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1.
采用球坐标系下非线性浅水波方程, 研究日本本州M9.0大地震引发的海啸对中国东南沿海的影响, 并计算了冲绳海槽构造带上3个不同段落可能发生潜在地震引发的海啸, 分析这些海啸与日本大海啸的浪高和走时关系. 结果表明, 日本地震海啸模拟结果与日本当地报道及中国东南沿海7个验潮站的报道结果相符. 冲绳海槽构造带中段可能发生的3次不同震级（M7.0, M7.5, M8.0）潜在地震引发的海啸到达中国东南沿海的时间比日本海啸提前约4个小时, 从震源区传播3个多小时即可到达华东沿海部分验潮站. 冲绳海槽M7.5潜在地震海啸在验潮站上计算的波高与日本海啸相当, 中冲绳海槽M8.0潜在地震海啸在大陈站的波高将超过0.9 m, 在坎门站波高将超过1.8 m. 北冲绳海槽的潜在地震海啸威胁主要集中在江苏盐城、 上海一带, 南冲绳海啸主要对台湾东北部和浙江沿海产生威胁. 本文对冲绳海槽构造带上潜在地震引发海啸的模拟结果, 可为中国东南沿海地区的防震减灾、 海啸预警提供有意义的参考. 相似文献
2.
我国地震海啸危险性分析方法研究 总被引：4，自引：0，他引：4
美国、日本等国家已经建立了完善的海啸防灾减灾机制，对海啸危险性分析方法的研究也做了很多的工作，而我国目前在这方面尚属空白。本文首次对我国的海啸危险性分析方法进行了研究，提出了我国地震海啸危险性分析的基本原则，在此基础上，借鉴我国成熟的地震危险性分析方法，建立了我国地震海啸危险性分析方法的主要步骤。在根据我国一些历史地震海啸资料的基础上，通过统计的方法对我国珠江三角洲的海啸危险性进行了研究。 相似文献
3.
Effects of bathymetry on tsunami propagation: Application of ray tracing to tsunamis 总被引：4，自引：0，他引：4
Kenji Satake 《Pure and Applied Geophysics》1988,126(1):27-36
Ray tracing of seismic surface waves is applied to tsunami propagation to examine bathymetric effect along its propagation path. Computations are made for trans-Pacific tsunamis and for near-field tsunamis in the Japan Sea. For tsunamis across the Pacific Ocean, the comparison to a uniform ocean shows that focusing and defocusing, due to bathymetry, are significant for some combinations of source and receiver. For example, the refraction of rays is predominant at the East Pacific Rise for the tsunami from Chile. The tsunamis in the Japan Sea are strongly affected by the shallow Yamato Rise. The predicted arrival time and amplitude distribution generally agree with the observations from an actual tsunami. Since the computation can be made very quickly, the method is useful for preliminary analysis of tsunami propagation, such as in an operational warning system or in the determination of computational area for finite-difference computation. 相似文献
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Seasonal variation of upper layer circulation in the northern part of the East/Japan Sea and its mechanism were investigated using empirical orthogonal function (EOF) analysis with satellite sea surface heights over the northern East/Japan Sea and a three-dimensional circulation model. The spatial structure and temporal variation of first EOF mode, which explains about 64% of the total variance, indicate that a large cyclonic circulation in the northern East/Japan Sea shows a semi-annual variation with maximum strength in summer and winter. According to numerical model result, the Liman Cold Current, accepted as a major current in the northern East/Japan Sea, is well mixed vertically by the winter monsoon and the current in the upper layer has a relatively deep structure, with a maximum westward speed of about 20 cm/s in winter. On the other hand, in summer the current has a stronger baroclinic structure of velocity than in winter. Numerical experiments showed that in summer the temporal variation of upper layer circulation is controlled by thermal forcing, such as sea surface heat flux and inflow of heat transport into the East/Japan Sea through the Korea/Tsushima Strait. Moreover, the cyclonic circulation in the upper layer of the northern East/Japan Sea is also generated and strengthened by the positive wind stress curl occupying most of the East/Japan Sea during the winter. The seasonal variation of each forcing that drives the circulation is responsible for the strength or weakness of the upper layer circulation in the northern East/Japan Sea. The contribution of each forcing to the seasonal variation of the upper layer circulation is examined through sensitivity experiments. According to these numerical experiments, the upper layer circulation in the northern East/Japan Sea is strengthened twice a year, in winter and summer, and this semi-annual variation is determined by a combination of wind (winter) and thermal (summer) forcing. 相似文献
6.
