓｔｉｍａｔｉｏｎｏｆｓｅｉｓｍｉｃｓｔｒｅｓｄｒｏｐｆｒｏｍｔｈｅｐｅａｋｖｅｌｏｃｉｔｙｏｆｇｒｏｕｎｄｍｏｔｉｏｎＪＩＡＺＨＥＮＧＱＩＮ（秦嘉政）ＺＵＹＩＮＬＩＵ（刘祖荫）ＸＩＡＯＤＯＮＧＱＩＡＮ（钱晓东）ＱＩＮＧＹＩＮＸＩＥ（谢庆...  相似文献   

17.
It is shown how the empirical equations for scaling the Fourier amplitude spectra in the frequency band from ～0.1 to 25 Hz can be extended to describe the strong motion amplitudes in a much broader frequency range. At long periods, the proposed equations are in excellent agreement with (1) the seismological and field estimates of permanent ground displacement (near field) and (2) the independent estimates of seismic moment (far field). At high frequencies, f ≥ 25 Hz, the spectral amplitudes can be described by exp (? πkf), where k ranges from 0·02 (near source) to about 0·06 at an epicentral distance of about 200 km. It is also shown how amplification by local soil and geological site conditions can be defined to apply in the same broad frequency range.  相似文献   

18.
Detrended fluctuation analysis (DFA) and power spectrum density are applied to verify the presence of temporal scaling behavior and long-range persistence (LRP) of weekly hydrogen ion deposition (WHD), NO3- and SO42- deposition series in National Atmospheric Deposition Program, USA, for the period 1978–2001. The results show a common scaling behavior for all sites analyzed. Two distinct scaling regions are identified by DFA1, one corresponding to 1 month to 1 year and the other to 1 year to 5 years. The WHD series obey power-law in two temporal regimes respectively with mean DFA1 scaling exponents α 1≈0.68 and α 2≈0.45, implying the presence of LRP in the acid deposition series and there is a tendency for a large deposition event to be followed by another large event, and vice versa. For DFA2–DFA4, however, the annual crossover, which divides the temporal scale into two regimes, disappears gradually with the order q of DFAq increasing, and the two scaling regimes turn to share the same scaling exponent close to α 1. The result indicates that the scaling behavior exits in the two regimes with the same scaling exponent α 1, and LRP prevails during the examined 1-month to 5-years scale. NO3- and SO42- deposition evolve the same way as WHD does, implying the pollutants involving in acid deposition may share some prominent mechanism controlling their evolutions. We ascribe the long-range power-law scaling of acid deposition evolutions to the self-organized critical behavior of atmosphere under pollution stress and it should be considered in the trend prediction of acid deposition as an important factor.  相似文献   

19.
Local Site Effects in the Town of Benevento (Italy) from Noise Measurements   总被引：2，自引：0，他引：2  
— The study of ground motion amplification produced by surface geology is extremely interesting in the Benevento area, Southern Italy, as it is characterized by high seismic hazard. The present moderate-to-low seismicity makes the noise method appropriate to estimate the seismic site response in the area. The three components of seismic noise have been recorded in five sites in the Benevento metropolitan area characterized by different surface geology, in order to estimate the seismic site response. In evaluating site amplification effects we used the direct interpretation of amplitude spectra and standard spectral ratio techniques, evaluating sediment-to-bedrock, sediment-to-average and H/V spectral ratios. The temporal evolution of the noise spectra is analysed within one day, in order to assess the stationarity of the noise signal. The noise wavefield properties have been studied through polarization analyses in selected bands of frequency, where spectral peaks are observed to dominate, to better understand the real nature of those peaks. Results give evidence of low amplification levels, missing any correlation between spectral amplitudes and sediment thickness over the basement. We interpret this result as due to the poor impedance contrast between sediments and basement, which is characterized by low values of shear waves velocity. Moreover, sharp amplitude peaks are observed in the raw spectra of the sediment-sites, in the 2–4 Hz frequency band; a numerical simulation interprets this effect as possibly associated with a wide-scale structure, invoking the presence of a sharper impedance contrast at greater depth. At high frequencies the action of ambient noise sources, mainly active on horizontal components of motion, is retained dominant to generate the prominent peaks observed in the H/V spectral ratios; in some cases the presence of a near-surface low-velocity layer can contribute to amplify the seismic motion generated at these frequencies.  相似文献   

20.
In this study near field strong ground motion generation of Mw 6.9 scenario events on Gemlik Bay was presented at broadband frequency (0.5–10 Hz) ground motion at 9 stations. In the first stage of the study, focal mechanism of a small earthquake, which was used as the Empirical Green’s Function (EGF) throughout the scenario simulation, was decided by simulating it with a smaller magnitude event. The best waveform fitting was judged with the smallest misfit value. In the second stage, near field ground motion simulation of scenario events was performed. Calculations were achieved by considering three different rupture processes which have the same magnitude but different asperity locations. Fault and asperity parameters for each scenario were determined from empirical scaling laws. It has been found that the peak ground acceleration and peak ground velocities reach maximum values of 1,440 cm/s2 and 125 cm/s, respectively for the worst case scenario. Rupture directivity effect is observed with clear peaks at a forward station. The design spectra for Turkish seismic design code (TSDC 2007) were either nearly or actually exceeded by the scenario earthquakes at periods lower than 0.6  s at all near field stations. Majority of structures in the area were built to lower design spectra before the 1998 code was implemented. The strength of many structures would have been insufficient to resist the forces that may be generated by an earthquake that is similar to Scenario I and Scenario II in this study.  相似文献   

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