Brief communication: Effective earthquake early warning systems: appropriate messaging and public awareness roles

The earthquake early warning systems (EEWSs) in China have achieved great progress, with warning alerts being successfully delivered to the public in some regions. We examined the performance of the EEWS in China's Sichuan Province during the 2019 Changning earthquake. Although its technical effectiveness was tested with the first alert released 10 s after the earthquake, we found that a big gap existed between the EEWS's message and the public's response. We highlight the importance of EEWS alert effectiveness and public participation for long-term resiliency, such as delivering useful alert messages through appropriate communication channels and training people to understand and properly respond.

Evidence-based guidelines for protective actions and earthquake early warning systems

Earthquake early warning systems (EEW) are becoming increasingly available or in development throughout the world. With public alerting in Mexico, Japan, Taiwan, and parts of the United States, it is important to provide evidence-based recommendations for protective action so people can protect themselves when they receive an alert. Best-practice warning communication research suggests that providing a protective action will increase the efficacy of the message. However, given the diversity of earthquakes and building types, as well as social and cultural contexts where these systems exist, the question is: what is the best protective action to recommend? The answer lies in maximizing life-saving protective actions during an earthquake event requires both contextually relevant messaging and widespread public education about appropriate protective actions under a range of conditions. By researching previous earthquake injury literature, examining current best practices and public education campaigns, key protective actions may be determined and used to increase the life-saving potential of earthquake early warning systems.

“Shaking in 5 Seconds!”—Performance and User Appreciation Assessment of the Earthquake Network Smartphone-Based Public Earthquake Early Warning System

Public earthquake early warning systems have the potential to reduce individual risk by warning people of approaching tremors, but their development has been hampered by costly infrastructure. Furthermore, both users’ understanding of such a service and their reactions to actual warnings have been the topic of only a few surveys. The smartphone app of the Earthquake Network initiative utilizes users’ smartphones as motion detectors and provides the first example of a purely smartphone-based earthquake early warning system, without the need for dedicated seismic station infrastructure and operating in multiple countries. We demonstrate that this system has issued early warnings in multiple countries, including for damaging shaking levels, and hence that this offers an alternative to conventional early warning systems in the foreseeable future. We also show that although warnings are understood and appreciated by users, notably to get psychologically prepared, only a fraction take protective actions such as “drop, cover, and hold.”

P-wave picking for earthquake early warning: Refinement of a T pd method

Summary Detecting P-wave onsets for on-line processing is an important component for real-time seismology. As earthquake early warning systems around the world come into operation, the importance of reliable P-wave detection has increased, since the accuracy of the earthquake information depends primarily on the quality of the detection. In addition to the accuracy of arrival time determination, the robustness in the presence of noise and the speed of detection are important factors in the methods used for the earthquake early warning. In this paper, we tried to improve the P-wave detection method designed for real-time processing of continuous waveforms. We used the new Tpd method, and proposed a refinement algorithm to determine the P-wave arrival time. Applying the refinement process substantially decreases the errors of the P-wave arrival time. Using 606 strong motion records of the 2011 Tohoku earthquake sequence to test the refinement methods, the median of the error was decreased from 0.15 s to 0.04 s. Only three P-wave arrivals were missed by the best threshold. Our results show that the Tpd method provides better accuracy for estimating the P-wave arrival time compared to the STA/LTA method. The Tpd method also shows better performance in detecting the P-wave arrivals of the target earthquakes in the presence of noise and coda of previous earthquakes. The Tpd method can be computed quickly so it would be suitable for the implementation in earthquake early warning systems.

Seismic Phase Association Based on the Maximum Likelihood Method

Phase association is a process that links seismic phases triggered at the stations of a seismic network to declare the occurrence of earthquakes. During phase association, a set of phases from different stations is examined to determine the common origin of phases within a specific region, predominantly on the basis of a grid search and the sum of observations. The association of seismic phases in local earthquake monitoring systems or earthquake early warning systems is often disturbed not only by transient noises, but also by large regional or teleseismic events. To mitigate this disturbance, we developed a seismic phase association method, binder_max, which uses the maximum likelihood method to associate seismic phases. The method is based on the framework of binder_ew, the phase associator of Earthworm, but it uses a likelihood distribution of the arrival information instead of stacking arrival information. Applying binder_max to data from seismic networks of South Korea and Ohio, United States, we found a significant improvement in the robustness of the method against large regional or teleseismic events compared to binder_ew. Our results indicate that binder_max can associate seismic phases of local earthquakes to the same degree as binder_ew as well as can avoid many of the false associations that have limited binder_ew.