Geochemical characteristics of deposits from the 2011 Tohoku‐oki tsunami at Hasunuma,Kujukuri coastal plain,Japan 
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下载免费PDF全文 Tetsuya Shinozaki Yuki Sawai Junko Hara Minoru Ikehara Dan Matsumoto Koichiro Tanigawa 《Island Arc》2016,25(5):350-368
We examined the geochemical characteristics and temporal changes of deposits associated with the 2011 Tohoku‐oki tsunami. Stable carbon isotope ratios, biomarkers, and water‐leachable ions were measured in a sandy tsunami deposit and associated soils sampled at Hasunuma, Kujukuri coastal plain, Japan, in 2011 and 2014. At this site, the 2011 tsunami formed a 10–30 cm ‐thick layer of very fine to medium sand. The tsunami deposit was organic‐poor, and no samples contained any detectable biomarkers of either terrigenous or marine origin. In the underlying soil, we identified hydrocarbons and sterols derived from terrestrial plants, but detected no biomarkers of marine origin. In the samples collected in 2011, concentrations of tsunami‐derived water‐leachable ions were highest in the soil immediately beneath the tsunami deposit and then decreased gradually with depth. Because of its finer texture and higher organic content, the soil has a higher water‐holding capacity than the sandy tsunami deposit. This distribution suggests that ions derived from the tsunami quickly penetrated the sand layer and became concentrated in the underlying soil. In the samples collected in 2014, concentrations of water‐leachable ions were very low in both soil and sand. We attribute the decrease in ion concentrations to post‐tsunami rainfall, seepage, and seasonal changes in groundwater level. Although water‐leachable ions derived from seawater were concentrated in the soil beneath the tsunami deposit following the tsunami inundation, they were not retained for more than a few years. To elucidate the behavior of geochemical characteristics associated with tsunamis, further research on organic‐rich muddy deposits (muddy tsunami deposits and soils beneath sandy tsunami deposits) as well as sandy tsunami deposits is required. 相似文献
7.
Numerical identification of tsunami boulders and estimation of local tsunami size at Ibaruma reef of Ishigaki Island,Japan 下载免费PDF全文
下载免费PDF全文 Tsunami boulders deposited along the coast constitute important geological evidence for paleotsunami activity. However, boulders can also be deposited by large storm waves. Although several sedimentological and theoretical methods have been proposed to differentiate tsunami and storm wave affected boulders, no appropriate numerical method exists for their differentiation. Therefore, we developed a new numerical scheme to differentiate tsunami and storm wave boulders for coastal boulders on Ishigaki Island, Japan. In this area, tsunami and storm waves have emplaced numerous boulders on the reef and the coast. By conducting numerical calculations of storm waves in this region, we estimated the size of a storm wave that can explain the maximum clast size distribution of boulders on the reef. Consequently, we showed that a wave with a combination of 8 m in initial wave height and 10 s period can satisfy the above conditions when we assume mean sea level. In contrast to the boulders on the reef, all boulders deposited along the shore are heavier than the calculated possible maximum clast size distribution by the storm wave. Therefore, we confirmed these boulders as being of tsunami origin. Results of previous studies showed that they were most likely deposited or reworked by the 1771 Meiwa tsunami. Then, using the tsunami boulders, we numerically estimated the wave period and amplitude of the 1771 Meiwa tsunami, which should have had a 4–5 min period and 5.6–5.9, 6.3–7.0 m amplitude, respectively. Using the proposed scheme, it is possible to differentiate tsunami and storm wave boulders and estimate the size of past storm waves and tsunami waves, although it is noteworthy that there are exceptions for which the scheme cannot be applied. 相似文献
8.
