深圳海域潮汐海啸波耦合数值研究

以COMCOT海啸模式和TPXO7.1全球潮汐模式为基础,采用三层嵌套网格,建立了南海海啸与潮汐耦合计算模型,分析深圳海域海啸和潮汐相互作用。潮汐计算结果与实测数据吻合较好,高、低潮位平均误差小于15 cm,20 cm;在潮汐验证的基础上,以马尼拉海沟潜在地震海啸源为案例,进行8.0,9.0级地震海啸与潮汐耦合情景模拟计算,计算结果表明,9级地震海啸在深圳海域外海波高为140~150 cm,如先行波为正波发生在高潮时将产生异常高潮位,负波发生在低潮时将产生异常低潮位,线性叠加计算结果偏大,在25.0 cm之内,到达时间差异小于6 min。     

马尼拉俯冲带潜在地震海啸对华南沿海的影响

马尼拉俯冲带潜在地震海啸对我国南部沿海城市构成巨大威胁,利用情景式数值模拟技术重构灾害过程并评估危险等级有助于理解南海海啸传播规律并指导预警预报和防灾减灾工作。根据美国太平洋海洋环境研究中心(Pacific Marine Environmental Laboratory, PMEL)发布的马尼拉俯冲带断层参数设计M_w 7.5、M_w 8.1和M_w 8.5三个震级下共19个震源,应用非静压海啸数值模型(Non-hydrostatic Evolution of Ocean WAVE, NEOWAVE)模拟各震源激发海啸在南海海盆的传播过程,通过最大波辐和测点时间序列发现海啸波能量传输分布并评估代表区域危险等级。研究表明, M_w 7.5级地震海啸对我国南部沿海的影响较低,波幅一般不超过30 cm; M_w 8.1级地震海啸对华南沿海主要造成太平洋海啸预警中心定义的Ⅱ或Ⅲ级海啸危险等级,海啸影响范围和能量分布特征由震源位置决定; M_w 8.5级地震海啸主要对中国沿海构...     

A Record of Palaeo-Tsunami in the Indian Ocean

The history of catastrophic events on the Indian coast helps us to understand the frequency and magnitude of the tsunamis that occurred in the Indian Ocean. These catastrophic events have changed the coastal landscape and have left significant records for further studies. These rare events have occurred in the Indian Ocean. There have been megatsunamigenic events in the past due to volcanic eruptions and earthquakes. Those events due to earthquakes have proved more catastrophic than the volcanic activities. There has been limited official records of the causality and magnitude of palaeo-tsunamigenic events. These have been studied using the various proxies. The rate of sedimentation is a proportional tool to study the magnitude of a tsunami and this has proved to be a successful tool along with foraminiferal assemblages. Causes for a tsunami to occur are by and large, the subduction zone earthquakes of the Indian plate has been the most common source for tsunami in the Indian Ocean. More often the Andaman and Nicobar and the Indonesian islands have been vulnerable to tsunami than the mainland of India and Sri Lanka.

In summary, in the last 200 years at least three basin-wide tsunamis have occurred, with several smaller tsunami affecting one or more coastlines in the region. The December 2004 M-9 tsunami seems to have been the largest and most destructive in the last two centuries, suggesting most tsunami are likely to be smaller but still allowing the possibility that even larger tsunami could be generated in propitious circumstances.     

越洋海啸的数值模拟及其对我国的影响分析

简要介绍了地震海啸产生的物理机制、海啸波在大洋中的传播特性以及海啸所具有的超强破坏力可能引发的巨大灾害;概述了全球地震海啸发生的频率和太平洋区域历史海啸的时空分布;整理分析了我国沿海发生海啸的频次和空间分布。针对越洋海啸传播的特点,采用基于波浪追逐原理和自适应网格加密技术的海啸数值模型对1960智利海啸进行了数值模拟,将模拟的结果与历史记录进行了对比,验证了模型的可靠性。通过对数值模拟结果的分析,初步讨论了我国沿海地区越洋海啸的危险性,并定量阐述了越洋海啸对我国各海区的影响。     

The Kuril Earthquakes and tsunamis of November 15, 2006, and January 13, 2007: Observations,analysis, and numerical modeling

