Tsunami Inundation Modelling for the Coast of Kerala,India

The disastrous tsunami of December 26, 2004, exposed the urgent need for implementing a tsunami warning system. One of the essential requirements of a tsunami warning system is the set up of tsunami inundation models which can predict inundation and run-up along a coastline for a given set of seismic parameters. The Tsunami Warning Centre and the State/District level Disaster Management Centres should have tsunami inundations maps for different scenarios of tsunami generation. In the event of a tsunamigenic earthquake, appropriate decisions on issue of warnings and/or evacuation of coastal population are made by referring to such maps. The nature of tsunami inundation and run-up along the Kerala coast for the 2004 Sumatra and 1945 Makran, and a hypothetical worst-case scenario are simulated using the TUNAMI N2 model and the results are presented in this paper. Further, scenarios of tsunami inundation arising out of possible rise in sea level as projected by the Intergovernmental Panel on Climate Change (IPCC 2001) are also simulated and analysed in the paper. For the study, three representative sectors of the Kerala coast including the Neendakara-Kayamkulam coast, which was the worst hit by the 2004 tsunami, are chosen. The results show that the southern locations and certain locations of central Kerala coast are more vulnerable for Sumatra when compared to Makran 1945 tsunami. From the results of numerical modelling for future scenarios it can be concluded that sea level rise can definitely make pronounced increase in inundation in some of the stretches where the backshore elevation is comparatively low.     

Relevance of Bathymetry for Tsunami Run‐up Modeling

Abstract

Marine positioning is relevant for several aspects of tsunami research, observation, and prediction. These include accurate positioning of instruments on the ocean bottom for determining the deep‐water signature of the tsunami, seismic observational setups to measure the earthquake parameters, equipment to determine the tsunami characteristics during the propagation phase, and instruments to map the vertical uplift and subsidence that occurs during a dip‐slip earthquake.

In the accurate calculation of coastal tsunami run‐up through numerical models, accurate bathymetry is needed, not only near the coast (for tsunami run‐up) but also in the deep ocean (for tsunami generation and propagation). If the bathymetry is wrong in the source region, errors will accumulate and will render the numerical calculations inaccurate. Without correct and detailed run‐up values on the various coastlines, tsunami prediction for actual events will lead to false alarms and loss of public confidence.     

一个基于GPU并行加速的海啸数值模型

地震海啸通常发生在大洋板块向陆地板块俯冲的区域,距离震源最近的国家和地区往往在震后5～20 min之内就会遭受到海啸袭击。因此,及时的海啸预警和准确的海啸预报结果对于民众和决策者都至关重要。为了提升海啸预警效率,缩短海啸预报时间,本研究对COMCOT海啸数值模型进行了基于图形计算单元GPU的二次并行开发。将原模型中海啸传播计算模块通过CUDA＿C语言编写内核函数整体移植到GPU上并行加速,CPU负责模型其他代码的执行。为了减少CPU和GPU之间的数据通信,将吸收边界和变量更新函数一并改写。仅在需要输出的时间节点,GPU向CPU传递结果,其他时间步长,CPU和GPU之间只有指令和少量参数传输,基本可视为零耗时。基于GPU并行加速的COMCOT较串行版本效率提升超过67倍,加速性能显著优于基于CPU共享内存的OpenMP并行版本。交叉使用常水深和真实地形,采用均匀滑移海啸源和有限元海啸源对模型的计算结果进行了较为全面的分析检验,相对误差最大不超过1%,为大范围的越洋海啸实时计算提供了有力工具。     

