Expected loss‐based alarm threshold set for earthquake early warning systems

Earthquake early warning systems (EEWS) seem to have potential as tools for real‐time seismic risk management and mitigation. In fact, although the evacuation of buildings requires warning time not available in many urbanized areas threatened by seismic hazard, they may still be used for the real‐time protection of critical facilities using automatic systems in order to reduce the losses subsequent to a catastrophic event. This is possible due to the real‐time seismology, which consists of methods and procedures for the rapid estimation of earthquake features, as magnitude and location, based on measurements made on the first seconds of the P‐waves. An earthquake engineering application of earthquake early warning (EEW) may be intended as a system able to issue the alarm, if some recorded parameter exceeds a given threshold, to activate risk mitigation actions before the quake strikes at a site of interest. Feasibility analysis and design of such EEWS require the assessment of the expected loss reduction due to the security action and set of the alarm threshold. In this paper a procedure to carry out these tasks in the performance‐based earthquake engineering probabilistic framework is proposed. A merely illustrative example refers to a simple structure assumed to be a classroom. Structural damage and non‐structural collapses are considered; the security action is to shelter occupants below the desks. The cost due to a false alarm is assumed to be related to the interruption of didactic activities. Results show how the comparison of the expected losses, for the alarm‐issuance and non‐issuance cases, allows setting the alarm threshold on a quantitative and consistent basis, and how it may be a tool for the design of engineering applications of EEW. Copyright © 2007 John Wiley & Sons, Ltd.     

On an earthquake early warning system (EEW) and its applications

It is clear that the basic countermeasure against earthquake strong motion is to reinforce buildings and other structures. Realtime earthquake disaster prevention is a countermeasure during the earthquake itself and is different from realtime seismology. An EEW, earthquake early warning system, is required to trigger realtime earthquake disaster prevention. It is important to avoid too much trust in EEW for the disaster prevention. This paper describes the concept of an EEW and gives a brief history, which eventually led to the development of the UrEDAS, the urgent earthquake detection and alarm system, the first operational P-wave early warning system. A real-world example of disaster prevention by this system is described. Finally, the role of national or public organizations in earthquake disaster prevention will be discussed, with special emphasis on the situation in Japan.     

地震预警定位方法研究

实时地震定位是地震预警系统中必须解决的关键问题之一.文中在借鉴已有实时地震定位方法的基础上并结合我国台网的实际情况,推导得到一套利用前三/四台P波、S波到时信息进行实时定位的算法.作者选取2000年至2008年问福建省地震监测台网记录到的68个3.0级以上地震对该算法进行验证.研究结果表明,采用文中方法的定位结果具有一...     

地震预警实质的探讨

随着国家地震烈度速报与预警工程的开展,“地震预警”越来越进入公众的视线,国内外关于“什么是地震预警”的问题越来越多,对地震预警技术的解释也多种多样。本文论述了我国地震预警的进展,地震预警的实质和局限性。地震预警实质是地震观测进入密集观测新阶段,地震速报从分钟级发展到秒级超快地震速报,也就是地震警报。由于在地震预警实际应用中受预警盲区和地震强度估算不准确的局限,地震科学家对地震预警技术应用效能的认识也在不断加深和变化,逐步认识了发挥地震预警的警报作用的重要性。同时,地震预警是复杂的社会工程,引导公众认识地震预警的局限性,才能有效发挥减灾效能。      

地震预警震级计算方法研究综述

地震预警系统是减轻地震灾害的有效手段之一,世界上多个国家和地区都已经建立了地震预警系统,并在实际应用中取得了显著的减灾实效.由于地震预警系统应用中的高度时效性要求,预警震级计算是整个地震预警系统中最重要也是最困难的一部分.本文回顾总结了地震预警研究中采用的一些震级计算方法,并将其归纳为三大类算法:与初始周期相关的算法、与初始幅值相关的算法和与初始强度相关的算法.对每种算法都做了详尽介绍和仔细分析,同时列举出与该算法相关的研究成果.通过对这些算法的分析总结并结合我国地震观测台网的实际情况,作者推荐τc、Pd两种方法作为我国地震预警系统建设中优先采用的两种预警震级算法.     

