Truncated dunes as evidence of the 2004 tsunami in North Sumatra and environmental recovery post‐tsunami

The 2004 tsunami transformed the coast of Indonesia. This research investigates a sand dune area in Lampuuk, Sumatra, that was scoured by tsunami flow. We assessed geomorphology one‐year post‐event and examine the timescale of vegetation recovery. Ground Penetrating Radar (GPR) evidence shows an eroded succession of thin dipping units, overlain by aeolian layers 0 to 50 cm thick. Incipient dunes were absent, indicating limited dune rebuilding at one‐year post‐tsunami, possibly resulting from channelised airflow and the absence of vegetation. Recolonisation by vegetation was initially limited but progressed rapidly between 2005 and 2011, highlighting the temporal non‐linearity of recovery processes.     

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。     

Earthquake, strong tide and global low temperature

＂La Madre＂ is a kind of upper atmospheric air current, and occurs as ＂warm phase＂ and ＂cold phase＂ in the sky of Pacific Ocean alternately. There exists this phenomenon, called ＂Oscillation Decade in the Pacific＂ （ODP）, for 20 - 30 years. It is concerned with 60 year cycle of the tides. Lunar oscillations explain an intriguing 60-year cycle in the world＇s temperature. Strong tides increase the vertical mixing of water in the oceans, drawing cold ocean water from the depths to surface, where it cools the atmosphere above. The first strong seismic episode in China was from 1897 to 1912; the second to the fifth was the in 1920-1937, 1946-1957, 1966-1980, 1991-2002, tsrectruely. The alternative boundaries of＂La Madre＂ warm phase and cold phase were in 1890, 1924, 1946 and 2000, which were near the boundaries of four strong earthquakes. It indicated the strong earthquakes closedly related with the substances＇ motion of atmosphere, hydrosphere and lithosphere, the change of gravity potential, and the exchange of angular momentum. The strong earthquakes in the ocean bottom can bring the cool waters at the deep ocean up to the ocean surface and make the global climate cold. the earthquake, strong tide and global low temperature are close inrelntion for each othen.     

全球海啸地震震源机制解及海啸成因探讨

海啸作为五大海洋自然灾害之一,严重威胁着人类生命财产安全。近些年来,国内外学者对地震海啸进行了大量研究,主要针对海啸的生成、传播、爬高和淹没的数值模拟,以及古海啸沉积物进行研究,但是对于海啸地震震源机制的研究还比较欠缺,尤其是缺乏对震级小于6.5的海啸地震的研究。针对我国的地震海啸研究现状,强调震级小于6.5地震引发海啸的问题不容忽视。本文归纳整理了全球766次地震海啸,利用三角图分类基本法则对海啸地震震源机制解进行分类,并对其中341个发生在1976年后的海啸地震进行震源机制解分析,对其中633次海啸浪高进行统计学方法分析研究。本文认为逆冲型、正断型、走滑型和奇异型机制地震均能引发海啸,逆冲型地震引发的海啸占比最大,震级小于6.5级地震引发的海啸的浪高也有高达10 m的情况,也能产生巨大破坏性。逆冲型、正断型、奇异型地震可直接引起海底地形垂向变化,进而引发海啸,而走滑型地震引发海啸则可能有两种原因,一种是走滑型地震并非纯走滑型而是带有正断或逆冲分量从而引发海啸,另外一种是走滑型地震引发海底滑坡导致海底地形变化进而产生海啸。从海啸地震震源深度分析,能产生海啸的地震震源深度97%以上都是浅源地震,主要集中在30 km深度以内,但是也有中深源地震海啸。本文综合海啸地震的震源特点、我国地理位置以及以往海啸发生的情况,认为未来我国沿海地区威胁性的地震海啸主要集中在马尼拉海沟和台湾海峡区域,在今后海啸预警方面需要格外重视这些区域,通过建立完善海啸预警系统来减少损失。     

