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Satoh?ToshimiEmail author Hiroshi?Kawase Tomotaka?Iwata Sadanori?Higashi Sato?Toshiaki Huey-Chu?Huang 《Journal of Seismology》2004,8(4):545-558
The 1999 Chi-Chi, Taiwan earthquake, MW = 7.6, caused severe damage in the near-fault region of the earthquake. In order to evaluate site effects in the near-field strong motions we estimate S-wave velocity structures of sediments at four sites using array records of microtremors. We also recalculated S-wave velocity structures at other four sites previously reported. To show the validity of the estimated S-wave velocity structures we separate empirical site responses from aftershock records using the generalized inversion method and show the agreement between empirical and theoretical site responses. We also show an observed fact that suggests soil nonlinearity during the Chi-Chi earthquake by comparing horizontal-to-vertical spectral ratios (HVRs) for main shock records with HVRs for aftershock records. Then we calculate one-dimensional equivalent-linear site responses using the estimated S-wave velocity structures and the main shock records observed on the surface. It is found that site amplification due to thick (about 6 km) sediments is one of the important factors for explaining the long-period velocity pulses of about 5 to 10 sec observed at sites in the footwall during the Chi-Chi earthquake. It is also found that the theoretical site responses of shallow soft sediments at sites that sustained severe damage in the hanging wall shows significant amplification around 1 sec. As the amplitude of velocity pulses with period around 1 sec is most critical in causing damage to ordinary buildings of moderate heights, our results suggest that the 1-sec period velocity pulses, amplified by the site response of shallow sediments should contribute to the severe damage during the Chi-Chi earthquake. 相似文献
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Climate Dynamics - Rain-on-Snow (ROS) events can cause severe snowmelt hazards such as river flooding, avalanches, and landslides that have significant impacts on various sectors. The influence of... 相似文献
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Molnar S. Sirohey A. Assaf J. Bard P.-Y. Castellaro S. Cornou C. Cox B. Guillier B. Hassani B. Kawase H. Matsushima S. Sánchez-Sesma F. J. Yong A. 《Journal of Seismology》2022,26(4):653-685
Journal of Seismology - The single-station microtremor horizontal-to-vertical spectral ratio (MHVSR) method was initially proposed to retrieve the site amplification function and its resonance... 相似文献
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Ziqian Wang Kenichi Nakano Eri Ito Hiroshi Kawase Shinichi Matsushima 《地震工程与结构动力学》2023,52(1):128-146
Under hypothetical and idealized conditions, the horizontal site amplification factor (HSAF) is defined as the ratio of the horizontal Fourier amplitude spectrum (FAS) at a point on the Earth's surface with respect to the horizontal FAS at the identical location but on the outcropping seismological bedrock. The HSAF reflects the profile of local sedimentary soils and weathered rock formations, indicating site effects. In most cases, such an idealized HSAF is difficult to measure directly. Thus, quantitatively estimating a HSAF value is a crucial task in strong-motion prediction over the last century. Fortunately, many strong-motion stations have been constructed throughout Japan, facilitating the characterization of HSAFs down to seismological bedrock at more than 1600 observational sites by the generalized inversion technique (GIT). First, this study reported the similarity distribution of the HSAF and the horizontal-to-vertical spectral ratio of earthquakes (HVSRE). Subsequently, we proposed a hybrid method from a novel aspect for estimating HSAF in terms of the observed similarity distribution and the vertical amplification correction function (VACF) proposed previously. Compared with the direct use of HVSRE for substituting HSAF, the hybrid method proposed herein demonstrated an improvement of greater than 30% in terms of the residuals between estimated HSAFs and those separated from observations. 相似文献
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Kiyoshi Fujimoto Kumiko Kawase Shigehiro Ishizuka Koji Shichi Akio Ohira Hiroshi Adachi 《Quaternary Science Reviews》2009,28(15-16):1472-1480