Major earthquakes occurred in the region of the Central Kuril Islands on November 15, 2006 (M _w = 8.3) and January 13, 2007 (M _w = 8.1). These earthquakes generated strong tsunamis recorded throughout the entire Pacific Ocean. The first was the strongest trans-Pacific tsunami of the past 42 years (since the Alaska tsunami in 1964). The high probability of a strong earthquake (M _w ≥ 8.5) and associated destructive tsunami occurring in this region was predicted earlier. The most probable earthquake source region was investigated and possible scenarios for the tsunami generation were modeled. Investigations of the events that occurred on November 15, 2006, and January 13, 2007, enabled us to estimate the validity of the forecast and compare the parameters of the forecasted and observed earthquakes and tsunamis. In this paper, we discuss the concept of “seismic gaps,” which formed the basis for the forecast of these events, and put forward further assumptions about the expected seismic activity in the region. We investigate the efficiency of the tsunami warning services and estimate the statistical parameters for the observed tsunami waves that struck the Far Eastern coast of Russia and Northern Japan. The propagation and transformation of the 2006 and 2007 tsunamis are studied using numerical hydrodynamic modeling. The spatial characteristics of the two events are compared.     

日本南海海槽地震海啸对我国东海沿岸影响

本文利用数值模拟技术重现了1707年宝永地震海啸的传播过程,定量分析了我国东海沿岸海啸时空分布特征。计算结果表明,地震发生2.5小时后海啸波传至东海陆架,震后6小时浙江沿海地区遭到海啸的袭击,沿岸最大海啸波高为0.8米。通过海啸波在东海大陆架传播时海底地形与波幅的关系,研究分析了东海陆架缓变地形下海啸放大效应,为及时判断沿海可能的海啸强度和受灾程度提供了便捷的估算方法。此外,本文还评估了南海海槽发生极端地震时,中国东海沿岸的海啸危险性,为东海区域针对日本南海海槽进行海啸预警和减灾评估提供定量科学的参考。     

海啸预警与第四纪古海啸沉积记录研究进展

海啸对人类的生命和财产安全构成巨大的威胁,2004年12月26日苏门答腊特大海啸的发生,引起了国际社会对海啸预警问题的重视,并进一步认识到古海啸沉积研究的重要性.介绍了国际上对海啸预警和古海啸沉积研究的进展,重点综述古海啸沉积的研究现状、研究方法与识别标志.最近20年来,研究者们着重对滨岸、浅海或陆地上的现代海啸沉积和古海啸堆积物进行研究,而对深水区域的古海啸记录研究很少.笔者认为在海啸多发海域的深水区进行长柱状沉积物取样,通过沉积学和地球化学分析研究,把古海啸沉积从海底正常沉积中识别出来,再结合定年,有助于恢复古海啸史,明确长期的灾害风险.     

Underwater observations of the giant spoon worm <Emphasis Type="Italic">Ikeda taenioides</Emphasis> (Annelida: Echiura: Ikedidae) in a subtidal soft-bottom environment in northeastern Japan,which survived tsunamis of the 2011 off the Pacific Coast of Tohoku Earthquake

Tsunamis associated with the 2011 off the Pacific Coast of Tohoku Earthquake seriously disrupted the shallow marine ecosystem along a 2000 km stretch of the Pacific coast of Japan. The effects of the 2011 tsunamis on the soft-bottom benthic community have been relatively well studied in the intertidal zone, whereas tsunami effects on the subtidal benthos remain poorly understood. Here, we investigated populations of the world’s largest spoon worm Ikeda taenioides (Annelida: Echiura: Ikedidae) in subtidal zone of Funakoshi Bay, Tohoku District, northeastern Japan. Subtidal scuba-diving surveys at two sites in the bay showed extremely long proboscises frequently extending from small holes in the sandy seafloor shortly before and soon after the tsunami disturbances. Based on morphological and molecular identification, the proboscises were revealed to be parts of I. taenioides. On 30 November 2011, 265 days after the tsunami event, many large-sized individuals with >1 m long proboscises were observed; these individuals were probably not derived from post-tsunami larval recruitment but more likely survived the tsunami disturbances. This is surprising because other sympatric megabenthos (e.g. spatangoid echinoids and venerid bivalves) and seagrass beds were almost completely destroyed (although they later recovered) by the tsunamis in this bay. The burrows of I. taenioides are known to be very deep (70–90 cm), which may have sheltered them from the impacts of the tsunamis. Our observations suggest that the effects of the 2011 tsunamis on benthos in soft sediments may differ depending on their burrowing depth.     

