Operational earthquake forecasting in Europe: progress,despite challenges

Is Europe-wide operational earthquake forecasting (OEF) possible? We discuss the myriad problems that prevent it today, many of which relate to heterogeneities in earthquake recording, processing, and reporting. We contemplate the difficulty of building models that cross political boundaries, and we consider the prospect of European OEF in light of recent efforts to harmonize long-term seismic hazard assessment among several nations. Emphasizing the Strategies and Tools for Real-time Earthquake Risk Reduction (REAKT) project, we report achievements related to short-term seismicity forecasting in Iceland and Italy that could apply elsewhere in Europe. In Iceland, collaboration fostered by REAKT resulted in a revised earthquake catalog and a prototype OEF system. We report results from an experiment conducted with this prototype; these results suggest ensemble models provide an information gain, updating models more frequently improves their forecast skill, and that OEF is computationally feasible. In Italy, REAKT supported the creation of an ensemble model that now issues weekly hazard forecasts. We present examples of these forecasts, highlighting the problem that OEF often yields low probabilities, which are difficult to interpret and convert into actionable decisions. Motivated by such low hazard probabilities, we highlight Europe’s pioneering efforts in operational earthquake loss forecasting and mention solutions to problems that currently prevent OEF at the European scale.     

Towards earthquake early warning for the Rion-Antirion bridge,Greece

Patras is the third largest city in Greece and an ideal candidate for earthquake early warning (EEW) applications due to its high seismic hazard, its existing research infrastructure and the presence of critical structures such as the Rion-Antirion bridge. Patras is located a few hundred kilometres from the Hellenic Arc, where very strong and potentially damaging earthquakes occur. This distance is large enough to allow a few tens of seconds of warning time prior to significant shaking, provided earthquakes are timely detected by a dense seismic network. Within the framework of the EC-funded project REAKT, the Virtual Seismologist (VS) EEW software was installed at Patras Seismological Laboratory. Its initial performance evaluation is presented here. In general VS provides magnitudes similar to the official, manually revised ones. Given the current station density and network telemetry, the average time that VS needs to deliver the first magnitude estimate is rather large, of the order of tens of seconds and not yet satisfactory for routine operational use of EEW. Even so, the system is able to provide up to 10 s of warning time prior to S-wave arrivals for events occurring on the Hellenic Arc. Our results indicate that the seismic networks in Greece need enhancements for regional EEW, either by adding stations or by upgrading the hardware to reduce delays. The application of an EEW system in the area is promising and, once operational, capable of mitigating earthquake risk.     

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.     

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.     

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...     

Earthquake early warning scenarios at critical facilities in the Eastern Caribbean

A feasibility study of an earthquake early warning (EEW) system was conducted for the Eastern Caribbean region using scenario earthquakes, corresponding to the maximum credible earthquakes and to the earthquakes associated with a return period of 475 years. Broadband synthetic seismograms were produced at selected critical facilities, where there is potential interest in the installation of an EEW system. The expected damage was derived from the synthetic seismograms and compared with the lead-time determined for both a regional and on-site EEW configuration. Next, the Virtual Seismologist EEW algorithm, as included in SeisComP3, was tested. Additional broadband synthetic seismograms were produced for the stations in the Eastern Caribbean seismic networks in order to simulate the real time behaviour of the seismic networks during the occurrence of the synthetic earthquakes and to assess the predictive capacity of the selected ground motion prediction equation. Expected peak ground parameters and lead-times at the critical facilities constitute the major outcome of the study.     

On-site structure-specific real-time risk assessment: perspectives from the REAKT project

The availability of computationally powerful and energy-efficient wireless sensing units or WSUs (one or more arranged in the form of a network in the vicinity and/or within a structure of interest) has led to new developments in the field of building and seismic strong motion monitoring. These WSUs can serve several functions. Those of largest earthquake engineering and engineering seismology interest are the recording of ground shaking the building is subjected to, as well as its response, and the capability of running rapid seismic risk analyses on the basis of vulnerability models of the structure, possibly coupled with recorded data. The REAKT project has shed light on a number of prospective applications of the last generation of monitoring devices for seismic risk management of critical structures. These applications refer to real-time and near-real-time risk assessment, that is: earthquake early warning, immediate post-event response evaluations based on recorded shaking, and short-term aftershock risk management for automated building tagging. This paper summarizes these perspectives that, despite still presenting some challenges that may limit readiness to date, have potential for scientific innovation in the field.     

Performance-based earthquake early warning

Significant investments are undergoing internationally to develop earthquake early warning (EEW) systems. So far, reasonably, the most of the research in this field was lead by seismologists as the issues to determine essential feasibility of EEW were mainly related to the earthquake source. Many of them have been brilliantly solved, and the principles of this discipline are collected in the so-called real-time seismology. On the other hand, operating EEW systems rely on general-purpose intensity measures as proxies for the impending ground motion potential and are suitable for population alert. In fact, to date, comparatively little attention was given to EEW by earthquake engineering, and design approaches for structure-specific EEW are mostly lacking. Applications to site-specific systems have not been extensively investigated and EEW convenience is not yet proven except a few pioneering cases, although the topic is certainly worthwhile. For example, in structure-specific EEW the determination of appropriate alarm thresholds is important when the false alarm may induce significant losses; similarly, economic appeal with respect to other risk mitigation strategies as seismic upgrade should be assessed. In the paper the least issues to be faced in the design of engineering applications of EEW are reviewed and some work done in this direction is discussed. The review presented intends to summarize the work of the author and co-workers in this field illustrating a possible performance-based approach for the design of structure-specific applications of EEW.     

