基于格网数据的洪水灾害风险评估方法——以日本新川洪灾为例

本文对日本格网统计数据的历史、体系以及结构进行了介绍 ,并应用地理信息技术给出了各级格网的自动生成方法。同时以 2 0 0 0年日本新川洪水灾害为案例 ,建立了二维洪水演进水动力学模型 ,并采用地理信息系统与水动力学模型结合的方法对新川破堤洪水泛滥进行了模拟 ,同时对洪泛区灾害损失进行了评估 ,得到的结果为进一步评估洪水灾害风险以及确定合理的洪灾保险费率奠定了基础 ,对于格网统计数据在城市规划以及城市减灾等领域的应用也有一定的借鉴意义。     

Evaluation of the resistance of coastal Pinus thunbergii Parlat. forests to the tsunami fluid force in Japan

Natural Hazards - Coastal forests can protect coastal areas from the effects of tsunamis. However, the coastal forests of Tohoku were destroyed by the Great East Japan Tsunami, which was triggered...     

Current state of integrated earthquake simulation for earthquake hazard and disaster

This paper presents the current state of integrated simulation for earthquake hazard and disaster. This simulation takes advantage of the macro–micro analysis method; this method estimates an earthquake’s strong motion with high spatial and temporal resolution, using the bounding medium theory to obtain optimistic and pessimistic estimates of expected strong motion distribution and the singular perturbation expansion that results in an efficient multi-scale analysis. Integrated earthquake simulation calculates seismic responses for all structures in a target area, inputting simulated strong ground motion to a structure analysis method that is plugged into the system by means of a wrapper; a suitable method, linear or nonlinear, is chosen depending on the type of the structure. The results of all simulations are visualized so that residences and government officials can share a common recognition of earthquake hazard and disaster. Two examples of this integrated earthquake simulations are presented; one is made by plugging nonlinear structure analysis methods into the system, and the other is made for an actual city, the computer model of which is constructed with the help of available geographical information systems.     

Radio Bursts Associated with Flare and Ejecta in the 13 July 2004 Event

We investigate coronal transients associated with a GOES M6.7 class flare and a coronal mass ejection (CME) on 13 July 2004. During the rising phase of the flare, a filament eruption, loop expansion, a Moreton wave, and an ejecta were observed. An EIT wave was detected later on. The main features in the radio dynamic spectrum were a frequency-drifting continuum and two type II bursts. Our analysis shows that if the first type II burst was formed in the low corona, the burst heights and speed are close to the projected distances and speed of the Moreton wave (a chromospheric shock wave signature). The frequency-drifting radio continuum, starting above 1 GHz, was formed almost two minutes prior to any shock features becoming visible, and a fast-expanding piston (visible as the continuum) could have launched another shock wave. A possible scenario is that a flare blast overtook the earlier transient and ignited the first type II burst. The second type II burst may have been formed by the same shock, but only if the shock was propagating at a constant speed. This interpretation also requires that the shock-producing regions were located at different parts of the propagating structure or that the shock was passing through regions with highly different atmospheric densities. This complex event, with a multitude of radio features and transients at other wavelengths, presents evidence for both blast-wave-related and CME-related radio emissions.     

Two modes of climatic control in the Holocene stalagmite record from the Japan Sea side of the Japanese islands

The Holocene stalagmite FG01 collected at the Fukugaguchi Cave in Itoigawa, central Japan provides a unique high‐resolution record of the East Asian winter monsoon. Because of the climate conditions on the Japan Sea side of the Japanese islands, the volume of precipitation during the winter is strongly reflected in the stalagmite δ¹⁸O signal. Examination of the carbon isotopes and the Mg/Ca ratio of FG01 provided additional information on the Holocene climate in Itoigawa, which is characterized by two different modes separated at 6.4 ka. Dripwater composition and the correlation between the δ¹³C and Mg/Ca data of FG01 indicate the importance of prior calcite precipitation (PCP), a process that selectively eliminated ¹²C and calcium ions from infiltrating water from CO₂ degassing and calcite precipitation. In an earlier period (10.0–6.4 ka), an increase in soil pCO₂ associated with warming and wetting climate trends was a critical factor that enhanced PCP, and resulted in an increasing trend in the Mg/Ca and δ¹³C data and a negative correlation between the δ¹³C and δ¹⁸O profiles. A distinct peak in the δ¹³C age profile at 6.8 ka could be a response to an increase of approximately 10% in C4 plants in the recharge area. At 6.4 ka, the climate mode changed to another, and correlation between δ¹⁸O and δ¹³C became positive. In addition, a millennial‐scale variation in δ¹⁸O and pulsed changes in δ¹³C and Mg/Ca became distinct. Assuming that δ¹⁸O and PCP were controlled by moisture in the later period, the volume of precipitation was high during 6.0–5.2, 4.4–4.0, and 3.0–2.0 ka. In contrast, the driest interval in Itoigawa was during 0.2–0.4 ka, and broadly corresponds to the Little Ice Age.     

Study on the Historical Distribution of Metals in Aquatic Sediments

In this study, the historical distribution of metals, phosphorous, and sulfur at four different depths in the sediments of different lakes formed in the course of an urban river (in Londrina, Parana State, Brazil) were determined. The transport of metals along the course of the river was observed mainly for Mn, Cr, and Zn. High concentrations of Pb in the Capivara Bay and Cr in the river were attributed to contamination from a battery plant and a tannery, respectively. The concentrations of heavy metals in the deepest layers of the sediments remain high several years after deposition.     

Physical criterion to evaluate seismic activity associated with the seismic cycle of great interplate earthquakes

A new criterion is introduced to judge if the vicinity of the source region of a great interplate earthquake is in an active period. It is based on the stress change caused by the great earthquake. A region is regarded as being in an active period of seismicity if the occurrence rate of earthquakes on faults in the stress shadow of the great earthquake is significantly higher than in the early stage of the seismic cycle, and if the stressing rate of these faults is sufficiently low. This criterion was applied to the seismicity in the central part of southwest Japan before and after the 1944 Tonankai and 1946 Nankai earthquakes. The results show that before the 1944 Tonankai earthquake, the region was in an active period from at least 1927.The region was in a quiet period for almost50 years after the 1946 Nankai earthquake.Data after 1995 show that the region is once more in an active period of seismicity preceding the next great interplate earthquakes along the Nankai trough,although the total number of earthquakes has not yet significantly increased. Our results indicate that earthquake probability in the central part of southwest Japan will become high in the coming decades until the next great interplate earthquakes along the Nankai trough.