海上丝绸之路海啸灾害危险分析

海上丝绸之路不仅是商业和贸易的通道, 也是东西方文化友谊的道路。2004年印度洋海啸对丝路沿线的多个沿海国家造成了重大破坏。因此需要对海啸发生规律和危害进行分析, 以确保海上丝绸之路上经济和文化交流的安全。为探索和识别海上丝绸之路上的海啸灾害, 本文给出了历史海啸事件的特征和规律。从震源震级、震源深度和水深等震源参数中发现了一些历史海啸数据背后的有用信息。本文还探讨了不同震级引起海啸的概率问题。分析结果表明：海上丝绸之路上的海啸主要发生在8个主要构造断层, 每个断层都有不同的海啸发生规律。在统计分析的基础上, 本文采用数值模型模拟了海上丝绸之路沿岸的潜在海啸,计算结果展示了海上丝绸之路沿岸的潜在海啸灾害程度。本文的研究成果有助于海啸灾害预警, 能够为保证海上丝绸之路贸易交流的安全提供科学参考。     

Positioning requirements for the tsunami warning system

Abstract

Canada has increased the number of tsunami warning stations on the Pacific Coast from two to three. The last gauge was installed at the north end of Vancouver Island, thereby filling a large gap previously existing and providing full coverage along the coast. The record of gauges at two of the three locations is accessible either by telephone or by means of meteor burst communication, alleviating the difficulties experienced during the tsunami threat of May 6, 1986, when telephone communications were disrupted by heavy use. The gauge at Langara Island will be relocated in a more accessible and also a more tsunami‐responsive location at Rennell Sound in the Queen Charlotte Islands. All tsunami gauges also serve as tide gauges, recording the water level every 15 min. In the event of a tsunami, the recording interval can be altered to every 60 s. Suggestions have been made that Canada attempt deep‐sea recording of tsunamis off its Pacific Coast. Although this would be of great scientific value, no such program is contemplated at this time.     

The tsunami hypothesis—comparisons of the field evidence against the effects, on the Western Australian coast, of some of the most powerful storms on Earth

The tsunami hypothesis proposes that prehistoric tsunamis may have been larger than historic ones along coasts normally (historically) not associated with major tsunamis. The evidence for the hypothesis rests with the types of unusual sedimentary deposits and erosional forms along coasts where the largest historic and prehistoric storm waves do not appear capable of forming the features. This is especially the case at locations where boundary conditions, i.e. offshore water depth, coastal geomorphology and meteorological limitations, are not conducive to the propagation of sufficiently large storm waves at the shore. The tsunami hypothesis has been barely debated in the literature. This is despite the view of some, who suggest that storms have been overlooked, or underestimated, as a cause. Few comparisons have been made of the supposed tsunami generated features and the impacts on coasts of extreme intensity storms. Four of the most powerful tropical cyclones anywhere in the world in recent times struck the Western Australian coast between 1999 and 2002. The results of post-event surveys of these storms showed that none of them produced the enigmatic forms attributed elsewhere to tsunamis.     

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。     

Numerical simulation of the action of distant tsunamis on the Russian Far East coast

Results of a numerical simulation of the action of distant tsunamis on the coast of the Russian Far East are presented. It is shown that waves generated by focuses of the strongest M9 earthquakes in the region of South Chilean coast, as well as in the region of Papua New Guinea and Solomon Islands, are most dangerous for this coast. Other tsunamigenic zones of the Pacific Ocean, by virtue of their geographical position, orientation of focuses, and absence of pronounced channels (submarine ridges) along paths of tsunami propagation are not dangerous for it even at a limit magnitude of submarine subduction earthquakes. The simulation results are compared with historical data about manifestations of distant tsunamis on the Russian Far East coast.     

Scenarios of local tsunamis in the China Seas by Boussinesq model

The Okinawa Trench in the East China Sea and the Manila Trench in the South China Sea are considered to be the regions with high risk of potential tsunamis induced by submarine earthquakes. Tsunami waves will impact the southeast coast of China if tsunamis occur in these areas. In this paper, the horizontal two-dimensional Boussinesq model is used to simulate tsunami generation, propagation, and runnp in a domain with complex geometrical boundaries. The temporary varying bottom boundary condition is adopted to describe the initial tsunami waves motivated by the submarine faults. The Indian Ocean tsunami is simulated by the numerical model as a validation case. The time series of water elevation and runup on the beach are compared with the measured data from field survey. The agreements indicate that the Boussinesq model can be used to simulate tsunamis and predict the waveform and runup. Then, the hypothetical tsunamis in the Okinawa Trench and the Manila Trench are simulated by the numerical model. The arrival time and maximum wave height near coastal cities are predicted by the model. It turns out that the leading depression N-wave occurs when the tsunami propagates in the continental shelf from the Okinawa Trench. The scenarios of the tsunami in the Manila Trench demonstrate significant effects on the coastal area around the South China Sea.     