Planning for Tsunami-Resilient Communities

The National Tsunami Hazard Mitigation Program (NTHMP) Steering Committee consists of representatives from the National Oceanic and Atmospheric Administration (NOAA), the Federal Emergency Management Agency (FEMA), the U.S. Geological Survey (USGS), and the states of Alaska, California, Hawaii, Oregon, and Washington. The program addresses three major components: hazard assessment, warning guidance, and mitigation. The first two components, hazard assessment and warning guidance, are led by physical scientists who, using research and modeling methods, develop products that allow communities to identify their tsunami hazard areas and receive more accurate and timely warning information. The third component, mitigation, is led by the emergency managers who use their experience and networks to translate science and technology into user-friendly planning and education products. Mitigation activities focus on assisting federal, state, and local officials who must plan for and respond to disasters, and for the public that is deeply affected by the impacts of both the disaster and the pre-event planning efforts. The division between the three components softened as NTHMP scientists and emergency managers worked together to develop the best possible products for the users given the best available science, technology, and planning methods using available funds.     

A Tsunami Generated by a Possible Submarine Slide: Evidence for Slope Failure Triggered by the North Anatolian Fault Movement

A tsunamigenic sediment layer has been discovered in fluvio-alluvial sequences on the northern coast of the Marmara Sea, northwestern Turkey. The layer consists of unsorted silty coarse sand including terrestrial molluscs and charcoal fragments. The AMS radiometric ages of the shells have been estimated at around BC 400, AD 300, AD 400, and AD 1000. We propose that a tsunami occurred in the Marmara Sea in the middle of 11th century and invaded the fluvial plains. The older fossils were derived from the underlying horizons, and it is probable that buoyant materials such as terrestrial molluscs and charcoals were isolated from liquefied sediments during submarine sliding. Slope failure of coastal blocks triggered by fault movement generated tsunamis, which might have transported floating materials to the backshore.     

The Role of Education in the National Tsunami Hazard Mitigation Program

Tsunami education activities, materials, and programs are recognized by the National Tsunami Hazard Mitigation Program (NTHMP) as the essential tool for near-source tsunami mitigation. Prior to the NTHMP, there were no state tsunami education programs outside of Hawaii and few earthquake education materials included tsunami hazards. In the first year of the NTHMP, a Strategic Plan was developed providing the framework for mitigation projects in the program. The Strategic Plan identifies education as the first of five mitigation strategic planning areas and targets a number of user groups, including schools, businesses, tourists, seasonal workers, planners, government officials, and the general public. In the 6 years of the NTHMP tsunami education programs have been developed in all five Pacific States and include print, electronic and video/film products, curriculum, signage, fairs and workshops, and public service announcements. Multi-state education projects supported by the NTHMP include TsuInfo, a bi-monthly newsletter, and Surviving a Tsunami, a booklet illustrating lessons from the 1960 Chilean tsunami. An additional education component is provided by the Public Affairs Working Group (PAWG) that promotes media coverage of tsunamis and the NTHMP. Assessment surveys conducted in Oregon, Washington, and Northern California show an increase in tsunami awareness and recognition of tsunami hazards among the general population since the NTHMP inception.     

Volcanic and Scientific Activity at Kick ’em Jenny Submarine Volcano 2001–2002: Implications for Volcanic Hazard in the Southern Grenadines,Lesser Antilles

Kick em Jenny submarine volcano, ~8 km north of Grenada, has erupted at least 12 times since it was first discovered in 1939, making it the most frequently active volcano in the Lesser Antilles arc. The volcano lies in shallow water close to significant population centres and directly beneath a major shipping route, and as a consequence an understanding of the eruptive behaviour and potential hazards at the volcano is critical. The most recent eruption at Kick em Jenny occurred on December 4 2001, and differed significantly from past eruptions in that it was preceded by an intensive volcanic earthquake swarm. In March 2002 a multi-beam bathymetric survey of the volcano and its surroundings was carried out by the NOAA ship Ronald H Brown. This survey provided detailed three-dimensional images of the volcano, revealing the detailed morphology of the summit area. The volcano is capped by a summit crater which is breached to the northeast and which varies in diameter from 300 to 370 m. The depth to the summit (highest point on the crater rim) is 185 m and the depth to the lowest point inside the crater is 264 m. No dome is present within the crater. The crater and summit region of Kick em Jenny are located at the top of an asymmetrical cone which is about 1300 m from top to bottom on its western side. It lies within what appear to be the remnants of a much larger arcuate collapse structure. An evaluation of the morphology, bathymetry and eruptive history of the volcano indicates that the threat of eruption-generated tsunamis is considerably lower than previously thought, mainly because the volcano is no longer thought to be growing towards the surface. Of more major and immediate concern are the direct hazards associated with the volcano, such as ballistic ejecta, water disturbances and lowered water density due to degassing.     

