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Haruko Sekiguchi Kojiro Irikura Tomotaka Iwata 《Geophysical Journal International》2002,150(2):377-391
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Simple straightforward methods are applied to testtheir ability to detect the non-linear response of thesoil. Recordings of the main shock and aftershocks ofthe 1995, Hyogo-ken Nanbu (Kobe) earthquake are used.Non-linear effects are investigated using twodifferent techniques, on a collection of data for 12sites situated on different geological structures inthe Kobe and Osaka areas. The first method used is theso-called receiver functions technique (Langston,1979), which consists of computing the spectral ratiobetween horizontal and vertical components of motion.This ratio has been shown to reveal the fundamentalfrequency of a site (Lachet and Bard, 1994; Lachet etal., 1996; Theodulidis et al., 1995, 1996). For eachsite, recordings of the main shock and a set ofaftershocks are considered. The variation of thisspectral ratio for different values of the maximumacceleration recorded at a site is investigated. Bothvariations of the amplitude of the H/V ratio (due tonon-linear behavior, on the horizontal components inparticular) and of the frequency position of theamplified band-width are observed. The secondtechnique used in this study is related to thevariation of the high frequency content of therecordings during the main-shock and its aftershocks.The high frequency spectral decay of the motion,characterized by parameter, is assumed to berelated mainly to the near-surface attenuation. Itshould then increase with increasing peak velocity, incase of non-linearity. The value of kappa iscalculated for the 12 sites in the Kobe area, fordifferent types of soil conditions, and againdifferent values of peak ground acceleration.Variations of kappa are then related to non-linearbehavior of the soil during the Kobe earthquake. 相似文献
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Kojiro?ShimadaEmail author Xiaoyang?Yang Yushi?Araki Ayako?Yoshino Akinori?Takami Xuan?Chen Fan?Meng Shiro?Hatakeyama 《Journal of Atmospheric Chemistry》2018,75(2):123-139
To determine the effects of long-range transport of aerosols from an upwind area in East Asia to a downwind area in Japan, we chemically analyzed aerosols collected simultaneously on Tuoji Island (Shandong Province, China), Fukue Island (Nagasaki Prefecture, Japan), and Cape Hedo (Okinawa Prefecture, Japan). We focused on changes in the metallic composition of PM2.5 aerosols during long-range transport. The average mass concentrations of PM2.5 at the three sites decreased in the order Tuoji Island > Fukue Island ≈ Cape Hedo (48.3 ± 4.5, 13.9 ± 1.5, and 13.2 ± 0.9 μg/m3, respectively). The fraction of coarse particles in total suspended particles estimated by (1–PM2.5/TSP) was highest on Cape Hedo, indicating that the contribution of sea salts was increased by long-range transport of the aerosols over the ocean. Enrichment factor analysis revealed that at all three sites, Al, K, Ca, Mn, Fe, Co, Sr, and Ba originated from soil; whereas Cr, Ni, Cu, Zn, As, Mo, Ag, Cd, Sn, Sb, Tl, and P appeared to be of anthropogenic origin. Na was the most abundant element on Cape Hedo, indicating the addition of sea salts during aerosol transport. The V concentration was highest at Fukue Island, which was ascribed to V emission from ships. Sixty-one percent of the V on Fukue Island and 62% of the V on Cape Hedo were determined to have originated from ships, implicating of data obtained on dates during which backward trajectory analysis indicated that the same air mass passed over Tuoji Island, Fukue Island, and Cape Hedo in that order. 相似文献
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Records of the Niigata Chuetsu-Oki earthquake (July, 16, 2007, M w?=?6.6, depth ~17?km) and its aftershocks from seismic vertical arrays deployed at the territory of the Kashiwazaki-Kariwa nuclear power plant (~15?km from the fault) are used to study the soil behavior down to ~250?m during strong ground motion. Nonlinear models of soil behavior during the main shock and six aftershocks are constructed, and stresses and strains induced by the strong motion in the soil layers at various depths are estimated. The data are processed using the method developed by Pavlenko and Irikura (Bull Seismol Soc Am 96(6): 2131–2145, 2003) and previously applied for studying the soil behavior in near-fault zones during the 1995 Kobe and 2000 Tottori earthquakes. A rather good agreement between the recorded and simulated acceleration time histories testifies to the validity of the obtained vertical distributions of stresses and strains in soil layers. In the upper, softer layers (~45?m) at the territory of the plant, the shear moduli were reduced by ~30–35% during the main shock and by ~1.5–3% during the aftershocks. The constructed models of soil behavior can be used in scenario earthquake shaking maps of Japan where, based on source modeling parameters, the level of strong motion can be evaluated for the territory of the power plant in future earthquakes with various magnitudes and fault planes. Using methods of stochastic finite-fault modeling of ground motions from the Chuetsu-Oki earthquake, we estimated input motion to the soil layers during the main shock and found that it differs from the imposed motion (recorded by the deepest sensor of the vertical array) by slightly decreased (by a factor of ~1.2) low-frequency (f?<?10?Hz) spectral components. 相似文献
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We investigate a special type of variability in response spectral amplification ratios computed from numerical “engineering” models for a soft soil site. The engineering models are defined by shallow soil layers over “engineering” bedrock with a shear-wave velocity over 600–700 m/s and the model is subjected to vertical propagating shear waves. The variability, perhaps unique in earthquake engineering, is a result of the “perfectly accurate” computational procedure. For example, an engineering soil site model, subjected to two rock site records or the two horizontal components of a rock site record, produces different response spectral amplification ratios. We use a large number of strong-motion records from “engineering” rock sites, with a reasonably balanced distribution with respect to magnitude and source distance, generated by subduction earthquakes in Japan, to investigate the nature of the variability. In order to avoid any approximation in removing the effect of soil nonlinear response, we use a simple model, a single horizontal soil layer over a bedrock, modelled as elastic. We then demonstrate that a similar type of variability observed in the one- or two-dimensional nonlinear soil models is caused by the nature of response spectral amplification ratios, not a direct result of soil nonlinear response. Examination of variability reveals that the average of response spectral amplification ratios systematically depends on both earthquake magnitude and source distance. We find that, at periods much longer than the site natural periods of the soil sites, the scatter of the amplification ratios decreases with increasing magnitude and source distance. These findings may have a potential impact in establishing design spectra for soft soil sites using strong-motion attenuation models or dynamic numerical modelling. 相似文献