Regional long-period magnitude scales and their capabilities for tsunami warning

The tsunami warning system in the Russian Far East employs the medium-period magnitude MS (BB) by Vaniek–Soloviev. However, its use may lead to inadequacies and underestimates for the tsunamigenic potential of an earthquake. Specifically, this can happen in the case of a so-called tsunami–earthquake. This kind of earthquakes with a nonstandard spectrum was revealed by H. Kanamori in 1972. This problem can be overcome by using a magnitude scale that deals with longer period seismic waves. This study develops a technique for determining the magnitudes at regional distances (from 70 to 4500 km) using the amplitudes of surface seismic waves of periods of 40 and 80 s. At distances of 70–250 km, the amplitude of the joint group of shear and surface waves is used. For the new magnitudes designated M _S(40) and M _S(80), experimental calibration curves are constructed using more than 1250 three-component records at 12 stations of the region. The magnitudes are calibrated so as to produce an unbiased estimate of the moment magnitude M _w in the critical range 7.5–8.8. The rms error of the single-station estimate M _w is around 0.27. At distances below 250 km and M _w ≥ 8.3, the estimate of M _w obtained by the proposed technique becomes saturated at the level of M _w ~ 8.3, which is acceptable for operative analysis because no missed alarms arise. The technique can be used in operational tsunami warning based on seismological data. This can markedly decrease the number of false alarms.     

精细化地震海啸波流实时预警系统研究与应用

基于Okada模型和非线性浅水波模型,结合高精度多层嵌套网格针对我国浙江沿海的温州和台州地区建立了越洋–近海–局部的精细化地震海啸波流实时预警系统,近岸的分辨率为900 m。该预警系统包括了并行化的数值计算模块,基于Python 2D绘图库的计算结果可视化处理模块,以及通过Python语言将所有经过数值计算的图形与动画产品集成在一个网页上的产品集成模块。一旦地震发生,该系统可根据地震的震源参数信息在10 min内完成数值计算、可视化处理,以及产品集成。选取2011年日本东北9.0级地震海啸结合实测数值对该系统进行模拟验证,进一步应用该系统模拟计算了日本南海海槽和琉球海沟潜在极端海啸的影响规律。结果表明,该预警系统可有效地提高地震海啸实时预警的时效性和准确度,为海啸的预警、减灾,以及辅助决策提供科学依据。     

Managing tsunamis through early warning systems: A multidisciplinary approach

This study attempts to identify the key factors that will make a tsunami warning system most effective, to develop a framework in which results of natural science and engineering research can be effectively integrated into coastal natural hazard planning, and to develop a numerical example that illustrates how benefit-cost analysis may be used to assess early warning systems. Results of the study suggest that while the science of tsunami wave propagation and inundation is relatively advanced, our knowledge on the relationships between tsunami generation and undersea earthquakes, volcanic eruptions, and landslides remains poor, resulting in significant uncertainties in tsunami forecasting. Probabilities of damaging tsunamis for many coastal regions are still unknown, making tsunami risk assessment and management difficult. Thus it is essential to develop new techniques to identify paleo-tsunami events and to compile and develop size and frequency information on historical tsunamis for different locations. An effective tsunami early warning system must include not only the ocean technologies for accurately detecting an emerging tsunami, but also a civil communication system through which the population can be timely warned by the local government and other sources. Since minimizing the evacuation time is a key factor to make a warning system effective, adequate pre-event education and preparation of the population must be a critical component of the system. Results of a numerical example of the South Pacific region suggest that investments in a tsunami warning system in the region may lead to significant economic benefits.     

Retrospective short-term forecast of the 1996 Andreanov (Aleutian Islands) tsunami

A brief review of the problem of short-term (operative) tsunami forecasting is presented. A method of short-term tsunami forecasting based on the sea level data at remote points is described. The forecast is based only on the seismological information about the coordinates of the earthquake’s epicenter. The application of this method for a retrospective forecast of the 1996 Andreanov tsunami demonstrates a satisfactory coincidence with the predicted and observed tsunami waveforms. The results are compared with the modeling prediction of the same event by other authors. The suggested method of the operative tsunami forecast can serve a basis for the development of a unique programming complex for operative forecasting and can be realized within regional and local tsunami warning services. The method can be used in tsunami warning systems at the stage of their development.     

我国海啸灾害及预警现状与建议

本文给出了海啸定义及其它有关概念与术语,简要给出了我国及全球的海啸灾害.全面介绍了我国海啸监测能力、预警现状、研究成果以及有关国际合作的情况,重点介绍了我国自主研制的海啸数值模式,利用该模式我们模拟了2004年12月26日发生在印度洋大海啸以及假想的发生在我国南海的海啸对周边国家的影响.对海啸预警中存在的问题及未来急需开展的工作,作者也将一一给予阐述.     

