全球海啸灾害事件统计及预警系统简述

统计分析了全球历史海啸灾害数据,结合相关海啸研究成果,给出了全球海啸的分布特点及历史重大事件,并介绍了全球海啸预警系统、数值技术以及海啸监测等防灾情况。     

海洋微塑料来源、分布及生态效应研究进展

微塑料广泛分布于世界范围内的大洋和近海海域。作为新兴的污染物,微塑料对海洋生态环境威胁巨大。微塑料可以直接或间接被海洋动物摄入,导致其生长减缓或停滞、繁殖被抑制、寿命减短、进食量降低、耗氧量以及酶活性改变。微塑料与海洋浮游植物相互作用会对其生长、光合作用、氧化应激能力等产生影响。然而,微塑料对海洋浮游植物的致毒机理尚未完全明朗,还需更多的相关研究以探明其毒性效应机制。为保护海洋环境安全,更好的治理微塑料污染问题,有必要加强微塑料的相关研究,同时采取一系列有力的政策法规来监管塑料及微塑料的使用。     

中国的海啸灾害危险性及海啸预警系统——解读2011年太平洋海啸演习

新世纪以来频发的海啸灾害引起了国际社会的广泛关注,各滨海国家不仅加大了在海啸预警建设和海啸灾害危险性、海啸基础理论研究方面的投入,更进一步加强了国际社会在应对海啸灾害方面交流与合作.为测试太平洋各国海啸预警系统的有效性以及政府职能部门的应急管理能力,切实提高各国区域和局地海啸的应对水平,促进国家和地区间海啸预警的交流与合作,联合国教科文组织政府间海洋学委员会(IOC/UNESCO)决定2011年11月9-10日,在整个太平洋地区举行一次代号为“Exercise Pacific Wave 11”的海啸演习.此次演习恰逢日本“3.11”大地震海啸发生后的8个月,通过本次演习对督促太平洋各国进一步检验本国的海啸预警系统、评估本国的海啸危险性均有着重要的意义.中国作为IOC和太平洋海啸预警系统的成员国,积极组织实施了我国历史上第一次涉及当地人员疏散的海啸演习.本文将在本次演习所涉及的海啸源评估、海啸数值计算的基础上,应用新的海啸灾害分级标准对我国沿海的海啸危险性和海啸预警系统进行重新评估分析,期望本文的研究将为今后的海啸预警及海啸灾害评估工作提供科学的决策依据标准.     

Laboratory-scale generation of tsunami and long waves

Physical modeling of long waves in laboratories is still a valuable and trustworthy option to study long wave propagation, run-up and near-shore dynamics, and complex nonlinear interactions of approaching wave and macroroughness elements on the shore. Yet, problems develop if full-scale measured time series of real tsunami or numerically derived time series are to be adequately modeled in a timewise meaningful and scaled experiment. Hence, an in-depth review of the state-of-the-art long wave generation methods in laboratory wave flumes and basins is conducted. The study reveals that improved laboratory techniques could significantly contribute to enhance the accuracy and applicability of experimental tests. This would give important information on the interaction between the shoreline and infrastructures on land in order to deduce valuable information on the topic of tsunami inundation processes or wave-induced impacts on houses. In this light, a novel wave generation technique using high-capacity pipe pumps under some control and a loop-feedback control is meticulously developed and discussed. The wave generation facility is successfully tested for single sinusoidal leading depression waves as well as for prolonged solitary and leading depression N-waves of varying duration. The long wave generation technique is further assessed in terms of its capability to generate long waves abstracted from prototype conditions. The influence of controller settings on the resulting waves is discussed.     

Reconstructing tsunami run-up from the characteristics of tsunami deposits on the Thai Andaman Coast

Tsunamis can leave deposits on the land surface they inundate. The characteristics of tsunami deposits can be used to calculate tsunami run-up height and velocity. This paper presents a reconstruction of tsunami run-up from tsunami deposit characteristics in a simple mathematical model. The model is modified and applied to reconstruct tsunami run-ups at Ao Kheuy beach and Khuk Khak beach, Phangnga province, Thailand. The input parameters are grain-size and maximum run-up distance of the sediment. The reconstructed run-up heights are 4.16–4.91 m at Ao Kheuy beach and 5.43–9.46 m at Khuk Khak beach. The estimated run-up velocities (maximum velocity) at the still water level are 12.78–19.21 m/s. In the area located 70–140 m inland to the end of run-up inundation, estimated mean run-up velocities decrease from approximately 1.93 m/s to 0 m/s. Reasonably good agreements are found between reconstructed and observed run-up heights. The tsunami run-up height and velocity can be used for risk assessment and coastal development programs in the tsunami affected area. The results show that the area from 0 to 140 m inland was flooded by high velocity run-ups and those run-up energies were dissipated mainly in this area. The area should be designated as either an area where settlement is not permitted or an area where effective protection is provided, for example with flood barriers or forest.     

