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1.
The regularities in the radiation and propagation of seismic waves within the Baikal Rift Zone in Buryatia are studied to estimate the ground motion parameters from the probable future strong earthquakes. The regional parameters of seismic radiation and propagation are estimated by the stochastic simulation (which provides the closest agreement between the calculations and observations) of the acceleration time histories of the earthquakes recorded by the Ulan-Ude seismic station. The acceleration time histories of the strongest earthquakes (M W ~ 3.4–4.8) that occurred in 2006–2011 at the epicentral distances of ~96–125 km and had source depths of ~8–12 km have been modeled. The calculations are conducted with estimates of the Q-factor which were previously obtained for the region. The frequency-dependent attenuation and geometrical spreading are estimated from the data on the deep structure of the crust and upper mantle (velocity sections) in the Ulan-Ude region, and the parameters determining the wave forms and duration of acceleration time histories are found by fitting. These parameters fairly well describe all the considered earthquakes. The Ulan-Ude station can be considered as the reference bedrock station with minimum local effects. The obtained estimates for the parameters of seismic radiation and propagation can be used for forecasting the ground motion from the future strong earthquakes and for constructing the seismic zoning maps for Buryatia. 相似文献
2.
High-damping response spectra are essential tools for the assessment and design methods based on the equivalent elastic structure
concept. They are also often used for the analysis and design of structures with seismic isolation or energy dissipation systems.
Many formulations of the reduction factors have been proposed and included in seismic codes to estimate high-damping response
spectra from their 5% damping representation. They are reviewed in the present paper. The accuracy of each of them in estimating
the maximum elastic response of structures with viscous damping ratios greater than 5% is assessed by comparing exact and
approximate displacement response spectra for three different damping levels, namely 10, 20 and 30%, respectively. The comparison
is referred to more than 120 ground motion records, relevant to earthquakes with magnitude between 6 and 8, epicentral distance
ranging from 1 to 100 km and Peak Ground Accelerations (PGA’s) greater than 0.1 g. The comparison between exact and approximate
response spectra is carried out for both single earthquakes and groups of earthquakes with similar magnitude and epicentral
distance. The drawbacks of using the same damping reduction factor to estimate both maximum displacement response and design
seismic forces are also addressed. 相似文献
3.
Ground-motion prediction equations for the intermediate depth Vrancea (Romania) earthquakes 总被引：2，自引：1，他引：1
Vladimir Sokolov Klaus-Peter Bonjer Friedemann Wenzel Bogdan Grecu Mircea Radulian 《Bulletin of Earthquake Engineering》2008,6(3):367-388
We present the regional ground-motion prediction equations for peak ground acceleration (PGA), peak ground velocity (PGV),
pseudo-spectral acceleration (PSA), and seismic intensity (MSK scale) for the Vrancea intermediate depth earthquakes (SE-Carpathians)
and territory of Romania. The prediction equations were constructed using the stochastic technique on the basis of the regional
Fourier amplitude spectrum (FAS) source scaling and attenuation models and the generalised site amplification functions. Values
of considered ground motion parameters are given as the functions of earthquake magnitude, depth and epicentral distance.
The developed ground-motion models were tested and calibrated using the available data from the large Vrancea earthquakes.
We suggest to use the presented equations for the rapid estimation of seismic effect after strong earthquakes (Shakemap generation)
and seismic hazard assessment, both deterministic and probabilistic approaches. 相似文献
4.
We present the frequency-dependent attenuation model for Fourier amplitude spectra of strong earthquake ground motion in Serbia from intermediate depth earthquakes in the Vrancea source zone in Romania. The development of this type of scaling is the essential first step toward developing the corresponding attenuation and scaling equations for pseudo relative velocity spectra (PSV), which are necessary for seismic macro- and microzoning in the territory of Serbia. Such scaling is necessary because the Vrancea source zone produces large earthquakes with shaking that attenuates differently from the local earthquakes in Serbia. Development of such a scaling model is associated with several difficulties, the principal one being the lack of recorded strong motion accelerograms at epicentral distances exceeding 300 km. To reduce uncertainties with such scaling, we require our preliminary scaling equations to be consistent with independent estimates of seismic moment, stress drop, and radiated wave energy. In the future, when the recorded strong motion data from Vrancea earthquakes increases several-fold of what it is today, it will become possible to perform this analysis again, thus leading to more reliable and permanent scaling estimates. 相似文献
5.