Earthquake early warning as a tool for improving society’s resilience and crisis response

Increasing vulnerability of metropolitan areas to earthquake and the very low probability level at which short term earthquake forecasting is possible make earthquake early warning methods (EEW) the main viable alternative for effective risk reduction in cities. Preventive actions, such as retrofitting and building and the diffusion of construction codes, are of course essential. They are not sufficient. A substantial proportion of the population in areas of higher earthquake hazard still reside in buildings that do not meet modern earthquake resistant standards, and cannot currently be strengthened in an economically viable manner. As demonstrated in Japan EEW has the potential of significantly contributing to reduce individual vulnerability of urban population to earthquakes. Future research on EEW should be focused on its implementation to protect lifelines, infrastructures and strategic buildings, and it should include training of administrators and people who can fully exploit the technological advantages offered by EEW systems. In particular it should foresee extensive cost-benefit analysis for each potential application, the identification and solution of legal problems (such as liability in the event of false or missed alarms), education and training, both for mitigation and response, as well as detection and processing within 1 s of the first seismic wave arrivals. Further objectives include the development of people-centred EEW, specialized IT and decision making support systems, integration of sensors, communications and decision making systems, integration into programs of eco-sustainable development, and integration with other EW systems (all hazard systems).     

Deep learning for P-wave arrival picking in earthquake early warning

Fast and accurate P-wave arrival picking significantly affects the performance of earthquake early warning(EEW)systems.Automated P-wave picking algorithms used in EEW have encountered problems of falsely picking up noise,missing P-waves and inaccurate P-wave arrival estimation.To address these issues,an automatic algorithm based on the convolution neural network(DPick)was developed,and trained with a moderate number of data sets of 17,717 accelerograms.Compared to the widely used approach of the short-term average/long-term average of signal characteristic function(STA/LTA),DPick is 1.6 times less likely to detect noise as a P-wave,and 76 times less likely to miss P-waves.In terms of estimating P-wave arrival time,when the detection task is completed within 1 s,DPick′s detection occurrence is 7.4 times that of STA/LTA in the 0.05 s error band,and 1.6 times when the error band is 0.10 s.This verified that the proposed method has the potential for wide applications in EEW.     

基于国产密码的地震预警服务系统防篡改框架设计与应用

地震预警服务系统是地震预警系统的重要组成部分,是网络安全的重点防护目标和对象。由于地震预警信息影响广泛,需要保证其真实性、完整性及服务的高时效性,为此设计一种基于国产密码算法的地震预警服务系统防篡改框架,使用数字证书和协同签名技术,对身份鉴别和消息完整性校验过程进行优化,使得密码算法的时间消耗足够小。设计完成后,上述操作消耗的时间小于0.2 s,兼顾了地震预警信息的安全性和高时效性。     

全球地震早期预警研究综述

近年来地震预警技术在国际上得到迅速的发展,并有成功预警且收到减灾实效的先例.本文系统介绍了地震早期预警的方法,包括波前探测、P波应用、现地预警和区域预警;介绍了地震早期预警系统在墨西哥、日本、土耳其、中国台湾和罗马尼亚等国家和地区的应用情况.还对地震预警中目前存在的问题和挑战以及远景进行了分析.     

State-of-the art and future of earthquake early warning in the European region

European researchers and seismic networks are active in developing new approaches to earthquake early warning (EEW), implementing and operating test EEW systems, and in some cases, offering operational EEW to end users. We present the key recent developments in EEW research in Europe, describe the networks and regions where EEW is currently in testing or development, and highlight the two systems in Turkey and Romania that currently provide operational systems to a limited set of end users.     