Effect of the Bottom Topography on Tsunami Propagation in the East （Japan） Sea

A study of tsunami events in the East （Japan） Sea using continuous Galerkin finite element model, aiming at reproducing tsunami waves generated by underwater earthquakes in 1983 and 1993 respectively has been performed focusing on the geographic extent of a topographic feature in the East （Japan） Sea. Numerical models can be the proper tools to study the combined effects of realistic topography. Subsequently, using the FEM based two-dimensional model we have simulated the smoothed and flattened topographic effects by removal of Yamato Rise and seamounts for the cases of tthe 1983 Central region earthquake tsunami and the 1993 southwestern Hokkaido earthquake tsunami. The results have shown that there will be higher tsunamis along the eastern coasts of Korea in general except some areas, like Sokcho with removal of topographic highs, thus providing complicated bottom topography of the East （Japan） Sea as effective tsunami energy scattering.     

从2011 海啸演习看中国海啸危害

2011 年11 月, 联合国教科文组织政府间海洋学委员会(IOC/UNESCO)发起了代号为“Exercise Pacific Wave 11”的跨国海啸演习, 演习区域为整个太平洋海区。中国应邀参加了本次演习, 演习在我国海域地震带上假设了两个震源, 分别位于琉球海沟和马尼拉海沟。为了评估这两个潜在海啸对我国的影响, 本文采用数值模拟的方式, 对其进行了计算。计算结果表明: 这两处震源所引发的海啸均能对我国造成灾害性影响, 受影响严重的省市有江苏、上海、浙江、福建、广东和海南等; 从传播时间图上看, 若发生大海啸, 海啸波将在5 h 内, 陆续影响沿海各省市; 相比琉球海沟, 马尼拉海沟震源产生的海啸会更快到达我国沿岸。     

Numerical Simulation of Tsunamis on the Tamil Nadu Coast of India

The State of Tamil Nadu was the most affected region in India during the tsunami of December 26, 2004, in the Indian Ocean, in terms of loss of life and damage. Numerical simulation was made for three tsunamis, the December 26, 2004, event, the Sumatra tsunami of 1833, and a hypothetical tsunami originating in the Andaman-Nicobar region. Since inundation is not included in these simulations, the tsunami amplitudes were deduced at the 10m depth contour in the ocean, off several locations on the coast of Tamil Nadu. The computed amplitudes appear reasonable as compared to known tsunami amplitudes from past events.     

Sediment grains moved by passing tsunami waves: Tsunami deposits in deep water

Tsunamis propagating in the open ocean have associated horizontal particle velocities that do not change with depth — yet the limiting water depth where a tsunami of given characteristics will initiate sediment motion remains unknown. Based upon linear wave theory and a parametrization of the Shields curve, equations are derived and solved, using an iterative scheme, to address the topic of grain movement by tsunami waves as a function of water depth and wave amplitude. The focus is on waves in deep water where tsunami waves behave linearly and on non-cohesive sediment grains. Furthermore, the question is addressed of which grain sizes are picked up on a sloping beach as the wave shoals. According to the results, even the Boxing Day tsunami in 2004 was incapable of moving fine sand in water deeper than 985 m in the Bay of Bengal and 335 m in the Indian and Pacific oceans. The results suggest that tectonic tsunamis of size equal to or smaller than the Boxing Day tsunami cannot initiate motion of deep-water cohesionless sediments that can be correlated on an oceanic basin-wide scale.     

Tsunamis in the central part of the Caspian Sea

This paper describes the geotectonics of the Caspian Sea basin and the seismicity of its central part. The seismicity analysis enables us to identify the most probable zones of tsunami generation. We also present a brief review of the historical records of tsunamis in the Caspian Sea. In order to estimate the tsunami risk, we used the method of numerical hydrodynamic simulation while taking into account the real topography of the Caspian Sea. The computation of the wave field for the possible tsunamis occurring in the central part of the Caspian Sea allowed us to estimate the maximum expected heights of the waves along the coast of the CIS countries (Russia, Azerbaijan, Kazakhstan, and Turkmenistan). On the basis of the earthquake statistics in the region and the results of numerical experiments, we show that the extreme wave heights can reach 10 m at certain parts of the coast. Such extreme events correspond to extended (up to 200 km) seismic sources with M _S ～ 8 and a recurrence period of T ≈ 1600 years. The tsunami wave heights are expected to be as high as 3 m for sources of lesser extent (<50 km) with earthquake magnitudes of M _S ～ 7 and a recurrence period of 200 years.     

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。