滑坡海啸的预测模型及其应用

对3个典型的滑坡海啸强度的预测模型进行了介绍,并将其与海底边坡稳定性分析相结合,提出了滑坡海啸的预测方法。采用滑坡海啸预测方法计算了岙山原油码头潜在滑坡区滑坡海啸的强度,结果表明,若该地区发生滑坡,局部海岸将会产生波高为2~3 m的海啸,与当时观测到结果相吻合,因而该预测方法是具有一定准确性的较好预测海啸强度的方法。     

Deep water signature of a tsunami

The dynamics of tsunamis can be divided, for convenience, into three parts: tsunami generation, tsunami propagation, and the coastal problems. Out of these three, the problem of tsunami propagation is probably better understood than the other two. One of the main hindrances to the quantitative prediction of tsunami amplitudes at various coastal locations is a lack of detailed knowledge about the deep water signature of a tsunami. Here, the present understanding of this problem is discussed.     

The tsunami of 3 February 1605

Whether the origins of the tsunami of 3 February 1605 were separated ones or a joined one, is one of the most important problems for Japanese society. When the marine knowledge has not been popularized, it has been considered that the damage pattern on Hachijo Island (including Kojima) was an important key to solving this question.It resembles the situation that the reports concerning the tsunami of 1 April 1946 were introduced to Japanese society under an internal disturbance just after the war, and we overlooked the most important consideration on the combination of tsunami and storm waves caused by the trade wind, and received this tsunami as an extraordinarily huge one.We studied the statistics of recent wind directions around Hachijo Island in January and February 1973, 1974, 1977, 1983, 1984, 1985, 1986 and 1987. And we believed that the probability was high that we could explain well that the damage pattern on Hachijo Island in 1605 was due to the combination of tsunami and storm waves caused by the monsoon.We need not, therefore, look back the damage pattern on Hachijo Island when we consider the fact that the necrologies of many temples in Shizuoka Prefecture record no death on 3 February 1605, proves to be the key to infer that the origins were separated ones.     

On local probability of invasive tsunami

Abstract

Tsunami occurrence and invasive tsunami at a local area in the circum‐Pacific seismic zone were studied as a Poisson process. The tsunami height at Osaka, Japan, was related to tsunami magnitude. The exceedence frequency of invaded tsunami at Osaka showed a good fitness to the Poisson process. However, an adapted process should be introduced for exceedence frequency of tsunami occurrence in the western Pacific. The exceedence probability of invasive tsunami at Osaka was shown as a function of tsunami magnitude on a diagram with a parameter of the time period. The obtained result might be useful for the planning of coastal area, warning of invasive tsunami, and designing coastal structures as protection within the scope of tsunami economics.     

2015年春季长江口表层沉积物生源要素分布和来源

根据2015年5月对长江口及其邻近海域的生态环境调查资料, 探讨长江口春季表层沉积物总有机碳(TOC)、总氮(TN)、总磷(TP)和生源硅(BSi)4类生源要素的空间分布和来源。结果表明: 2015年春季长江口表层沉积物TOC、TN、TP和BSi平均含量分别为0.315%、0.041%、0.066%和0.450%, 其中, 沉积物中TOC、TN受到陆源输入和海洋自生输入双重影响, 且海洋自生组分的贡献较大, 二者空间分布均呈现南部分布最高并沿西北方向递减趋势; TP分布主要受陆源输入影响, 并呈西北向东南递减趋势; BSi来源于生物沉积, 总体呈现南部高、北部低的分布趋势。与2007年相比, 长江口表层沉积物有机碳、氮含量降低, 东南外海区域替代浑浊区域成为表层沉积物生源要素含量最高区域, 且陆源输入对长江口表层沉积物生源要素的贡献趋于减弱。     

Predicting tsunami arrivals: Estimates and policy implications

Tsunami is one of a few kinds of natural disasters that leave people some time for escape. This escape time, which is essentially the time for the giant wave to propagate from the epicentre to a coast, has to be estimated without delay upon the occurrence of the incident. With the advancement of water wave theories, much work has been done to model the propagation of tsunamis from deep oceans to shallow water. The authors argue that while much emphasis has been put on the expansion of the high-tech early warning system and the development of complicated tsunami models, a simple-to-use yet accurate predictive model is still wanting. This paper presents a handy linear wave model, which is capable of estimating the arrival time of a tsunami with very good accuracy, as has been verified by comparison with past incidents. With the availability of such a simple model, even local communities without access to a high-tech warning system can readily estimate the time left for emergency evacuation.     