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Prediction of strong ground motion at EURO-SEISTEST site using the empirical Green's function method
This paper presents some tests on the empirical Green's function method, performed in order to check its effectiveness to predict strong ground motion during future large earthquakes. These investigations basically consist of blind or pseudo-blind tests using part of the data set obtained at the Volvi (Greece) test-site within the framework of the EURO-SEISTEST project. In a first step, a moderate event (ML=4.1) is simulated by using a small event (ML=2.5), and taking into account the a priori knowledge of the relevant source parameters (magnitude and stress-drop) for both the base and target events. This check emphasizes the sensitivity of the prediction to the stress-drop values. In a second step, a pseudo-blind prediction is carried out in which the information on the target event is only the magnitude (ML=5.3) besides the geometrical parameters such as source location, strike and dip. The other important parameters (seismic moment, fault area, stress-drop) are determined on the basis of specific empirical scaling laws derived from several small and moderate events occurring in the area. The synthetic motions are computed for two nearby sites, which are located on the southern edge and in the center of the Mygdonian graben, respectively, and correspond to much different site conditions: weathered rock and thick sediments. They are found in good agreement with the observations, which were unveiled after the simulation. In particular, the amplitude and the phase of the late, local surface waves generated on the southern edge of the graben, are very well reproduced at valley center. Finally, the last step is an attempt to predict strong ground motion for a hypothetical large earthquake of magnitude ML=6.5. The results are shown to depend very significantly on the scaling laws. 相似文献
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We developed a recipe for predicting strong ground motions based on a characterization of the source model for future crustal earthquakes. From recent developments of waveform inversion of strong motion data used to estimate the rupture process, we have inferred that strong ground motion is primarily related to the slip heterogeneity inside the source rather than average slip in the entire rupture area. Asperities are characterized as regions that have large slip relative to the average slip on the rupture area. The asperity areas, as well as the total rupture area, scale with seismic moment. We determined that the areas of strong motion generation approximately coincide with the asperity areas. Based on the scaling relationships, the deductive source model for the prediction of strong ground motions is characterized by three kinds of parameters: outer, inner, and extra fault parameters. The outer fault parameters are defined as entire rupture area and total seismic moment. The inner fault parameters are defined as slip heterogeneity inside the source, area of asperities, and stress drop on each asperity based on the multiple-asperity model. The pattern of rupture nucleation and termination are the extra fault parameters that are related to geomorphology of active faults. We have examined the validity of the earthquake sources constructed by our recipe by comparing simulated and observed ground motions from recent inland crustal earthquakes, such as the 1995 Kobe and 2005 Fukuoka earthquakes. 相似文献
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Estimation of Nonlinear Time-dependent Soil Behavior in Strong Ground Motion Based on Vertical Array Data 总被引：2，自引：0，他引：2
To improve our understanding of nonlinear elastic properties of soils, a method is proposed of estimation of stress-strain relations of soils in situ in strong ground motion based on vertical array data. Strong motion records provided by seismic vertical arrays allow estimation of nonlinear stress-strain relations in soil layers at different depths, from the surface down to the location of the deepest device. As an example, records obtained during the main shock of the 1995 Kobe earthquake at Port-Island, SGK, and TKS sites were used to estimate the stress-strain relations in the soil profiles. For different layers, different types of nonlinear stress-strain relations were selected, according to the profiling data. To account for temporal changes in the soil behavior, consecutive parts of records were examined, and for successive time intervals, the relations were found showing the best-fit approximation to the observed data. At Port Island and SGK sites, where the strongest accelerations were recorded, the obtained stress-strain relations showed systematic changes in the upper layers (0–14 m), such as, a progressive reduction of the slopes of the stress-strain curves due to liquefaction at Port Island and reduction and recovery of the slopes at SGK and TKS sites. At the three sites, the stress-strain relations remained stable in layers below 11–14 m. Thus, the proposed approach gives us a representation of the soil behavior in layers at different depths in strong ground motion; it allows calculation of the propagation of arbitrary seismic signals in the studied profiles and estimation of nonlinear components in the ground response by the nonlinear system identification technique. The method can also be applied to evaluate the ground response at sites where profiling data are available and an imposed motion can be estimated. 相似文献