Tsunami detectability using open-ocean bottom pressure fluctuations

Rationale for the measurement of open-ocean tsunami signatures are presented, and available pertinent data are reviewed. Models for tsunami signature and background noise are proposed in order to synthesize an optimum tsunami receiver. Using these models, the minimum tsunami amplitude (in cm) to yield the probability of correct tsunami detectionP_{D} = 0.999and probability of false alarmP_{F} = 10^{-3}is found to be0.718/sqrt{f_{0}}, wheref_{0}is the tsunami dominant frequency (in cycles/h). A realizable receiver is proposed and its performance is evaluated using actual tsunami signatures. It is demonstrated that the detection of a tsunami with an average amplitude as small as 0.7 cm is possible for theP_{D}andP_{F}as above. Simulation results using synthesized background noise are shown. Tidal effects on the receiver performance also are considered and are found negligible for a certain range of the receiver parameters, resulting in a considerable reduction of the signal processing required.     

Short-Term Morphological and Shoreline Changes at Trinkat Island,Andaman and Nicobar,India, After the 2004 Tsunami

The tsunami waves generated during the Sumatra-Andaman earthquake of 26 December 2004 devastated the coastal area along Trinkat Island, causing sudden changes to the morphology of the landforms. This study uses a series of satellite images to record the short-term morphological response and shoreline changes as well as the recovery of coastal land after its destruction. Results indicate that the island experienced substantial erosion and a significant reduction in land area. Shoreline erosion is more prevalent than accretion at an average linear regression rate of ～?9 m per year between 2004 and 2013. The major morphological changes at Trinkat Island were observed in coastal inlets, beaches, and bay head-lands. Straight beaches had almost recovered eight years after the tsunami; however, erosion is continually observed in other areas. Our study will help understanding the response and recovery of shorelines in Indian Ocean regions after the 2004 tsunami.     

Marine reserve establishment and on-going management costs: A case study from New Zealand

While there is considerable international research focused on the conservation outcomes of marine protected areas (MPAs) and marine reserves (MRs) there is little information on the economic cost to establish and manage these protected areas. This study estimated the MR pre-establishment and establishment costs for the Taputeranga Marine Reserve (TMR) in New Zealand (NZ) and determined the annual management costs for this reserve and four further NZ MRs. Finally, the cost to local rock lobster fishers resulting from the displaced fishing effort once the TMR had been established was estimated. This research found that the TMR pre-establishment cost was approximately NZ$508,000, and the establishment process cost was approximately NZ$353,000. The annual management costs across the five reserves ranged between NZ$43,200 and NZ$112,500 between 2008/09 and 2010/11. The annual fishers displacement cost at TMR was approximately NZ$22,000 per annum. This research showed that on a unit area basis, small MRs in NZ are just as expensive to maintain as large MRs. This study also highlighted how volunteer effort helped to considerably reduce the monetary cost of the MR pre-establishment process. This research increases our understanding of establishment and management costs, and supports future planning of MRs both within NZ and internationally.     

Global catches,exploitation rates,and rebuilding options for sharks

Adequate conservation and management of shark populations is becoming increasingly important on a global scale, especially because many species are exceptionally vulnerable to overfishing. Yet, reported catch statistics for sharks are incomplete, and mortality estimates have not been available for sharks as a group. Here, the global catch and mortality of sharks from reported and unreported landings, discards, and shark finning are being estimated at 1.44 million metric tons for the year 2000, and at only slightly less in 2010 (1.41 million tons). Based on an analysis of average shark weights, this translates into a total annual mortality estimate of about 100 million sharks in 2000, and about 97 million sharks in 2010, with a total range of possible values between 63 and 273 million sharks per year. Further, the exploitation rate for sharks as a group was calculated by dividing two independent mortality estimates by an estimate of total global biomass. As an alternative approach, exploitation rates for individual shark populations were compiled and averaged from stock assessments and other published sources. The resulting three independent estimates of the average exploitation rate ranged between 6.4% and 7.9% of sharks killed per year. This exceeds the average rebound rate for many shark populations, estimated from the life history information on 62 shark species (rebound rates averaged 4.9% per year), and explains the ongoing declines in most populations for which data exist. The consequences of these unsustainable catch and mortality rates for marine ecosystems could be substantial. Global total shark mortality, therefore, needs to be reduced drastically in order to rebuild depleted populations and restore marine ecosystems with functional top predators.     