Off-Network Earthquake Location by Earthquake Early Warning Systems: Methodology and Validation

ABSTRACT Regional source-based earthquake early warning systems perform three consecutive tasks: (1) detection and epicenter location, (2) magnitude determination, and (3) ground-motion prediction. The correctness of the magnitude determination is contingent on that of the epicenter location, and the credibility of the ground-motion prediction depends on those of the epicenter location and the magnitude determination. Thus, robust epicenter location scheme is key for regional earthquake early warning systems. Available source-based systems yield acceptably accurate locations when the earthquakes occur inside the real-time seismic network, but they return erroneous results otherwise. In this study, a real-time algorithm that is intended as a supplement to an existing regional earthquake early warning systems is introduced with the sole objective of ameliorating its off-network location capacity. The new algorithm combines measurements from three or more network stations that are analyzed jointly using an array methodology to give the P-wave slowness vector and S-phase arrival time. Prior to the S-phase picking, the nonarrival of the S phase is used for determining a minimum epicentral distance. This estimate is updated repeatedly with elapsed time until the S phase is picked. Thus, the system timeliness is not compromised by waiting for the S-phase arrival. After the S wave is picked, an epicentral location can be determined using a single array by intersecting the back-azimuth beam with the S-minus-P annulus. When several arrays are assembled, the back azimuth and P and S picks from all arrays are combined to constrain the epicenter. The performance of the array processing for back azimuth and S-wave picking is assessed using a large number of accelerograms, recorded by nine strong motion sensors of the KiK-net seismic network in Japan. The nine stations are treated as three distinct seismic arrays, comprising three stations each. Good agreement is found between array-based and catalog-reported parameters. Finally, the advantage of the new array methodology with respect to alternative schemes for back azimuth and distance is demonstrated.

Earthquake Early Warning (EEW) System: System Architecture, Data Modelling, and User Interface Design

Earthquake Early Warning Systems (EEWSs) development is essential to provide service to stakeholders and the public. The service is the information access regarding the information on the earthquake source area and its impact on the surrounding environment. This study aims to conduct a systematic literature review of peer-published studies focusing on the development of earthquake Early Warning Systems (EEWSs). The method of systematic review is well-established in research by Kitchenham et al. (2005). It is used to analyze the literature and answer defined research questions systematically. We found 16 papers related to system architecture, data modelling and user interface design of Earthquake Early Warning Systems (EEWSs) published in 2009-2020. Research that discusses data modelling is 6%, the user interface design is 38%, and system architecture is 56%. Overall, our findings show that the system architecture, data modelling and user interface of the development of Earthquake Early Warning Systems (EEWSs) in several countries have significant similarities. It can be modelled as a framework for the development of Earthquake Early Warning Systems (EEWSs).

Brief communication: Appropriate messaging is critical for effective earthquake early warning systems

The earthquake early warning systems (EEWSs) in China have achieved great progress, with warning alerts being successfully delivered to the public in some regions. We examined the performance of the EEWS in China's Sichuan Province during the 2019 Changning Earthquake. Although its technical effectiveness was tested with the first alert released 10 s after the earthquake, we found that a big gap existed between the EEWS's message and the public's response. We highlight the importance of EEWS alert effectiveness and public participation for long-term resiliency, such as delivering useful alert messages through appropriate communication channels and training people to understand and properly respond.

Earthquake Early Warning Systems as an Asset Risk Management Tool

Losses due to strong seismic events can amount to millions or billions of US dollars and can affect regions for large periods of time, even severely undermining the economy. Earthquake early warning systems have proven to be helpful tools to mitigate the social and economic impact on communities and businesses. Recent case studies are briefly described, followed by examples of proactive measures for assets, infrastructure, citizens education and empowerment, complementary to earthquake early warning systems.