Use of tsunami waveforms for earthquake source study   总被引：1，自引：0，他引：1  

Kenji Satake  Hiroo Kanamori 《Natural Hazards》1991,4(2-3):193-208

Tsunami waveforms recorded on tide gauges, like seismic waves recorded on seismograms, can be used to study earthquake source processes. The tsunami propagation can be accurately evaluated, since bathymetry is much better known than seismic velocity structure in the Earth. Using waveform inversion techniques, we can estimate the spatial distribution of coseismic slip on the fault plane from tsunami waveforms. This method has been applied to several earthquakes around Japan. Two recent earthquakes, the 1968 Tokachi-oki and 1983 Japan Sea earthquakes, are examined for calibration purposes. Both events show nonuniform slip distributions very similar to those obtained from seismic wave analyses. The use of tsunami waveforms is more useful for the study of unusual or old earthquakes. The 1984 Torishima earthquake caused unusually large tsunamis for its earthquake size. Waveform modeling of this event shows that part of the abnormal size of this tsunami is due to the propagation effect along the shallow ridge system. For old earthquakes, many tide gauge records exist with quality comparable to modern records, while there are only a few good quality seismic records. The 1944 Tonankai and 1946 Nankaido earthquakes are examined as examples of old events, and slip distributions are obtained. Such estimates are possible only using tsunami records. Since tide-gauge records are available as far back as the 1850s, use of them will provide unique and important information on long-term global seismicity.  相似文献   

Analysis and automatic processing in near-field of eight 1992–1994 tsunamigenic earthquakes: Improvements towards real-time tsunami warning     

F. Schindelé  D. Reymond  E. Gaucher  E. A. Okal 《Pure and Applied Geophysics》1995,144(3-4):381-408

We study eight tsunamigenic earthquakes of 1992–1994 with data from single near-field 3-component long-period stations. The analysis is made from the standpoint of tsunami warning by an automatic process which estimates the epicentral location and the seismic moment through the variable-period mantle magnitudeM _m . Simulations of early warning based on the real-time computation of the seismic moment are also tested with this system, which would give a justified warning in each region of tsunami potentiality. By exploiting the dependence of moment rate release with frequency, the system has the capability of recognizing both tsunami earthquakes such as the 1992 Nicaragua and 1994 Java events, as well as instances of the opposite case of low-frequency deficiency, interpreted as indicating a deeper than normal source (1993 Guam event). We report both the results of delayed-time processing of the near-field stations, and the actual real-time warnings at PPT, which confirm the former.  相似文献   

Manila’s metropolitan landscape of gentrification: Global urban development,accumulation by dispossession & neoliberal warfare against informality     

《Geoforum》2016

A new regime of gentrification is dramatically restructuring Manila’s metropolitan landscape. Grounded upon an on-going neoliberal warfare of accumulation by dispossession, this gentrification serves as the fulfillment of postcolonial visions of a world class and modern metropolis through public–private arrangements and market-oriented developments but necessitates the systematic demolition of informal settlements, the home of the Manila’s urban poor and working class population. Through a mixed-methods approach, this paper examines gentrification’s spatial forms and trajectories and exposes context specific dynamics facilitating accumulation by dispossession. Using barangay (village)-level data on changes in population of informal households and median zonal values, I calculate for local measures of spatial autocorrelation and locate significant clusters of spatial shifts. Using the quantitative results plus field narratives and community histories, I triangulate local dynamics of accumulation by dispossession. What emerges is a sprawling gentrification process that, in producing a market-oriented metropolis, displaces and asphyxiates informal spaces. These accounts illustrate the contingencies of violence, neoliberal urbanism, colonial legacies of land regimes, and elite power in the production of a globally-competitive Manila. With other Global South megacities similarly competing in the global market, gentrification in Manila, with its expanding landscape of property accumulation and ’legitimized’ dispossession, is instructive of the emerging form of gentrification in the 21st century.  相似文献   

海啸波作用下泥沙运动——Ⅴ.红树林影响下的岸滩变化          下载免费PDF全文

陈杰  管喆  蒋昌波 《水科学进展》2016,27(2):206-213

近年来频发的海啸灾害造成巨大损失,而红树林具有很好的减小海啸灾害的作用。实验采用PVC圆管来概化模拟红树林,以无黏性沙堆砌而成1/10~1/20组合坡概化岸滩,选取孤立波模拟海啸波。实验结果表明,红树林的存在对岸滩剖面变化产生了较大影响,适当增加植物分布密度,并优化植物的分布方式,可有效减小海啸波对岸滩的冲刷危害。在本次实验条件下,得到了岸滩冲刷坑尺度、淤积沙坝尺度、最大冲刷深度、最大淤积高度与红树林的分布方式和密度、海啸波波高、泥沙比重和岸滩坡度之间的关系式,揭示了沙质岸滩剖面变化与红树林、海啸波水动力特性、泥沙颗粒、岸滩坡度之间的内在联系,为减小海啸灾害提供科学依据。  相似文献   

Identification of Perkinsus-like parasite in Manila clam, Ruditapes philippinarum using DNA molecular marker at ITS region   总被引：1，自引：0，他引：1  

ZHANG Xichang  LIANG Yubo  FAN Jingfeng  ZHANG Wei  PU Hongyu  LIANG Bin  CHEN Hongxing  SONG Lichao 《海洋学报(英文版)》2005,24(5):139-144