What is an endangered species worth? Threshold costs for protecting imperilled fishes in Canada

The protection of imperilled fish species is increasingly urgent given ongoing fisheries declines and the degradation of aquatic habitats. In Canada, threatened aquatic species were less likely than terrestrial species to be listed under the Species at Risk Act (SARA), the main legal instrument for bestowing protection, in the early years of the Act's implementation. In this paper, the existence of economic thresholds that might have hampered the protection of Canadian marine and freshwater fishes is examined. The analysis of the socio-economic data used to inform listing decisions about threatened fish taxa over the past decade reveals that the likelihood of being listed declines non-linearly with increasing estimated costs of protection but does not vary with proposed threat status. The estimated threshold cost (i.e., the point at which the likelihood of not being listed=0.5) was ∼$5,000,000 (∼$1,400,000 to ∼$31,400,000, 95% CI) per decade for freshwater species but only ∼$90,000 ($∼50,000 to ∼$140,000, 95% CI) per decade for marine fish taxa. In fact, no marine fish species with an anticipated cost of listing greater than zero was listed for protection. The presence of existing management legislation and qualitative statements about negative impacts of listing on exploitation generally led to denying protection to marine but not to freshwater species. These findings highlight both a large and inconsistent emphasis on costs of protection in SARA listing decisions, to the detriment of marine fish species.     

一个覆盖太平洋区域的地震海啸波幅预报系统及检验

基于线性长波方程和缓变地形近岸波幅格林公式建立了覆盖整个太平洋区域的准实时地震海啸波幅预报系统。系统利用了GPU并行加速技术,可在90 s之内完成太平洋区域32 h的海啸传播计算和中国沿海城市岸段的波幅特征值预报。筛选了自2006年以来的9次发生在太平洋区域,矩震级（Mw）超过8.0且资料丰富的历史地震海啸事件,对预报系统进行了后报检验。结果表明,线性长波模型能够很好的模拟海啸在大洋中的传播过程;格林公式能够较为准确的估算缓变水深和开阔地形条件下的近岸海啸最大波幅,波幅预警准确率可达80%,基本满足海啸预警需求。以2011年日本Mw9.0地震海啸为例,评估了该系统对中国城市岸段的波幅预警能力,结论基本合理。需要注意的是,利用该系统计算对海啸源特别敏感的近场海啸波幅可能产生较大偏差。提出了若要进一步提高定量海啸波幅预警的准确率,可从以下两个方面加强研究和业务实践:一是采用多数据联合反演方法提升海啸源的精度;二是提高格林公式的适用性,或者构建高效的近岸精细化海啸数值预报系统。     

The migrant anchovy fishery in Kabui Bay,Raja Ampat,Indonesia: Catch,profitability, and income distribution

We estimate the unregulated catch and fisher income of the Kabui Bay migrant anchovy fishery operating in the Raja Ampat regency, Papua, Indonesia. Interviews with migrant fishers were conducted in April and November 2006, and estimates were generated through Monte Carlo simulations. Anchovy fisher income averaged US $1835 per year, about twice the average fisher income in the area. The income levels estimated by this study suggests that there is potential for the Raja Ampat Fisheries Bureau to capture some economic rent from the fishery to help fund a fisheries management program, from which Raja Ampat could benefit.     

有限断层模型在2015年9月16日智利Mw8.3级地震海啸数值模拟中的应用与评估

2015年9月16日22时54分（当地时间）智利中部近岸发生M_w8.3级地震,震源深度25 km。同时,强震的破裂区长200 km,宽100 km,随之产生了中等强度的越洋海啸。海啸影响了智利沿岸近700 km的区域,局部地区监测到近5 m的海啸波幅和超过13 m的海啸爬坡高度。太平洋区域的40多个海啸浮标及200多个近岸潮位观测站详细记录了此次海啸的越洋传播过程,为详细研究此次海啸近场及远场传播及演化规律提供了珍贵的数据。本文选择有限断层模型和自适应网格海啸数值模型建立了既可以兼顾越洋海啸的计算效率又可以实现近场海啸精细化模拟的高分辨率海啸模型。模拟对比分析了海啸的越洋传播特征,结果表明采用所建立的模型可以较好地再现远场及近场海啸特征,特别是对近场海啸的模拟结果非常理想。表明有限断层可以较好地约束近场、特别是局部区域的破裂特征,可为海啸预警提供更加精确的震源信息,结合高分辨率的海啸数值预报模式实现海啸传播特征的精细化预报。本文结合观测数据与数值模拟结果初步分析了海啸波的频散特征及其对模型结果的影响。同时对观测中典型的海啸波特征进行的简要的总结。谱分析结果表明海啸波的能量主要分布在10~50 min周期域内。这些波特征提取是现行海啸预警信息中未涉及,但又十分重要的预警参数。进一步对这些波动特征的详细研究将为海啸预警信息及预警产品的完善提供技术支撑。     