Earthquake magnitude estimation using the τ c and P d method for earthquake early warning systems

Earthquake early warning (EEW) systems are one of the most effective ways to reduce earthquake disaster. Earthquake magnitude estimation is one of the most important and also the most difficult parts of the entire EEW system. In this paper, based on 142 earthquake events and 253 seismic records that were recorded by the KiK-net in Japan, and aftershocks of the large Wenchuan earthquake in Sichuan, we obtained earthquake magnitude estimation relationships using the τ _c and P _d methods. The standard variances of magnitude calculation of these two formulas are ±0.65 and ±0.56, respectively. The P _d value can also be used to estimate the peak ground motion of velocity, then warning information can be released to the public rapidly, according to the estimation results. In order to insure the stability and reliability of magnitude estimation results, we propose a compatibility test according to the natures of these two parameters. The reliability of the early warning information is significantly improved though this test.     

现今地震预警技术及其在国内发展状况的探讨

本文首先从地震预警的概念、系统构成和技术方法等方面入手,对目前国际上地震预警技术的最新研究进展和热点问题进行了全面的论述。继而通过对国内发展现状的系统分析,认为地震预警系统的开展在政府、社会、台网建设和研究基础等方面都已经具备了基本的条件。结合当前国内的实际情况,对地震预警系统在实施过程中可能遇到的技术问题和非技术性挑战进行了估计,并建议加强法律措施、公众教育、震害防御等方面的配套工作,最大限度地发挥地震预警系统在防震减灾工作中的作用。     

An integrated earthquake early warning system and its performance at schools in Taiwan

An earthquake early warning (EEW) system with integration of regional and onsite approaches was installed at nine demonstration stations in several districts of Taiwan for taking advantages of both approaches. The system performance was evaluated by a 3-year experiment at schools, which experienced five major earthquakes during this period. The blind zone of warning was effectively reduced by the integrated EEW system. The predicted intensities from EEW demonstration stations showed acceptable accuracy compared to field observations. The operation experience from an earthquake event proved that students could calmly carry out correct action before the seismic wave arrived using some warning time provided by the EEW system. Through successful operation in practice, the integrated EEW system was verified as an effective tool for disaster prevention at schools.     

基于支持向量机的2021年2月13日日本福岛近海Mj7.3级地震震级估算

2021年2月13日日本福岛县近海发生M_j7.3级地震,触发了日本气象厅地震预警系统,系统在首台触发后5.6s发出震级为M_j6.3级的预警第1报,首台触发后10s对公众发布警报、预警震级为M_j6.4级。基于多类型特征参数输入的机器学习支持向量机震级估算模型（SVM-M）,利用2021年2月13日日本福岛县近海M_j7.3级地震获取的日本K-net强震动观测数据,分析SVM-M模型在该次地震中首台触发初期（首台触发后1~10s）的震级估算效能。结果表明:SVM-M震级估算模型,在首台触发后1s即可给出M_j6.3级的震级估算结果,与日本气象厅在首台触发后5.6s发布的预警第1报震级相同;随着时间窗的增加,首台触发后5s和10s,SVM-M模型的震级估算结果分别是M_j6.7级和M_j6.6级,均大于日本气象厅首台触发后10s对公众发布警报的预警震级。该次地震的离线模拟结果表明:SVM-M模型可在地震发生初期有效提高地震预警震级确定的准确性和时效性。     