Genomic DNA was extracted from hypnospores of Perkinsus-like parasite of Manila clam Ruditapes philippinarum collected at the fishing grounds in Huanghai Sea coast Shicheng Island and East China Sea coast Ningbo, China. The internal transcribed spacer（ITS） in rDNA was PCR-amplified, cloned, sequenced, and compared with that of five Perkinsus species in GenBank. The fragment amplified from DNA of parasite of either Shicheng Island or Ningbo contained 649 bp, including partial ssrRNA（51 bp） and ITS（＋5.8 S） （598 bp） regions. The ITS（＋5.SS） sequences of Perkinsus-like parasite of both Shicheng Island and Ningbo were all 99% identical to those ofPerkinsis atlanticus, and were not more than 95% identical to those of other four Perkinsus species including P. marinus, P. andrewsi, P. qugwadi and P. medierraneus.The ITS （＋5.8S） sequence of Perkinsus-like parasite of Shicheng Island was 99% identical to that of Ningbo. These facts about nucleotide sequences suggested that the Perkinsus-like parasite in Manila clam, Ruditapes philippinarum collected from either the Huanghai Sea coast or the East China Sea coast was P. atlanticus, and might reflect P. atlanticus strains of distinct geographic distribution.  相似文献   

The effects of variable speeds of a submarine block slide on near-field tsunami amplitudes   总被引：2，自引：0，他引：2  

Abdul Hayir   《Ocean Engineering》2003,30(18):2329-2342

In this study, the motion of a submarine block slide, with variable velocities, and its effects on the near-field tsunami amplitudes are investigated. The numerical results show that the amplitudes generated by the slide are almost the same as those created by its average velocity when , where is average velocity of the slide and is the long period tsunami velocity in ocean of constant depth h. In contrast, the kinematic model of the slide must take into account time variations in the moving velocity, if , especially when .  相似文献   

Energetics of the Tsunami of 26 December 2004 in the Indian Ocean: A Brief Review     

N. Nirupama  T. S. Murty  I. Nistor  A. D. Rao 《Marine Geodesy》2006,29(1):39-47

The energetics of the most destructive tsunami in historical time, and that of the under ocean earthquake that triggered this tsunami of 26 December 2004 in the Indian Ocean have been briefly reviewed. This latest tsunami has several other unique characteristics besides being one of the worst natural disasters in human history. It is the first truly global tsunami after modern seismographic and sea level monitoring networks have been put in place. It was the first tsunami on record detected by a satellite, even though at present, global satellite coverage of the oceans for real time tsunami detection is not adequate. Finally, the energy associated with the tsunami and the earthquake that triggered it is so large that speculation has been made about the normal modes of oscillation of the earth, that were triggered by the earthquake as well as some suggestions, that some of the earth's rotational characteristics may have temporarily changed to a discernible degree. Here, we briefly review the energetics of the tsunami and the earthquake that triggered it.  相似文献   

Propagation and run-up of nearshore tsunamis with HLLC approximate Riemann solver     

Dae-Hong Kim  Yong-Sik Cho  Yong-Kon Yi   《Ocean Engineering》2007,34(8-9):1164-1173

A numerical model describing the propagation and run-up process of nearshore tsunamis in the vicinity of shorelines is developed based on an approximate Riemann solver. The governing equations of the model are the nonlinear shallow-water equations. The governing equations are discretized explicitly by using a finite volume method. The nonlinear terms in the momentum equations are solved with the Harten-Lax-van Leer-Contact (HLLC) approximate Riemann solver. The developed model is first applied to prediction of water motions in a parabolic basin, and propagation and subsequent run-up process of nearshore tsunamis around a circular island. Computed results are then compared with available analytical solutions and laboratory measurements. Very reasonable agreements are observed.  相似文献   

浙江沿海潜在区域地震海啸风险分析   总被引：3，自引：2，他引：1  

毛献忠  祝倩  Wei Yong 《海洋学报》2015,37(3):37-45

采用COMCOT海啸模型建立三重网格模型模拟了2011年3月11日日本东北部9.0级地震引发的海啸发生、发展以及在我国东南沿海传播过程。震源附近浮标站以及浙江沿海的潮位站实测资料验证结果显示,大部分监测站首波到达时间和海啸波的计算值相差在15%以内,表明模型可较好的模拟海啸在计算域内的传播过程。研究表明日本南海海槽、冲绳海槽以及琉球海沟南部是影响浙江沿海主要的区域潜在震源,通过情景计算分别模拟3个潜在震源9.1级、8.0级和8.7级地震引发的海啸对浙江沿海的海啸风险,计算结果表明,海啸波产生后可在3~8h内传至浙江省沿岸,海啸波达1~3m,最大可达4m,此时浙江沿岸面临Ⅲ~Ⅳ级海啸风险,达到淹没至严重淹没等级。  相似文献   

东海海啸反问题预报模式研究——以日本“3·11”海啸为例     

应超  于普兵  穆锦斌  周华民 《海洋预报》2015,32(3):36-42

采用COMCOT数值模式,将日本东海岸划分为18个单位震源,建立了日本东海岸海啸数据库并用非负约束的最小二乘法建立反问题预报模式。将本模式应用于日本"3·11"海啸,计算所得的海啸初始水位有10 m的抬高与3 m的降低,与前人研究结果基本一致,预报的浮标水位与实测资料符合良好。对比浙江省近岸潮位站实测海啸波高,预报值与实测值偏差较大。若采用反问题反演的震源,通过COMCOT非线性模式求解近岸水位,可以大幅提高预报精度。  相似文献