Tsunami observations in the open ocean

Deep-sea tsunami measurements play a major role in understanding the physics of tsunami wave generation and propagation, and in the creation of an effective tsunami warning system. The paper provides an overview of the history of tsunami recording in the open ocean from the beginning (about 50 years ago) to the present day. It describes modern tsunami monitoring systems, including the Deep-ocean Assessment and Reporting of Tsunamis (DART), innovative Japanese bottom cable projects, and the NEPTUNE-Canada geophysical bottom observatory. The specific peculiarities of seafloor longwave observations in the deep ocean are discussed and compared with those recorded in coastal regions. Tsunami detection in bottom presure observations is exemplified based on analysis of distant (22000 km) records of the 2004 Sumatra tsunami in the northeastern Pacific.     

Analysis of the necessity and possibility of tsunami early warning on the Black-Sea coast

The catastrophic tsunami of December 26, 2004 in Southeast Asia revealed the necessity of creating tsunami early warning systems in the regions of the World Ocean where these systems are still absent but the potential hazard of tsunami generation exists. The Black Sea is one of these regions. We present the general characteristic of the tsunami hazard in the Black-Sea region and describe the most probable zones of tsunami generation, the specific features of tsunami propagation, and the parameters of tsunamis according to the data of observations and the results of numerical simulations. We also discuss the possibility of tsunami early warning on the basis of the operative data provided by the network of hydrometeorological and seismological observation stations existing in this region. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 57–66, September–October, 2008.     

基于数值模拟的渤海海域地震海啸危险性定量化研究

根据地震海啸产生的条件,结合渤海海域的地形特征、地质构造、地震学特征和历史地震及海啸记录对渤海海域潜在的地震海啸进行了数值模拟研究。分析了渤海可能引发地震海啸的震源区域,讨论了渤海发生海啸灾害的可能性。文中通过数值模拟再现了渤海历史上几次规模较大的地震事件可能引发的海啸情景,研究分析了可能的地震海啸在渤海及周边海域的传播过程及波动特征.地震海啸传播模型采用基于四叉树原理的自适应网格加密技术,有效解决了局部分辨率与计算效率之间的矛盾。数值计算包括地震海啸产生及传播过程。利用该模型对渤海潜在的地震海啸进行了数值计算,基于数值计算结果定量阐述了渤海海域潜在地震海啸对渤海局部岸段及北黄海沿岸的影响,给出了渤海可能地震海啸危险性划分;研究结果将为我国海啸危险性分析和海啸预警技术研究工作提供技术支持。     

2010 年智利和2011 年日本地震海啸在我国东南沿岸诱导的波流特征及危险性分析

本文基于有限断层模型和OKADA 位错模型计算海表变形场作为初始条件,利用MOST 海啸数值模型模拟分析了2010年智利和2011 年日本地震海啸在我国东南沿海地区的海啸传播特征,海啸波模拟结果与观测数据吻合较好。重点研究分析了沈家门港口海域的海啸波流特征及其诱导的涡旋结构。研究结果表明：尽管两次事件的海啸源位置及破裂特征完全不同,但海啸波流在我国东南沿岸的分布特征大致相似;另外相对于海啸波幅而言,港湾中海啸流具有更强的空间差异性,港口入口、岬角地形处和岛屿间水道中往往会有强流存在。尽管这两次越洋海啸均未能在我国东南沿海引发淹没情形,但通过数值计算发现局部均存在超过3 m/s 以上的强流,因此进行海啸预警及风险管理时应综合考虑海啸波流的影响。