Evaluation of earthquake parameters used in the Indonesian Tsunami Early Warning System

Twenty-two of a total of 30 earthquake events reported by the Indonesian Agency for Geophysics, Climatology and Meteorology during the time period 2007–2010 were falsely issued as tsunamigenic by the Indonesian Tsunami Early Warning System (Ina-TEWS). These 30 earthquakes were of different magnitudes and occurred in different locations. This study aimed to evaluate the performance of the Ina-TEWS using common earthquake parameters, including the earthquake magnitude, origin time, depth, and epicenter. In total, 298 datasets assessed by the Ina-TEWS and the global centroid moment tensor (CMT) method were assessed. The global CMT method is considered by almost all seismologists to be a reference for the determination of these parameters as they have been proved to be accurate. It was found that the earthquake magnitude, origin time, and depth provided by the Ina-TEWS were significantly different from those given in the global CMT catalog, whereas the latitude and longitude positions of the events provided by both tsunami assessment systems were coincident. The performance of the Ina-TEWS, particularly in terms of accuracy, remains questionable and needs to be improved.     

W Phase Inversion and Tsunami Inundation Modeling for Tsunami Early Warning: Case Study for the 2011 Tohoku Event

Centroid moment tensor solutions for the 2011 Tohoku earthquake are determined by W phase inversions using 5 and 10 min data recorded by the Full Range Seismograph Network of Japan (F-net). By a scaling relation of moment magnitude to rupture area and an assumption of rigidity of 4 × 10¹⁰ N m^?2, simple rectangular earthquake fault models are estimated from the solutions. Tsunami inundations in the Sendai Plain, Minamisanriku, Rikuzentakata, and Taro are simulated using the estimated fault models. Then the simulated tsunami inundation area and heights are compared with the observations. Even the simulated tsunami heights and inundations from the W phase solution that used only 5 min data are considerably similar to the observations. The results are improved when using 10 min of W phase data. These show that the W phase solutions are reliable to be used for tsunami inundation modeling. Furthermore, the technique that combines W phase inversion and tsunami inundation modeling can produce results that have sufficient accuracy for tsunami early warning purposes.     

The 29 September 2009 Samoa Islands Tsunami: Simulations Based on the First Focal Mechanism Solutions and Implications on Tsunami Early Warning Strategies

The tsunamigenic earthquake (Mw?=?8.1) that occurred on 29 September 2009 at 17:48 UTC offshore of the Samoa archipelago east of the Tonga trench represents an example of the so-called ??outer-rise?? earthquakes. The areas most affected were the south coasts of Western and American Samoa, where almost 200 people were killed and run-up heights were measured in excess of 5?m at several locations along the coast. Moreover, tide gauge records showed a maximum peak-to-peak height of about 3.5?m near Pago Pago (American Samoa) and of 1.5?m offshore of Apia (Western Samoa). In this work, different fault models based on the focal mechanism solutions proposed by Global CMT and by USGS immediately after the 2009 Samoan earthquake are tested by comparing the near-field recorded signals (three offshore DART buoys and two coastal tide gauges) and the synthetic signals provided by the numerical simulations. The analysis points out that there are lights and shadows, in the sense that none of the computed tsunamis agrees satisfactorily with all the considered signals, although some of them reproduce some of the records quite well. This ??partial agreement?? and ??partial disagreement?? are analysed in the perspective of tsunami forecast and of Tsunami Early Warning System strategy.     

葡萄牙破坏性地震和海啸预警系统(DETWS)

本文介绍了葡萄牙破坏性地震和海啸预警系统(Destructive Earthquakes and Tsunami Warning System)的构成、地震与海啸信息的检测、海啸预警信息的发布。     

国际海啸预警系统(ITWS)

介绍了国际海啸预警系统的构成、地震与海啸信息的检测、海啸预警信息的发布，并介绍了太平洋海啸预警中心和阿拉斯加海啸预警中心。     

Long-Term Tsunami Data Archive Supports Tsunami Forecast, Warning, Research, and Mitigation

In response to the 2004 Indian Ocean tsunami, the United States began a careful review and strengthening of its programs aimed at reducing the consequences of tsunamis. Several reports and calls to action were drafted, including the Tsunami Warning and Education Act (Public Law 109–424) signed into law by the President in December 2006. NOAA’s National Geophysical Data Center (NGDC) and co-located World Data Center for Geophysics and Marine Geology (WDC-GMG) maintain a national and international tsunami data archive that fulfills part of the P.L. 109-424. The NGDC/WDC-GMG long-term tsunami data archive has expanded from the original global historical event databases and damage photo collection, to include tsunami deposits, coastal water-level data, DART? buoy data, and high-resolution coastal DEMs. These data are used to validate models, provide guidance to warning centers, develop tsunami hazard assessments, and educate the public about the risks from tsunamis. In this paper we discuss current steps and future actions to be taken by NGDC/WDC-GMG to support tsunami hazard mitigation research, to ultimately help save lives and improve the resiliency of coastal communities.     

