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Early warnings and preparedness1 often need to go hand in hand. In the absence of preparedness, there is little guarantee that early warnings will serve a useful purpose; especially when there is a very short lead-in time between warnings and the applicable crisis event. This is particularly true for earthquake early warning (EEW) systems, which prompt alerted populations to take the protective actions required to avoid major injuries or death. For example, dropping, covering, and holding on is the protective action which is commonly recommended in the United States of America and in many other parts of the world. The rapid onset of major shaking following earthquake alerts places imperiled populations under severe timing and psychological pressure when attempting to take these actions. This is because EEW systems provide public alerts within seconds or a little over a minute before the onset of a major earthquake (Allen et al., 2009). Relevant protective actions must therefore be a type of response that has been well prepared in advance. Among other benefits discussed below, well-prepared responses will help avoid more instinctual but counterproductive alternatives such as running or freezing in place in response to EEW alerts.
EEW systems are designed to detect primary (P) earthquake shockwaves and use them to predict the arrival of more destructive secondary (S) shockwaves (Allen et al., 2018). Alerts can then be sent to potentially affected populations through siren networks, public announcement systems, cell tower broadcasts to individuals’ mobile phones (Allen et al., 2009, 2018; Espinosa-Aranda, 1995), and other alerting devices. This kind of approach to EEW has received major commitments from several governments around the world, leading to the development of systems in Mexico, Turkey, Romania, and in the United States of America (Strauss & Allen, 2016). Asian EEW capabilities include systems based in Japan, another in Taiwan (Strauss & Allen, 2016), and another on the Chinese mainland (Strauss & Allen, 2016; Li, Zhang & Tang, 2017).
Among these examples, Mexico established the world’s first EEW system in 1991 (Allen et al., 2009, 2018). Japan has had a national EEW system in place since 2007 (Allen et al., 2018: Fujinawa & Noda, 2013; Kamigaichi, 2009). Although the remainder of this paper discusses other national contexts, it will focus on these Mexican and Japanese systems – because they have been the most established, and heavily documented, EEW systems in the world. Both systems have steadily improved sensor and alert accuracy, along with the confidence that imperiled populations appear to place in the resulting alerts. However, as outlined further below, a number of distinctly psychological issues remain to be addressed.
The West Coast of the USA has a much newer EEW system, called ShakeAlert. As at 2019, this system was in a testing phase with pilot partners in the states of California, Oregon, and Washington (Chung et al., 2020). The United States had planned to implement the West Coast EEW system at an initial cost of 38 million USD, and with ongoing costs of 16.1 million USD in additional funding per year (Strauss & Allen, 2016). These costs represent a particularly substantial investment into seismological research and monitoring. However, the investment pales in comparison to direct economic losses of more than 210 billion USD (Kajitani et al., 2013) and over 87,000 (Han et al., 2013) lives lost in individual earthquake events occurring within the last 15 years.