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 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).     

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.     

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.     

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.     

地震预警震级确定方法研究

地震预警技术是减轻地震灾害损失的有效手段之一．地震预警系统中,地震震级计算是最重要也是最困难的部分之一．利用日本KiK-net台网和四川汶川余震共142次地震事件的记录,分别采用tau;c和Pd方法统计得到了地震预警震级的计算公式,震级计算的方差分别为0.62和0.56个震级单位．为消除震级计算过程中出现的震级饱和现象,作者拓展了Pd方法,提出了一套对位移幅值连续追踪测定的算法．当时间窗长度为10 s时,采用该方法的震级计算方差仅为0.37个震级单位,充分满足地震预警系统的需求．同时,该方法也实现了信息的连续过渡,提高了对现有信息的利用率．最后,还对位移幅值Pd用于地震动峰值PGV的估计以及不同特征参数间的相容性等内容进行了讨论．      

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.     

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.     

烈度仪用于地震预警的可靠性研究——以高雄MS6.8地震为例

以2016年2月6日我国台湾高雄M_S6.8地震中烈度仪观测网的实际记录为研究对象,通过对烈度仪台站的震相捡拾结果精度、峰值地震动衰减关系适用性、预警震级计算结果准确性等3方面的对比分析,研究了烈度仪用于地震预警时的优势和可靠性,并讨论了可能存在的问题和风险.研究结果表明:对于震中附近具有较高信噪比的烈度仪台站,采用现有震相捡拾方法即可获得较准确的震相到时信息;现有的地震动衰减关系并不完全适用于烈度仪台网,直接应用这些关系式时存在一定风险;基于密集布设的烈度仪观测台网,在较短时间即可获取大量信息,采用已有预警震级估算方法的计算结果有较高的准确性.      

利用P波参数阈值实时估算地震预警潜在破坏区范围

由于传统的潜在破坏区范围估算方法只能在已获取到震中位置和地震事件结束后才能产出,且往往需要数分钟的耗时,其实时性已无法满足地震预警要求。因此,为了快速产出潜在破坏区范围估算结果并将其用于预警,本文采用了一种结合现地预警技术和区域预警技术、基于预警参数（位移幅值P_d和特征周期τ_c）阈值的实时潜在破坏区范围估算方法。首先利用国内地震事件（4.0≤M_S≤8.0）的记录数据和日本强震动观测事件（6.5≤M_J≤8.0）的数据拟合出特定的适应于我国的参数关系式,包括τ_c与震级M的相关性、P_d与峰值速度PGV的相关性以及P_d与τ_c和震源距R的相关性;其次,根据最小震级（M_S6.0）和仪器烈度（Ⅶ度）定义相应的参数阈值（P_d＝0.1 cm和τ_c＝1.1 s）;最后,利用已有的3次破坏性地震事件数据开展线下模拟,对该方法的适应性和时效性进行了验证。结果表明,对于2013年M_S7.0四川芦山和2014年M_S6.5云南鲁甸两次中强地震,震后约10 s即可获取到比较稳定的潜在破坏区范围估计结果;而对于2008年M_S8.0汶川特大地震,在其记录台站分布密度不高的情况下,震后40 s左右的估算结果始呈稳定状态。      

Operational earthquake loss forecasting: a retrospective analysis of some recent Italian seismic sequences

Operational earthquake forecasting (OEF) relies on real-time monitoring of seismic activity in an area of interest to provide constant (e.g., daily) updates of the expected number of events exceeding a certain magnitude threshold in a given time window (e.g., 1 week). It has been demonstrated that the rates from OEF can be used to estimate expected values of the seismic losses in the same time interval OEF refers to. This is a procedure recently defined as operational earthquake loss forecasting (OELF), which may be the basis for rational short-term seismic risk assessment and management. In Italy, an experimental OELF system, named MANTIS-K, is currently under testing. It is based on weekly rates of earthquakes exceeding magnitude (M) 4, which are updated once a day or right after the occurrence in the country of an M 3.5+ earthquake. It also relies on large-scale structural vulnerability and exposure data, which serve to the system to provide continuously the weekly expected number of: (1) collapsed buildings, (2) displaced residents, and (3) casualties. While the probabilistic basis of MANTIS-K was described in previous work, in this study OELF is critically discussed with respect to three recent Italian seismic sequences. The aim is threefold: (1) illustrating all the features of the OELF system in place; (2) providing insights to evaluate whether if it would have been a useful additional tool for short-term management; (3) recognizing common features, if any, among the losses computed for different sequences.     

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.