Finite Fault Modeling in a Tsunami Warning Center Context

The US NOAA/NWS tsunami warning centers have relied on earthquake location and depth, and scalar measures of earthquake size and slowness to assess the potential for the generation of a destructive tsunami by an earthquake. Recent earthquakes, such as Peru 2001, Sumatra 2004 and the Java 2006, manifest some of the difficulties the warning centers face as they try to cope with unusual earthquakes. We have undertaken a study of a simple teleseismic waveform inverse model and applied it to the earthquakes of June 23, 2001 in Peru and of July 17, 2006 in Java. Synthetic numerical experiments suggest that the most salient features of the rupture history of an earthquake can be recovered. Furthermore the calculations can be conducted quickly enough to be useful in a warning center context. We have applied our technique to the Peru 2001 and recent Java 2006 earthquakes. Our overall results are consistent with those obtained from other studies. The results show why the Peru event initially looked slow to the US tsunami warning centers and that the Java event is a truly slow or tsunami earthquake. Clearly, the warning centers stand to benefit from an increased understanding of the earthquakes they monitor. Furthermore, better knowledge of the slip distribution along a fault will improve tsunami wave-height forecasts.     

香港海啸监测及警报系统的发展

地震监测、海啸数值模拟和海平面监测是监测和预报海啸的主要工具。为了有效监测南海北部可能发生的地震海啸,香港天文台（HKO）正在香港筹建一个宽频地震站,同时通过太平洋海啸警报及减灾系统（PTWS）的框架取得美国加州综合地震网（CISN）显示系统的实时地震信息,并通过世界气象组织（WM0）的全球通信系统（GTS）接收南海和西北太平洋的验潮站和海啸浮标数据以监测海面的波动情况。香港天文台通过联合国教科文组织（UNESCO）政府间海洋学委员会（IOC）取得海啸漫滩模式交换计划（TIME）下的海啸数值模式,把香港本地的高分辨率水深和地形数据融合在模式之内,并利用这个模式计算南海多处地区在不同地震情景下的海啸传播,为海啸预报提供重要的参考数据。     

Alaska Tsunami Warning Center's automatic and interactive computer processing system

The Alaska Tsunami Warning Center has the responsibility of providing timely tsunami warning services for Alaska and the west coasts of Canada and the United States. Recently, the ATWC implemented a new microcomputer system which is used for both automatic and interactive earthquake processing, and for disseminating critical information to the Tsunami Warning System recipients.Real-time seismic wave form data from 23 short-period and 9 long-period sites in Alaska, the lower 48 States, and Hawaii, are continually computer-monitored for the occurrence of an earthquake. Once detected from the short-period wave form data, pre- and post-earthquake data are displayed on a graphics terminal along with an indicator to identify the time of the onset of theP waves (P-picks). TheP-picks can easily be changed during or after data collection via a mouse. Magnitudes (M _b ,M _l ,M _B ,M _S ) are automatically computed from appropriate short- and long-period wave form data concurrently with the above processing. A second graphics terminal displays cycle-by-cycle long-period wave form data that was used to compute an earthquake'sM _B andM _S magnitudes.An earthquake's parametric data and other information are available and printed within tens of seconds after theP wave arrivals are recorded at the first 5 sites, then 7 sites, 9 sites, and a final parametric computation using all collected data. Three video display monitors are used for displaying the parameters, procedural aids, and a map showing the epicenter. Additionally, selected event parameters are immediately transmitted by VHF radio to alphanumeric beepers which are carried by standby duty personnel during those times that the Center is not manned.Using a dedicated video display terminal and printer, the interactive system can use data and parameters resulting from the automatic processes for concurrent parameter recomputations; perform additional computations; disseminate critical information; and generate procedural aids for duty geophysicists to facilitate an earthquake/tsunami investigation.     