6.
Our previous studies show that site effects (amplification of rock motions), source and path effects are coupled when response spectra are used to characterize the amplification ratios for a soil site modelled as nonlinear or elastic. The coupling is referred to as a “side effect” of using response spectral amplification ratios. In the present study we use a suite of rock site records, well distributed with respect to magnitude and source distance, from crustal, subduction interface and slab earthquakes to evaluate the response spectral amplification ratio for soft soil sites. We compare these side-effects for ground motions generated by three types of earthquakes, and we find that, at periods much shorter or much longer than the natural period of a soil site modelled as elastic, the average amplification ratios with respect to rock site ground motions from three types of earthquakes are moderately different and are very similar for other spectral periods. These differences are not statistically significant because of the moderately large scatter of the amplification ratios. However, the extent of magnitude- and source-distance-dependence of amplification ratios differs significantly. After the effects of magnitude and source distance on the amplification ratios are accounted for, the differences in amplification ratios between crustal and subduction earthquake records are very large in some particular combinations of source distance and magnitude range. These findings may have potential impact in establishing design spectra for soft soil sites using strong motion attenuation models or numerical modelling. 相似文献
7.
Cvetan Sinadinovski Lazo Pekevski Dragi Dojcinovski Dragana Cernih 《Journal of Seismology》2018,22(6):1451-1467
During the months of June–July 2017, the Lake Ohrid area in the southwestern Macedonia experienced a series of small to intermediate earthquakes. More than a thousand earthquakes occurred in that period, all in the epicentral area about 10 km east-northeast from Ohrid city center. The earthquakes showed characteristics of a swarm with 50 of them having magnitudes of 3 or greater and the strongest reaching magnitude M5.0. The earthquakes caused concern among the people in Ohrid and neighboring cities and villages and prompted the installation of two networks of temporary stations. One network was deployed in the epicentral area to determine in more detail the earthquakes’ depth and source parameters. The other urban network of instruments was installed to monitor the influence of the ground on the amplification of shaking and the dynamics of structures in the city of Ohrid. In this study, a selection of the urban network strong motion (SM) records was analyzed for the first time. Accelerograph records from a magnitude M3.1 earthquake recorded at eight places in the city and from the two earthquakes with magnitudes M4.2 and M5.0 recorded at the permanent seismological station Ohrid (code OHR) were used. The results of the behavior of the instrumented building were also compared with the findings of previous experiments. The differences in the spectral values on the SM records from the stations were investigated in respect to the ground conditions and location where the instruments were installed, i.e., bedrock and sediments at the sites. The power spectra and the H/V ratio of the earthquake records from the 2017 seismic sequence in the Ohrid area were also viewed in respect to the Eurocode-8. In addition to being used as part of standard engineering practice, this information about the local soil conditions can be of interest to geophysicists in seismic and geotechnical investigations, as well as in seismic risk-assessment applications. 相似文献
8.
O. V. Pavlenko 《Pure and Applied Geophysics》2013,170(4):571-595
To estimate the parameters of ground motion in future strong earthquakes, characteristics of radiation and propagation of seismic waves in the Kamchatka region were studied. Regional parameters of radiation and propagation of seismic waves were estimated by comparing simulations of earthquake records with data recorded by stations of the Kamchatka Strong Motion Network. Acceleration time histories of strong earthquakes (M w = 6.8–7.5, depths 45–55 km) that occurred near the eastern coast of Kamchatka in 1992–1993 were simulated at rock and soil stations located at epicentral distances of 67–195 km. In these calculations, the source spectra and the estimates of frequency-dependent attenuation and geometrical spreading obtained earlier for Kamchatka were used. The local seismic-wave amplification was estimated based on shallow geophysical site investigations and deep crustal seismic explorations, and parameters defining the shapes of the waveforms, the duration, etc. were selected, showing the best-fit to the observations. The estimated parameters of radiation and propagation of seismic waves describe all the studied earthquakes well. Based on the waveforms of the acceleration time histories, models of slip distribution over the fault planes were constructed for the studied earthquakes. Station PET can be considered as a reference rock station having the minimum site effects. The intensity of ground motion at the other studied stations was higher than at PET due to the soil response or other effects, primarily topographic ones. At soil stations INS, AER, and DCH the parameters of soil profiles (homogeneous pyroclastic deposits) were estimated, and nonlinear models of their behavior in the strong motion were constructed. The obtained parameters of radiation and propagation of seismic waves and models of soil behavior can be used for forecasting ground motion in future strong earthquakes in Kamchatka. 相似文献
9.