Prediction of response spectra via real-time earthquake measurements

The development and implementation of an earthquake early warning system (EEWS), both in regional or on-site configurations can help to mitigate the losses due to the occurrence of moderate-to-large earthquakes in densely populated and/or industrialized areas. The capability of an EEWS to provide real-time estimates of source parameters (location and magnitude) can be used to take some countermeasures during the earthquake occurrence and before the arriving of the most destructive waves at the site of interest. However, some critical issues are peculiar of EEWS and need further investigation: (1) the uncertainties on earthquake magnitude and location estimates based on the measurements of some observed quantities in the very early portion of the recorded signals; (2) the selection of the most appropriate parameter to be used to predict the ground motion amplitude both in near- and far-source ranges; (3) the use of the estimates provided by the EEWS for structural engineering and risk mitigation applications.In the present study, the issues above are discussed using the Campania–Lucania region (Southern Apennines) in Italy, as test-site area. In this region a prototype system for earthquake early warning, and more generally for seismic alert management, is under development. The system is based on a dense, wide dynamic accelerometric network deployed in the area where the moderate-to-large earthquake causative fault systems are located.The uncertainty analysis is performed through a real-time probabilistic seismic hazard analysis by using two different approaches. The first is the Bayesian approach that implicitly integrate both the time evolving estimate of earthquake parameters, the probability density functions and the variability of ground motion propagation providing the most complete information. The second is a classical point estimate approach which does not account for the probability density function of the magnitude and only uses the average of the estimates performed at each seismic station.Both the approaches are applied to two main towns located in the area of interest, Napoli and Avellino, for which a missed and false alarm analysis is presented by means of a scenario earthquake: an M 7.0 seismic event located at the centre of the seismic network.Concerning the ground motion prediction, attention is focused on the response spectra as the most appropriate function to characterize the ground motion for earthquake engineering applications of EEWS.     

A new prototype system for earthquake early warning in Taiwan

A new prototype earthquake early warning (EEW) system is being developed and tested using a real-time seismographic network currently in operation in Taiwan. This system is based on the Earthworm environment which carries out integrated analysis of real-time broadband, strong-motion and short-period signals. The peak amplitude of displacement in the three seconds after the P arrival, dubbed P_d, is used for the magnitude determination. Incoming signals are processed in real time. When a large earthquake occurs, P-wave arrival times and P_d will be estimated for location and magnitude determinations for EEW purpose. In a test of 54 felt earthquakes, this system can report earthquake information in 18.8±4.1 s after the earthquake occurrence with an average difference in epicenter locations of 6.3±5.7 km, and an average difference in depths of 7.9±6.6 km from catalogues. The magnitudes approach a 1:1 relationship to the reported magnitudes with a standard deviation of 0.51. Therefore, this system can provide early warning before the arrival of S-wave for metropolitan areas located 70 km away from the epicenter. This new system is still under development and being improved, with the hope of replacing the current operational EEW system in the future.     

Progress of the earthquake early warning system in Fujian, China

In this article, we systematically introduce the latest progress of the earthquake early warning (EEW) system in Fujian, China. We focus on the following key technologies and methods: continuous earthquake location and its error evaluation; magnitude estimation; reliability judgment of EEW system information; use of double-parameter principle in EEW system information release threshold; real-time estimation of seismic intensity and available time for target areas; seismic-monitoring network and data sharing platform; EEW system information release and receiving platform; software test platform; and test results statistical analysis. Based on strong ground motion data received in the mainshock of the Wenchuan earthquake, the EEW system developed by the above algorithm is simulated online, and the results show that the system can reduce earthquake hazards effectively. In addition, we analyzed four earthquake cases with magnitude greater than 5.5 processed by our EEW system since the online-testing that was started one year ago, and results indicate that our system can effectively reduce earthquake hazards and have high practical significance.     

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.     

Earthquake early warning: Concepts,methods and physical grounds

Modern technology allows real-time seismic monitoring facilities to evolve into earthquake early warning (EEW) systems, capable of reducing deaths, injuries, and economic losses, as well as of speeding up rescue response and damage recovery. The objective of an EEW system is to estimate in a fast and reliable way the earthquake’s damage potential, before the strong shaking hits a given target.     

Designing efficient earthquake early warning systems: case study of Almaty, Kazakhstan

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful implementation in other earthquake-prone areas. Such systems aim to provide short (seconds to tens of seconds) warnings of impending disaster, enabling the first risk mitigation and damage control steps to be taken. This study presents the feasibility of such a system for Almaty, Kazakhstan. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. Factors like the possibility of station failure, elevation and access difficulty to a potential site, and the potential usefulness of existing stations in the region are considered. We present a large set of possible efficient networks, to which further selection criteria can be applied by both the installation teams and the end user, such as authorities in Almaty.