A source model was discussed for a small tsunami accompanied by the Noto-Hanto-Oki earthquake (M
s
6.6), striking Japan on 7 February, 1994. Assuming a fault model under the sea bottom, we estimated the focal parameters jointly, using synthesized tsunami source spectra as well as the tsunami numerical simulation. The fault proposed by this study consists of a plane sized 15×15 km, dipping N47°W with the dip angle of 42°, which is almost pure reverse fault (slip angle 87°) with a dislocation of 1 meter. The numerical simulation shows that the shallow sea in the source region caused a comparatively long recurring tsunami (the periods are 12–18 minutes) in spite of its small size. The model fault is corresponding to an aftershock area of this earthquake. 相似文献
9.
海平面的海啸波会产生大气重力波进而引发电离层扰动.本文利用日本GPS总电子含量数据来探测2011年3月11日Tohoku海啸引发的电离层扰动.观测结果表明,在日本上空的电离层中存在两种重力波信号,分别由海平面的海啸波以及地震破裂过程产生.地震产生的电离层重力波分布在震中周围（包括海洋上空以及远离海洋的区域）,而海啸引发的电离层重力波主要分布在海洋上空.地震产生的电离层重力波具有不同的水平速度,包括约210 m·s-1以及170 m·s-1,其频率为1.5 mHz;而海啸引发的电离层重力波水平速度快于前者,约为280 m·s-1,其频率为1.0 mHz.此外,海啸引发电离层重力波与海平面上的海啸波有相似的水平速度、方向、运行时间、波形以及频率等传播特征.本文的研究将电离层中的海啸信号与地震信号区分开来,进一步确认电离层对海啸波的敏感性. 相似文献
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Dates of tsunami deposits have been used to estimate paleotsunami recurrence intervals in areas affected by these natural events. The depositional age of tsunami deposits is commonly constrained by the radiocarbon (14C) dating of sediments above and below the geological event. However, because of calibration curve fluctuations, the depositional age sometimes has a wide error range. In this study, we conducted millimeter-scale high-resolution radiocarbon measurements of tsunami deposits at Urahoro in southern Hokkaido, Japan. The site faces the Pacific Ocean along the Kuril Trench. Eight event deposits were identified within peat at this site. We took sequential measurements for 14C dating using bulk peat samples. The results were validated based on comparison with the absolute and radiometric ages of tephra layers. Dating results were further constrained by stratigraphic order using statistical methods. We constrained the depositional age of the paleotsunami deposits better using this method than we did when using conventional methods. We proposed an efficient measurement strategy with respect to the radiocarbon calibration curve. This method is also applicable for other deposits formed by any natural hazard if bulk peat is obtainable so it can contribute to better hazard assessment worldwide. 相似文献
13.
Abstract Quaternary volcanism of the Japanese Islands is examined from the perspective of experimental petrology, geographic distribution of volcanoes and spatial geochemical variations. The dehydration of amphibole and chlorite at a 110 km depth and of phlogopite at ∼180 km in the downdragged hydrous mantle layer would result in the occurrence of two volcanic chains parallel to the trench axis. Long-term subduction of the old Pacific plate and recent subduction of the young Philippine Sea plate beneath East Japan and West Japan volcanic belts respectively, would be critical for the significant difference in intensity, style and geochemistry of Quaternary volcanism between the two volcanic belts. The geochemistry of volcanic rocks in Northeast Japan and those in the Ryukyu arc is typical of 'island-arcs' having low LIL/HFS element ratios, while alkalic basalts along the Japan Sea coast side in Southwest Japan have high LIL/HFS ratios similar to intra-continental or oceanic island basalts. Across-arc variations in eruptive volume and distributional density of volcanoes and in geochemistry are documented in Northeast Japan and are well explained by the decreasing degrees of partial melting toward back-arc side, and the difference in geochemistry of fluids supplied by the downdragged hydrous layer. 相似文献
14.
Hitoshi Tanaka Kosuke Kayane Mohammad Bagus Adityawan Min Roh Mohammad Farid 《Ocean Dynamics》2014,64(9):1319-1332
The relations of river morphology and tsunami propagation in rivers were studied at several rivers in the Tohoku region during The Great Chilean Tsunami of 2010 and The Great East Japan Tsunami of 2011. It was found that river mouth morphological features play an important role in the intrusion of low magnitude tsunamis in which the geological and geographical conditions are an important factor. Nevertheless, the effects of these features were not found in the case of an extreme tsunami wave. As the wave enters the river, the propagation depends on other factors. It was found that the intrusion distance correlates well to the riverbed slope. The measurements of water level and riverbed slope were analyzed to propose an empirical method for estimating the damping coefficient for the tsunami propagation in rivers based on the tsunami of 2011. The proposed empirical method was used to approximate the length of the tsunami intrusion into a river by assuming that the furthest distance is given for the ratio of local tsunami wave height to the tsunami wave height at the river entrance of 0.05 (5 %). The estimated intrusion length from the proposed method in this study shows a good comparison with measurement data. 相似文献
15.