V. V. Adushkin 《Izvestiya Physics of the Solid Earth》2016,52(2):173-194
The enhancement of seismicity induced by industrial activity in Russia in the conditions of present-day anthropization is noted. In particular, the growth in the intensity and number of strong tectonic earthquakes with magnitudes M ≥ 3 (seismic energy 109 J) due to human activity is revealed. These man-made tectonic earthquakes have started to occur in the regions of the East European Platform which were previously aseismic. The development of such seismicity is noted in the areas of intense long-term mineral extraction due to the increasing production depth and extended mining and production. The mechanisms and generation conditions of man-made tectonic earthquakes in the anthropogenically disturbed medium with the changed geodynamical and fluid regime is discussed. The source zones of these shallow-focus tectonic earthquakes of anthropogenic origin are formed in the setting of stress state rearrangement under anthropogenic loading both near these zones and at a significant distance from them. This distance is determined by the tectonic structure of the rock mass and the character of its energy saturation, in particular, by the level of the formation pressure or pore pressure. These earthquakes occur at any time of the day, have a triggered character, and are frequently accompanied by catastrophic phenomena in the underground mines and on the surface due to the closeness to the source zones. 相似文献
10.
11.
O. V. Pavlenko 《Izvestiya Physics of the Solid Earth》2016,52(3):353-363
The regularities in the radiation and propagation of seismic waves in the regions of the North Caucasus are analyzed for estimating the ground motion parameters during the probable future strong earthquakes. Based on the records of the regional earthquakes with magnitudes MW ~ 3.9–5.6 within epicentral distances up to ~300 km obtained during the period of digital measurements at the Sochi and Anapa seismic stations, the Q-factors in the vicinities of these sites are estimated at ~55 f0.9 and ~90f0.7, respectively. The estimates were obtained by the coda normalization method developed by Aki, Rautian, and other authors. This method is based on the phenomenon of suppression of the earthquake (source) effects and local (site) responses by coda waves in the S-wave spectra. The obtained Q-factor estimates can be used for forecasting the ground shaking parameters for the future probable strong earthquakes in the North Caucasus in the vicinities of Sochi and Anapa. 相似文献
12.
The city of Catania (Italy) in the South-Eastern Sicily has been affected in past times by several destroying earthquakes with high values of estimated magnitude. The seismogenic area to the south of Volcano Etna, known as Iblean Area, is placed between the African and the Euro-Asiatic plates on the west of the Ibleo-Maltese escarpment, to the south of the Graben of the Sicilian channel and on the east of the overlapping front of Gela. Basing on the seismic history of Catania, the following earthquake scenarios have been considered: the “Val di Noto” earthquake of January 11, 1693 (with intensity X-XI on MCS scale, magnitude MW=7.41 and epicentral distance of about 13 km); the “Etna” earthquake of February 20, 1818 (with intensity IX on MCS scale, magnitude MW=6.23 and epicentral distance of about 10 km). The soil response analysis at the surface, in terms of time history and response spectra, has been obtained by 1-D equivalent linear models for about 1200 borings location available in the data-bank of the central area of Catania of about 50 km2, using deterministic design scenario earthquakes as input at the conventional bedrock.Seismic microzoning maps of the city of Catania have been obtained in terms of different peak ground acceleration at the surface and in terms of amplification ratios for given values of frequency. 相似文献
13.
Viewing from the energy angle and taking the Beijing depression as an example, this paper studies the effects of underlying geological structures, mainly bedrock topography and bedrock faults, on the propagation of seismic waves and discusses the effects of the overlying soil layer on seismic waves. From the study, some conclusions are drawn as follows:
- Underlying bedrock faults affect the duration, frequency spectra and characteristics of energy distribution of seismic waves.
- Underlying bedrock topography changes the field of ground motion not only because the bedrock at different places receives different amounts of energy from the same source but also because its asperities diverge or converge seismic waves.
- Overlying soil layer is able both to absorb and to amplify seismic waves.
14.