美国夏威夷州海啸灾害研究概述

夏威夷是世界上最易遭受海啸洪水灾害的地区之一。本文介绍了美国夏威夷群岛在海啸实时监测和数值模拟方面的研究进展,并重点介绍了夏威夷海啸预警系统的组成与作用。     

海啸地震震源机制解统计

为探索海啸地震发震时的规律,统计分析了1976-2010年的美国全球CMT地震矩心矩张量数据,并结合美国海洋与大气局的海啸灾害数据库,从海啸事件和较大海啸事件两个方面对震源机制解展开了对比统计分析,给出了海啸地震在震源方面的统计特征。     

Rationale for measurement of midocean tsunami signature

Abstract

Arguments are presented to justify midocean tsunami measurements and related investigations aimed toward improvement of tsunami prediction and warning. It is postulated that midocean tsunami signatures be measured simultaneously at several locations and correlated with high‐accuracy onshore measurements.     

Spatiotemporal distributions and environmental drivers of diversity and community structure of nosZ-type denitrifiers and anammox bacteria in sediments of the Bohai Sea and North Yellow Sea,China

Denitrification and anammox processes are major nitrogen removal processes in coastal ecosystems. However, the spatiotemporal dynamics and driving factors of the diversity and community structure of involved functional bacteria have not been well illustrated in coastal environments, especially in human-dominated ecosystems. In this study, we investigated the distributions of denitrifiers and anammox bacteria in the eutrophic Bohai Sea and the northern Yellow Sea of China in May and November of 2012 by constructing clone libraries employing nosZ and 16S rRNA gene biomarkers. The diversity of nosZ-denitrifier was much higher at the coastal sites compared with the central sites, but not significant among basins or seasons. Alphaproteobacteria were predominant and prevalent in the sediments, whereas Betaproteobacteria primarily occurred at the site near the Huanghe (Yellow) River estuary. Anammox bacteria Candidatus Scalindua was predominant in the sediments, and besides, Candidatus Brocadia and Candidatus Kuenenia were also detected at the site near the Huanghe River estuary that received strong riverine and anthropogenic impacts. Salinity was the most important in structuring communities of nosZ-denitrifier and anammox bacteria. Additionally, anthropogenic perturbations (e.g. nitrogen overloading and consequent high primary productivity, and heavy metal discharges) contributed significantly to shaping community structures of denitrifier and anammox bacteria, suggesting that anthropogenic activities would influence and even change the ecological function of coastal ecosystems.     

On the numerical modeling of tsunami wave generation and propagation

Abstract

In this article three main stages of tsunami wave evolution are investigated. At first, the development of disturbances from a given patched elevation of the bottom surface in an incompressible nonviscous fluid of the uniform depth is considered. Then, a tsunami wave diffraction by underwater bottom elevation or cavity is investigated. In this case the shallow water equations are already used, and it is supposed that a cylindrical wave is spread from patched water elevation over the epicentrum. Last, the tsunami propagation and transformation in a shallow water region and its run‐up on a beach are investigated on the basis of the improved shallow water theory, taking into consideration the nonlinear and dispersive terms of higher order. The proposed theory is tested in a problem of collisions of two solutions. Solutions of the first and the second problems are obtained by the method of integral Laplace's transformation with following numerical inversion of transformations. A finite difference method for a solution of the last problem is used.     

Temporal variability of tsunami arrival detection distance revealed by virtual tsunami observation experiments using numerical simulation and 1-month HF radar observation

The combination of a high-frequency ocean surface radar and a tsunami detection method should be assessed as the onshore-offshore distribution of tsunami detection probability, because the probability will vary in accordance with the signal-to-noise ratio (SNR) and the tsunami magnitude in addition to the radar system specifications. Here, we statistically examine the tsunami detection distance based on virtual tsunami observation experiments by using signals received by a high-frequency radar in February 2014 installed on the southern coast of Japan and numerically simulated velocities induced by a Nankai Trough earthquake. In the experiments, the Doppler frequencies associated with the simulated velocities were superimposed on the receiving signals of the radar, and the radial velocities were calculated from the synthesized signals by the fast Fourier transform. Tsunami arrival was then detected based on the temporal change in the cross-correlation of the velocities, before and after tsunami arrival, between two points 3 km apart along a radar beam. We found that the possibility of tsunami detection primarily depends on the kinetic energy ratio between tsunami current and background current velocities. The monthly average detection probability is over 90% when the energy ratio exceeds 5 (offshore distance: 9 km ≤ L ≤ 36 km) and reduces to 50% when the energy ratio is approximately 1 (L = 42 km) over the shelf slope. The ratio varied with the background current physics and SNR, which was mainly affected by ocean surface wave heights and ionospheric electron density.     

New buoy observation system for tsunami and crustal deformation

We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication.     

Estimation of the offshore form of tsunami waves

Estimation of the offshore form of tsunami waves based on an observed tidegage record at a bay head is attempted by means of an impulse response method and a characteristics method. For several tsunamis in Onagawa Bay, the results estimated by both methods are compared with the observed data at an offshore station. The correlation coefficient between the estimated and the observed values is 0.9 to 0.95, and the present methods are proved to be practical. The validity of the characteristics method is further confirmed in the case of Ofunato Bay.