We estimated stored sediment and carbon during the Holocene for each layer of the Yahagi River Delta, central Japan and discussed the provenance of stored carbon. To estimate the bulk density and the carbon content of each layer, we collected two 30 m deep undisturbed cores. The volume of each layer was calculated using ArcView 3D analyst. Although the volume ratio of each layer to the total volume was calculated to be 9.5% for the top mud layer, 34.9% for the upper sand layer, 32.8% for the middle mud layer and 22.9% for the lower sand layer, the mass ratio of each layer to the total mass was calculated to be 8.5, 40.9, 25.2 and 25.4%, respectively, and the stored carbon ratio in each layer to the total stored carbon was 20.4, 4.7, 55.9 and 18.9%, respectively. These results suggest that the top mud and middle mud layers have a significant role as a place for carbon sequestration during postglacial time. Total stored carbon in the study area of only 92.1 km2 was estimated at 26 Tg C, which is equivalent to 0.003% of atmospheric carbon. This suggests that deltas on the globe have accumulated a massive amount of carbon during the evolution. The inorganic carbon ratio to total carbon reached more than 45% around the boundary between the middle mud and lower sand layers. The increasing trend in the Corg/Ntotal ratio accompanied with a decrease in δ13C from the bottom to the top horizon in the middle mud layer indicates a gradual increase in terrestrial organic matter contribution. The relative proportion of terrestrially derived materials decreases with increasing distance seaward. 相似文献
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The relatively slow flow and exchange of Carr Inlet water with the main basin of Puget Sound, Washington, favor eutrophication.
To study Carr Inlet’s circulation, the Model-measurement Integration Experiment in Estuary Dynamics (MIXED) was conducted
in March–May 2003, spanning the spring bloom. From observations and numerical simulations the circulation was decomposed into
tidal and subtidal components; the former was dominated by the M2 tide, the latter by atmospheric forcing. Near the surface,
the subtidal velocity was correlated with wind. At mid depths, the subtidal velocity was organized into vertical bands arising
from internal waves excited by wind forcing of the water surface. The tidal flow was more strongly steered by local bathymetry
and weaker in peak magnitudes than the subtidal flow, yet it contributed more mechanical energy to the inlet. Tidal eddies
reduce exchange of water through the inlet’s entrances. Numerical simulations with the Princeton Ocean Model recreated many
observed features, including the three-layer vertical structure of outflow at the surface and bottom and inflow at mid depth,
the mid-depth subtidal response to the wind, and characteristics of the tide. While the model produced greater subtidal flow
magnitudes at depth and differences in the phase of the M2 tide compared to observations, overall the case study provided
support for more comprehensive simulations of Puget Sound in the future. 相似文献
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Stephanie K. Moore Nathan J. Mantua Jan A. Newton Mitsuhiro Kawase Mark J. Warner Jonathan P. Kellogg 《Estuarine, Coastal and Shelf Science》2008,80(4):545-554
Temporal and spatial patterns of variability in Puget Sound's oceanographic properties are determined using continuous vertical profile data from two long-term monitoring programs; monthly observations at 16 stations from 1993 to 2002, and biannual observations at 40 stations from 1998 to 2003. Climatological monthly means of temperature, salinity, and density reveal strong seasonal patterns. Water temperatures are generally warmest (coolest) in September (February), with stations in shallow finger inlets away from mixing zones displaying the largest temperature ranges. Salinities and densities are strongly influenced by freshwater inflows from major rivers during winter and spring from precipitation and snowmelt, respectively, and variations are greatest in the surface waters and at stations closest to river mouths. Vertical density gradients are primarily determined by salinity variations in the surface layer, with stations closest to river mouths most frequently displaying the largest buoyancy frequencies at depths of approximately 4–6 m. Strong tidal stirring and reflux over sills at the entrance to Puget Sound generally removes vertical stratification. Mean summer and winter values of oceanographic properties reveal patterns of spatial connectivity in Puget Sound's three main basins; Whidbey Basin, Hood Canal, and Main Basin. Surface waters that are warmed in the summer are vertically mixed over the sill at Admiralty Inlet and advected at depth into Whidbey Basin and Hood Canal. Cooler and fresher surface waters cap these warmer waters during winter, producing temperature inversions. 相似文献