S. Ruiz E. Kausel J. Campos G. R. Saragoni R. Madariaga 《Pure and Applied Geophysics》2011,168(1-2):125-139
The Chilean subduction zone is one of the most active of the world with M?=?8 or larger interplate thrust earthquakes occurring every 10?years or so on the average. The identification and characterization of pulses propagated from dominant asperities that control the rupture of these earthquakes is an important problem for seismology and especially for seismic hazard assessment since it can reduce the earthquake destructiveness potential. A number of studies of large Chilean earthquakes have revealed that the source time functions of these events are composed of a number of distinct energy arrivals. In this paper, we identify and characterize the high frequency pulses of dominant asperities using near source strong motion records. Two very well recorded interplate earthquakes, the 1985 Central Chile (Ms?=?7.8) and the 2007 Tocopilla (Mw?=?7.7), are considered. In particular, the 2007 Tocopilla earthquake was recorded by a network with absolute time and continuos recording. From the study of these strong motion data it is possible to identify the arrival of large pulses coming from different dominant asperities. The recognition of the key role of dominant asperities in seismic hazard assessment can reduce overestimations due to scattering of attenuation formulas that consider epicentral distance or shortest distance to the fault rather than the asperity distance. The location and number of dominant asperities, their shape, the amplitude and arrival time of pulses can be one of the principal factors influencing Chilean seismic hazard assessment and seismic design. The high frequency pulses identified in this paper have permitted us to extend the range of frequency in which the 1985 Central Chile and 2007 Tocopilla earthquakes were studied. This should allow in the future the introduction of this seismological result in the seismic design of earthquake engineering. 相似文献
15.
四川地区地震动峰值衰减规律研究 总被引：4，自引：1，他引：3
基于四川省地震监测台网27个基岩台站,2008年5月12日——2008年6月10日105次地震（震级ML=4.0——6.4,震中距△=26——623km）的8505条宽频带速度记录,利用实时仿真方法得到了相应的加速度记录,进而对数据进行回归分析,获得了四川地区基岩场地中小地震峰值加速度和峰值速度的衰减关系,并用最近发生的一次4.8级地震对该规律进行了验证．通过四川台网的记录,提出了符合四川地质条件的衰减关系 相似文献
16.
The Sichuan and adjacent areas is divided into southwest China region (SWCR) and Sichuan Basin region (SCBR) according to tectonic backgrounds and seismic damage distribution features. 96 modern destructive earthquakes in SWCR and 40 in SCBR are gathered respectively. All their magnitude parameters are checked. Based on the statis-tic relations between epicentral intensity and magnitude as well as relation between sensible radius and magnitude, the near and far field seismic intensity attenuation features are represented and controlled. And then the seismic intensity attenuation relations along major axis, minor axis and mean axis are established separately. The system-atic deviations of surface wave magnitude between China seismograph network and U.S. seismograph network are considered in this paper. By making use of the new attenuation relations of bedrock horizontal ground acceleration response spectrum in west U.S., the attenuation relations of bedrock horizontal ground acceleration response spec-trum in SWCR and SCBR are digital transformed based on the attenuation model considering acceleration satura-tion of distance and magnitude in near field. 相似文献
17.
K. AfifChaouch B. Tiliouine M. Hammoutene R. Sigbjörnsson R. Rupakhety 《Bulletin of Earthquake Engineering》2016,14(4):1195-1217
Spatial variability of ground motions has significant influence on dynamic response of extended structures such as bridges and tunnels. In this study, the widely used finite-source ground motion simulation approach, the so-called Empirical Green’s Function (EGF) method, is extended to synthesize seismic motions across an array of stations located at bedrock in the epicentral region of the 1980 El-Asnam region (North-West Algeria). The target event being simulated is the October 10 1980 \( M_{s} = 7.2 \) Earthquake, and the EGF is obtained from the ground motion recorded at Sogedia Factory station during the 8 November 1980 \( M_{L} = 5.6 \) aftershock. Coherency functions are then estimated from the simulated ground accelerations. A parametric study investigating the influence of shear wave velocity, earthquake magnitude, and epicentral distance is conducted by simulating ground acceleration for different scenarios using the Hybrid Green’s Function method. The main finding of the study is that finite source effects can cause significant loss in coherency at bedrock in the near-field. In the far-field, the source effect alone does not seem to produce incoherent motion, which implies that scattering and local site effects could be dominating there. Furthermore, coherency functions are found to be more sensitive to inter-station separation in the near-field than in the far-field. Increasing shear wave velocity seems to increase coherency functions, and larger earthquakes seem to produce more incoherent motion than smaller ones. The simulation method presented here produces incoherent motion mainly due to the finite source effect, while path effects are partially accounted for through the EGF, and local site effects are not considered. In this sense, the estimated coherency functions represent that of plane waves. A parametric model of plane wave coherency is calibrated and presented based on the simulation results. The results indicate that the parametric model can be used as a first approximation, and at least an upper bound of lagged coherency in the near-field region of the El-Asnam Earthquake scenario. This model could be useful in random vibration analysis or generation of spatially variable ground motion for time history analysis of lifeline structures in the study area. 相似文献
18.
