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31.
Properties of seismoelectric waves in relation to natural earthquakes have been investigated. The electromagnetic disturbances were analyzed to test the hypothesis that pulse-like electric variations are directly related to microcracks as source. Because variation is very difficult to detect, there have been few quantitative field investigations. We used selected events with clear S and P phases from the data catalog obtained before the Tohoku earthquake in 2011. The electric strength of the fast P wave (Pf), S wave (S), and electromagnetic wave (EM) associated with formation of cracks of tensile mode were estimated. The co-seismic electric signal accompanied by the S wave has the largest strength, well above the noise level, and the EM wave has the lowest strength. Analytical estimation of the ratio of the strengths of the Pf and EM phases to that of the S phase by use of Pride’s equations gave results partially in agreement with observation (the order was Apf > As > Aem). The strength of the observed electromagnetic mode is approximately two orders of magnitude larger than that estimated from the theory. We suggest this greater strength can be attributed to the converted modes at layer contracts or to the effect of the boundary between free atmosphere and crust. Overall agreement between observations and theoretical estimates suggests that electromagnetic anomalies, crustal deformation, and groundwater changes can be investigated on the basis of the unified equations for the coupled electromagnetics, acoustics, and hydrodynamics of porous media. 相似文献
32.
Assessing flood disaster impacts in agriculture under climate change in the river basins of Southeast Asia 总被引:1,自引:0,他引:1
Shrestha Badri Bhakta Perera Edangodage Duminda Pradeep Kudo Shun Miyamoto Mamoru Yamazaki Yusuke Kuribayashi Daisuke Sawano Hisaya Sayama Takahiro Magome Jun Hasegawa Akira Ushiyama Tomoki Iwami Yoichi Tokunaga Yoshio 《Natural Hazards》2019,97(1):157-192
Natural Hazards - This study focused on flood damage assessment for future floods under the impact of climate change. Four river basins of Southeast Asia were selected for the study. They included... 相似文献
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34.
Yoshifumi Nogi Kumiko Nishi Nobukazu Seama Yoichi Fukuda 《Marine Geophysical Researches》2004,25(3-4):221-231
The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We
summarize the structural lineaments deduced from the GEOSAT 10 Hz sampled raw altimetry data as well as satellite derived
gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the
Southern Indian Ocean. The gravity anomaly maps by both Sandwell and Smith 1997, J. Geophys. Res. 102, 10039–10054 and 10 Hz raw altimeter data show almost the same general trends. However, curved structural trends, which turn
from NNW–SSE in the south to NNE–SSW in the north, are detected only from gravity anomaly maps by 10 Hz raw altimeter data
just to the east of Gunnerus Ridge. NNE–SSW structural trends and magnetic anomaly lineation trends that are perpendicular
to them are observed between the Gunnerus Ridge and the Conrad Rise. To the west of Gunnerus Ridge, structural elements trend
NNE–SSW and magnetic polarity changes are normal to them. In contrast, almost NNW–SSE structural trends and ENE–WSW magnetic
polarity reversal strikes are dominant to the east of Gunnerus Ridge. Curved structural trends, which turn from WNW–ESE direction
in the south to NNE–SSW direction in the west, and magnetic polarity reversal strikes that are almost perpendicular to them
are observed just south of Conrad Rise. The magnetic polarity reversals may be parts of the Mesozoic magnetic anomaly sequence
that formed along side of the structural lineaments before the long Cretaceous normal polarity superchron. Curved structural
trends, detected only from gravity anomaly maps by 10 Hz raw altimeter data, most likely indicate slight changes in spreading
direction from an initial NNW–SSE direction to NNE–SSW. Our results also suggest that these curved structural trends are fracture
zones that formed during initial breakup of Gondwana. 相似文献
35.
Wells turbine with end plates for wave energy conversion 总被引:1,自引:0,他引:1
Manabu Takao Toshiaki Setoguchi Yoichi Kinoue Kenji Kaneko 《Ocean Engineering》2007,34(11-12):1790-1795
In order to improve the performance of the Wells turbine for wave energy conversion, the effect of end plate on the turbine characteristics has been investigated experimentally by model testing. As a result, it is found that the characteristics of the Wells turbine with end plates are superior to those of the original Wells turbine, i.e., the turbine without end plate and the characteristics are dependent on the size and position of end plate. Furthermore, by using a computational fluid dynamics (CFD), reason of the performance improvement of the turbine has been clarified and the effectiveness of the end plate has been demonstrated. 相似文献
36.
A storage-efficient reconstruction framework for cartographic planar contours is developed. With a smaller number of control points, we aim to calculate the area and perimeter as well as to reconstruct a smooth curve. The input data forms an oriented contour, each control point of which consists of three values: the Cartesian coordinates (x, y) and tangent angle θ. Two types of interpolation methods are developed, one of which is based on an arc spline while the other one is on a cubic Hermite spline. The arc spline-based method reconstructs a G1 continuous curve, with which the exact area and perimeter can be calculated. The benefit of using the Hermite spline-based method is that it can achieve G2 continuity on most control points and can obtain the exact area, whereas the resulting perimeter is approximate. In a numerical experiment for analytically defined curves, more accurate computation of the area and perimeter was achieved with a smaller number of control points. In another experiment using a digital elevation model data, the reconstructed contours were smoother than those by a conventional method. 相似文献
37.
38.
Hasanuddin Z. Abidin Heri Andreas Irwan Gumilar Yoichi Fukuda Yusuf E. Pohan T. Deguchi 《Natural Hazards》2011,59(3):1753-1771
Jakarta is the capital city of Indonesia with a population of about 9.6 million people, inhabiting an area of about 660 square-km.
In the last three decades, urban development of Jakarta has grown very rapidly in the sectors of industry, trade, transportation,
real estate, and many others. This exponentially increased urban development introduces several environmental problems. Land
subsidence is one of them. The resulted land subsidence will also then affect the urban development plan and process. It has
been reported for many years that several places in Jakarta are subsiding at different rates. The leveling surveys, GPS survey
methods, and InSAR measurements have been used to study land subsidence in Jakarta, over the period of 1982–2010. In general,
it was found that the land subsidence exhibits spatial and temporal variations, with the rates of about 1–15 cm/year. A few
locations can have the subsidence rates up to about 20–28 cm/year. There are four different types of land subsidence that
can be expected to occur in the Jakarta basin, namely: subsidence due to groundwater extraction, subsidence induced by the
load of constructions (i.e., settlement of high compressibility soil), subsidence caused by natural consolidation of alluvial
soil, and tectonic subsidence. It was found that the spatial and temporal variations of land subsidence depend on the corresponding
variations of groundwater extraction, coupled with the characteristics of sedimentary layers and building loads above it.
In general, there is strong relation between land subsidence and urban development activities in Jakarta. 相似文献
39.
40.
Equivalent widths and line widths of Ca II infrared triplet emission lines were measured in the high-resolution optical spectra of 39 young stellar objects.We found that the equivalent widths of the emission lines decrease with stellar evolution.It has often been claimed that strong chromospheric activity is generated by a dynamo process caused by fast rotation of the photosphere.However,we found no clear correlation between the strength of the Ca II lines and the stellar rotation velocity.Instead,we found that the objects with high mass accretion rates had stronger Ca II emission lines.This correlation supports the turbulent chromosphere model or the magnetic accretion theory for classical T Tauri stars.We also noticed that the equivalent widths of Ca II lines in transitional disk objects are one-tenth of those in classical T Tauri stars,even if the masses of the circumstellar disks are comparable. 相似文献