This study conducts coupled simulation of strong motion and tsunami using stochastically generated earthquake source models. It is focused upon the 2011 Tohoku, Japan earthquake. The ground motion time-histories are simulated using the multiple-event stochastic finite-fault method, which takes into account multiple local rupture processes in strong motion generation areas. For tsunami simulation, multiple realizations of wave profiles are generated by evaluating nonlinear shallow water equations with run-up. Key objectives of this research are: (i) to investigate the sensitivity of strong motion and tsunami hazard parameters to asperities and strong motion generation areas, and (ii) to quantify the spatial variability and dependency of strong motion and tsunami predictions due to common earthquake sources. The investigations provide valuable insights in understanding the temporal and spatial impact of cascading earthquake hazards. Importantly, the study also develops an integrated strong motion and tsunami simulator, which is capable of capturing earthquake source uncertainty. Such an advanced numerical tool is necessary for assessing the performance of buildings and infrastructure that are subjected to cascading earthquake–tsunami hazards. 相似文献
16.
A global ocean circulation model is coupled to a particle-tracking model to simulate the transport of floating debris washed into the North Pacific Ocean by the Tohoku tsunami. A release scenario for the tsunami debris is based on coastal population and measured tsunami runup. Archived 2011/2012 hindcast current data is used to model the transport of debris since the tsunami, while data from 2008 to 2012 is used to investigate the distribution of debris on timescales up to 4 years. The vast amount of debris pushed into ocean likely represents thousands of years worth of ‘normal’ litter flux from Japan’s urbanized coastline. This is important since a significant fraction of the debris will be comprised of plastics, some of which will degrade into tiny particles and be consumed by marine organisms, thereby allowing adsorbed organic pollutants to enter our food supply in quantities much higher than present. 相似文献
17.
Tsunami damage to coastal defences and buildings in the March 11th 2011 M
w
9.0 Great East Japan earthquake and tsunami 总被引：2，自引：0，他引：2
Stuart Fraser Alison Raby Antonios Pomonis Katsuichiro Goda Siau Chen Chian Joshua Macabuag Mark Offord Keiko Saito Peter Sammonds 《Bulletin of Earthquake Engineering》2013,11(1):205-239
On March 11th 2011 a M w 9.0 mega-thrust interface subduction earthquake, the Great East Japan Earthquake, occurred 130 km off the northeast coast of Japan in the Pacific Ocean at the Japan Trench, triggering tsunami which caused damage along 600 km of coastline. Observations of damage to buildings (including vertical evacuation facilities) and coastal defences in Tōhoku are presented following investigation by the Earthquake Engineering Field Investigation Team (EEFIT) at 10 locations in Iwate and Miyagi Prefectures. Observations are presented in the context of the coastal setting and tsunami characteristics experienced at each location. Damage surveys were carried out in Kamaishi City and Kesennuma City using a damage scale for reinforced concrete (RC), timber and steel frame buildings adapted from an earlier EEFIT tsunami damage scale. Observations show that many sea walls and breakwaters were overtopped, overturned, or broken up, but provided some degree of protection. We show the extreme variability of damage in a local area due to inundation depth, flow direction, velocity variations and sheltering. Survival of many RC shear wall structures shows their high potential to withstand local earthquake and significant tsunami inundation but further research is required into mitigation of scour, liquefaction, debris impact, and the prevention of overturning failure. Damage to steel and timber buildings are also discussed. These observations are intended to contribute to mitigation of future earthquake and tsunami damage by highlighting the key features which influence damage level and local variability of damage sustained by urban coastal infrastructure when subjected to extreme tsunami inundation depths. 相似文献
18.