Anatomy of Historical Tsunamis: Lessons Learned for Tsunami Warning

Tsunamis are high-impact disasters that can cause death and destruction locally within a few minutes of their occurrence and across oceans hours, even up to a day, afterward. Efforts to establish tsunami warning systems to protect life and property began in the Pacific after the 1946 Aleutian Islands tsunami caused casualties in Hawaii. Seismic and sea level data were used by a central control center to evaluate tsunamigenic potential and then issue alerts and warnings. The ensuing events of 1952, 1957, and 1960 tested the new system, which continued to expand and evolve from a United States system to an international system in 1965. The Tsunami Warning System in the Pacific (ITSU) steadily improved through the decades as more stations became available in real and near-real time through better communications technology and greater bandwidth. New analysis techniques, coupled with more data of higher quality, resulted in better detection, greater solution accuracy, and more reliable warnings, but limitations still exist in constraining the source and in accurately predicting propagation of the wave from source to shore. Tsunami event data collected over the last two decades through international tsunami science surveys have led to more realistic models for source generation and inundation, and within the warning centers, real-time tsunami wave forecasting will become a reality in the near future. The tsunami warning system is an international cooperative effort amongst countries supported by global and national monitoring networks and dedicated tsunami warning centers; the research community has contributed to the system by advancing and improving its analysis tools. Lessons learned from the earliest tsunamis provided the backbone for the present system, but despite 45 years of experience, the 2004 Indian Ocean tsunami reminded us that tsunamis strike and kill everywhere, not just in the Pacific. Today, a global intergovernmental tsunami warning system is coordinated under the United Nations. This paper reviews historical tsunamis, their warning activities, and their sea level records to highlight lessons learned with the focus on how these insights have helped to drive further development of tsunami warning systems and their tsunami warning centers. While the international systems do well for teletsunamis, faster detection, more accurate evaluations, and widespread timely alerts are still the goals, and challenges still remain to achieving early warning against the more frequent and destructive local tsunamis.     

基于数值预报技术的日本新一代海啸预警系统

日本是世界上地震海啸发生最频繁的国家之一。从1941年开始,日本气象厅就建立了自己的海啸预警系统。自1993年又一次遭受海啸灾害后,这些经历促使日本气象厅(JMA)开始研制基于数值预报技术的新一代海啸预警系统。该海啸预警系统包括地震监测网、基于数据库技术的快速数值预报以及基于卫星通讯的海啸预警产品快速分发系统这三部分。     

加州地震预警系统未来数年内建成

美国地球物理学联合会（AGU）于2009年12月14-15日在旧金山举行会议,根据会上提交的研究成果,未来几年内将建成加州地震预警系统。目前正在实施的该研究项目证实了建立加州地震预警系统的可行性,并展示了该系统建成后的布局。     

关于地震预警的几个问题

地震预警是建立在高密度地震台网基础上的新技术,本文就地震预警的一些基本概念、关键技术、预警效果、预警部署及其在防震减灾方面的作用等进行了讨论,指出了地震预警存在的问题,以及需要研究的方向,并首次提出了预警能力、预警无效区、预警受益区、预警反应时间的概念.地震预警能力受预警系统的制约,实际地震预警能力除与台网密度、预警模式、自动处理系统、数据传输模式、发布系统等因素有关外,还与地震破裂性质有关.同时强调地震预警部署是复杂的社会工程,需要全社会的共同参与.     

海南省南海地震监测和海啸预警服务

2004年底发生在印度洋的地震海啸造成的巨大灾难引起了人们广泛的关注。根据海南岛有仪器记录到地震海啸的事实,从构造角度讨论了海南岛未来遭受地震海啸袭击的可能性,强调了建立海南省南海地震监测和海啸预警系统的必要性和重要性,并提出了预警系统建设的初步设想。     

An Introductory Overview of Earthquake Early Warning

Earthquake early warning (EEW) is discriminated from earthquake prediction by using initial seismic waves to predict the severity of ground motion and issue the warning information to potential affected area. The warning information is useful to mitigate the disaster and decrease the losses of life and economy. We reviewed the development history of EEW worldwide and summarized the methodologies using in different systems. Some new sensors came and are coming into EEW giving more developing potential to future implementation. The success of earthquake disaster mitigation relies on the cooperation of the whole society.     

地震预警信息发布策略的探讨

地震预警是一种有效的减灾方式。面向公众的地震预警信息发布是一项复杂的系统工程,涉及发布主体、发布对象、发布内容和发布方式等多方面内容。本文通过分析国内外地震预警系统应用和信息发布策略,探讨提出了我国地震预警信息的发布主体的有效载体,与发布对象所对应的具体发布方式和发布内容等环节的操作方式,以期为政策制定提供一定的参考依据。