C. O. Cioflan B. F. Apostol C. L. Moldoveanu G. F. Panza GH. Marmureanu 《Pure and Applied Geophysics》2004,161(5-6):1149-1164
— The mapping of the seismic ground motion in Bucharest, due to the strong Vrancea earthquakes is carried out using a complex hybrid waveform modeling method which combines the modal summation technique, valid for laterally homogeneous anelastic media, with finite-differences technique, and optimizes the advantages of both methods. For recent earthquakes, it is possible to validate the modeling by comparing the synthetic seismograms with the records. We consider for our computations the frequency range from 0.05 to 1.0 Hz and control the synthetic signals against the accelerograms of the Magurele station, low-pass filtered with a cut-off frequency of 1.0 Hz of the 3 last major strong (Mw > 6) Vrancea earthquakes. Using the hybrid method with a double-couple seismic source approximation, scaled for the source dimensions and relatively simple regional (bedrock) and local structure models, we succeeded in reproducing the recorded ground motion in Bucharest at a satisfactory level for seismic engineering. Extending the modeling to the entire territory of the Bucharest area, we construct a new seismic microzonation map, where five different zones are identified by their characteristic response spectra. 相似文献
19.
Andrei Bala Bogdan Grecu Viorica Ciugudean Victor Raileanu 《Soil Dynamics and Earthquake Engineering》2009
Bucharest is one of the cities most affected by earthquakes in Europe. Situated at 150–170 km distance from Vrancea epicentral zone, Bucharest had suffered many damages due to high energy Vrancea intermediate-depth earthquakes. For example, the 4 March 1977 event produced the collapse of 32 buildings with 8–12 levels, while more than 150 old buildings with 6–9 levels were seriously damaged. The studies done after this earthquake had shown the importance of the surface geological structure upon ground motion parameters. New seismic measurements are performed in Bucharest area aiming at defining better elastic and dynamic properties of the shallow sedimentary rocks. Down-hole seismic measurements were performed in a number of 10 cased boreholes drilled in the Bucharest City area. Processing and interpretation of the data lead to the conclusion that shallow sedimentary rocks can be considered weak in the area, down to 150–200 m depth. Seismic wave velocity values and bulk density values presented in the paper associated with local geology are useful primary data in the seismic microzonation of Bucharest City. They are used as 1D models to derive transfer functions and response spectra for the stack of sedimentary rocks in several parts of Bucharest area, leading to a better knowledge of the local site amplification and associated frequency spectra. In a recent study the H/V spectral ratio using Nakamura’s method was applied on the seismic noise measurements in 22 sites in Bucharest City in order to derive the fundamental period associated with these sites. The values confirm the previous results, showing a dominant resonance in the period range of 1.25–1.75 s. The fundamental periods obtained with Nakamura’s method are in good agreement with those computed on the basis of geological and geotechnical data in boreholes, which show an increase of the fundamental period in the Bucharest area from south to north, in the same direction as the increase of the thickness of the Quaternary deposits above the Fratesti layer which is considered the bedrock in the area. 相似文献
20.
This paper presents the attenuation relations of peak ground acceleration and spectral accelerations for rock and soil sites in the central and eastern United States (CEUS). For the bedrock site condition, 56 pairs of moment magnitude M and epicentral distance R are used to simulate ground motion, and for each pair of M and R, 550 samples of ground motion parameters are generated using a seismological model together with random vibration theory and distribution of extreme values. From the regression analyses of these data, the attenuation relations of ground motion parameters for the bedrock site are established. With the aid of appropriate site coefficients, these attenuation relations are modified for the site categories specified in the 1994 NEHRP Provisions. These attenuation relations are appropriate for the assessment of seismic hazards at far-field rock and soil sites in the CEUS. 相似文献