Hisashi Kuno 《Bulletin of Volcanology》1959,20(1):37-76
Three petrographic provinces can be recognized in the Cenozoic volcanic fields of Japan and surrounding areas. A province of a tholeiite series lies on the Pacific side of the Japanese Islands and includes the Izu Islands, whereas that of an alkali rock series occupies the Japan Sea side of the Islands with a narrow offshoot extending across central Honsyū (Honshū) and a continuation westward to Korea and Manchuria. A province of a calc-alkali rock series is superposed on the two provinces and occupies the greater part of the Japanese Islands exclusive of the Izu Islands and the islands in the Japan Sea southwest of Honsyū and north of Kyūsyū (Kyūshū). The boundary lines between the tholeiite and alkali provinces are located very closely to those between the areas where earthquakes occur at depths shallower than about 200 km and those for deeper ones. It is suggested that the parental tholeiite magma is produced by partial melting of the periodotite layer at depths shallower than 200 km. In the Izu Islands, except Nii-zima(Nii-jima) and Kōzu-sima(Kōzu-shima) close to Honsyū, the magma erupts to the surface without assimilating granitic material because the granitic layer is absent, resulting in volcanoes made up exclusively of the tholeiite series. The parental alkali olivine basalt magma is produced by partial melting of the peridotite layer at depths greater than 200 km. In the Japan Sea region, Korea, and Manchuria, it erupts to the surface without assimilating the granitic material, although it passes through a thick granitic layer, resulting in volcanoes made up exclusively of the alkali series. However, in the Cenozoic orogenic belt of the Japanese Islands, both types of parental magma assimilate granitic material during passage to the surface and erupt to form volcanoes of the calc-alkali series. 相似文献
19.
Katsuyuki Abe 《Pure and Applied Geophysics》1995,144(3-4):735-745
The Hokkaido-Nansei-Oki earthquake (M
w
7.7) of July 12, 1993, is one of the largest tsunamigenic events in the Sea of Japan. The tsunami magnitudeM
t
is determined to be 8.1 from the maximum amplitudes of the tsunami recorded on tide gauges. This value is larger thanM
w
by 0.4 units. It is suggested that the tsunami potential of the Nansei-Oki earthquake is large forM
w
. A number of tsunami runup data are accumulated for a total range of about 1000 km along the coast, and the data are averaged to obtain the local mean heightsH
n
for 23 segments in intervals of about 40 km each. The geographic variation ofH
n
is approximately explained in terms of the empirical relationship proposed byAbe (1989, 1993). The height prediction from the available earthquake magnitudes ranges from 5.0–8.4 m, which brackets the observed maximum ofH
n
, 7.7 m, at Okushiri Island. 相似文献
20.
The 2011 Tohoku-oki tsunami caused large-scale topographic changes along the Pacific coast of northeastern Japan. More than 10 years have passed since the tsunami waves struck the area. Today, because of reconstruction work, very few places exist where natural post-tsunami topographic changes can be monitored continuously. For this study, the authors investigated topographic changes caused not only by the 2011 tsunami but also by natural and artificial activities during the 50 years before and after the tsunami based on aerial photographs, excavations and subsurface explorations using ground-penetrating radar at the Osuka coast in Aomori prefecture, Japan. The site is rare because it is a protected area with few and superficial engineering activities, making it suitable for continuous observation of pre-tsunami, syn-tsunami and post-tsunami topographic changes. The findings indicate that the 2011 tsunami waves generated large topographic changes: depositional and erosional features produced by the tsunami can be recognized, respectively, as tsunami deposits and erosional channels across the sand dunes. During the post-tsunami phase, the sand volume at the coast quickly recovered naturally. Tsunami deposits and the erosional channels were well preserved underground even at 10 years after the event. However, dynamic movement of the dunes started after the tsunami. The shifting was attributable to the artificial clearing of coastal forests rather than the tsunami effects on the coast. Our results first indicate not only that the sedimentary features of paleo-tsunamis but also the erosional features have some probability of being preserved in the subsurface of the beach and sand dunes at tsunami-affected areas. Also, artificial activities such as deforestation are much more crucially undermining of the stability of the coastal geomorphology than the tsunami effects: the coast is now reaching a different status from its pre-tsunami situation. 相似文献