The U.S. National Tsunami Hazard Mitigation Program: A Successful State–Federal Partnership

The U.S. National Tsunami Hazard Mitigation Program (NTHMP) is a State/Federal partnership created to reduce tsunami hazards along U.S. coastlines. Established in 1996, NTHMP coordinates the efforts of five Pacific States: Alaska, California, Hawaii, Oregon, and Washington with the three Federal agencies responsible for tsunami hazard mitigation: the National Oceanic and Atmospheric Administration (NOAA), the Federal Emergency Management Agency (FEMA), and the U.S. Geological Survey (USGS). In the 7 years of the program it has, 1. established a tsunami forecasting capability for the two tsunami warning centers through the combined use of deep ocean tsunami data and numerical models; 2. upgraded the seismic network enabling the tsunami warning centers to locate and size earthquakes faster and more accurately; 3. produced 22 tsunami inundation maps covering 113 coastal communities with a population at risk of over a million people; 4. initiated a program to develop tsunami-resilient communities through awareness, education, warning dissemination, mitigation incentives, coastal planning, and construction guidelines; 5. conducted surveys that indicate a positive impact of the programs activities in raising tsunami awareness. A 17-member Steering Group consisting of representatives from the five Pacific States, NOAA, FEMA, USGS, and the National Science Foundation (NSF) guides NTHMP. The success of the program has been the result of a personal commitment by steering group members that has leveraged the total Federal funding by contributions from the States and Federal Agencies at a ratio of over six matching dollars to every NTHMP dollar. Twice yearly meetings of the steering group promote communication between scientists and emergency managers, and among the State and Federal agencies. From its initiation NTHMP has been based on the needs of coastal communities and emergency managers and has been results driven because of the cycle of year-to-year funding for the first 5 years. A major impact of the program occurred on 17 November 2003, when an Alaskan tsunami warning was canceled because real-time, deep ocean tsunami data indicated the tsunami would be non-damaging. Canceling this warning averted an evacuation in Hawaii, avoiding a loss in productivity valued at $68M.     

Regional Considerations of Coastline Change,Tsunami Damage and Recovery along the Southern Coast of the Bay of Izmit (The Kocaeli (Turkey) Earthquake of 17 August 1999)

Co-seismic phenomena along the south coastline included liquefaction, subsidenceand tsunami. Construction on areas composed of fluvial and alluvial sediments aswell as unconsolidated fill increased the risk by creating potential for amplificationof seismic waves. Cyclic mobility liquefaction was common along the coastline, andlevel-ground liquefaction was observed. Flow liquefaction is held forth as a possibilityin the Deirmendere submarine landslide. Damage to structures was markedly more in areas of unconsolidated sediments. One or more tsunami struck immediately after the event; the uniformity of tsunami impact indicating a wave coming from 310° suggests that submarine faulting was the major source of tsunami. Over 800,000 m² of subsidence resulted from sediment slumping, fault controlled subsidence, and possibly post-liquefaction sediment compaction. After a brief period of post-event abandonment, reclamation and use of coastal areas is well underway. This creates a tension between human desires pushing for quick and inexpensive re-inhabitation of the coastal areas, and the needs for zoning and building codes for risk reduction. In this high-risk area suchcontrary cultural mandates cannot yield ideal results. It is suggested that an alternativemodel of immediate post-event creation of parks and natural areas that would yield benefit is preferable in coastal areas rather than the enforcement approach currently favored.