- © 2009 by the Seismological Society of America
The term “earthquake early warning” (EEW) is used to describe real-time earthquake information systems that have the potential to provide warning prior to significant ground shaking. This is possible by rapidly detecting the energy radiating from an earthquake rupture and estimating the resulting ground shaking that will occur later in time either at the same location or some other location. Warning times range from a few seconds to a little more than a minute and are primarily a function of the distance of the user from the earthquake epicenter.
The concept has been around for as long as we have had electric communications (e.g., Cooper 1868), but it is only in the last two decades that the necessary instrumentation and methodologies have been developed (e.g., Nakamura 1988; Espinosa-Aranda et al. 1995). The last five years in particular have seen a rapid acceleration in the development and implementation of EEW, fueled by a combination of seismic network expansion, methodological development, and awareness of the increasing threat posed by earthquakes paired with desire by the seismological community to reduce risk.
This special issue of Seismological Research Letters is intended to facilitate communication of EEW methodologies and experiences in implementation. It complements the special section of Geophysical Research Letters published in March 2009 (Allen, Gasparini, and Kamigaichi 2009). Together, these collections of papers describe the science, engineering, and societal considerations of the active warning systems in Mexico, Japan, Taiwan, Turkey, and Romania and detail the development and testing of methodologies in the Unites States, Europe, and Asia (Figure 1). This introductory paper summarizes this content to provide an overview of EEW status around the world. We provide a summary of the various early warning methodologies and then describe the active implementation of early warning including the current users, the successes, …