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Rapid estimation of the intensity of seismic ground motions is crucial for an effective rapid response when an earthquake occurs. To this end, maps of updated grond-motion fields (orshakemaps) are produced by using observations or measurements in near real-time to better constrain initial estimates. In this work, two types of observations are integrated to generate shakemaps right after an earthquake: the common type of data recorded by physicalsensors(seismic stations) and the data extracted from social sensors (Twitter), or the combination of both. We investigate an approach to extract an approximation of the macroseismic intensity from social sensors 10min after the earthquake; the approach relies on Twitter feeds to define the “felt area” where the earthquake was felt by the population, and the “unfelt locations” where the earthquake was not reported. Two recent earthquakes in France of moderate magnitude are studied and the results are compared to the official macroseismic intensity maps for validation. For the two studied cases, we note that Peak Ground Acceleration recordings far from theepicentertend to underestimate the entire macroseismic field, and that the tweets from “felt areas” are complementary for a better estimation of the intensity shakemap. We highlight the importance and the limits of each type of observations when generating the seismic shakemaps.

Systems for Rapid Response to Earthquakes (RRE) aim at providing reliable and near-real time ground-motion and loss estimates following an earthquake, in order to help authorities taking appropriate actions when needed. The purpose of this study is to review the state-of-the-art for RRE systems, focusing first on the tools and methods that have been developed for shake-map computation (i.e., taking into account the seismic recordings as well as macroseismic observations when available), in order to provide a map of the ground shaking intensity rapidly after an earthquake event. The second part focuses on the different approaches taken for rapid loss assessment, the ones based on shake-maps and the others. We give an overview of the current operating systems with emphasis on European ones, and we highlight their differences and identify the current gaps and pending issues. Finally, we call attention for the need to treat carefully uncertainties propagated at each calculation step, which added up are non-negligible, and are an important part of the result itself. Considering the full statistical distribution of loss and damage estimates provides more information than average or median values, and such statistics should therefore be provided by RRE systems and taken into account by decision-makers in order to take informed actions following an earthquake.

During their postseismic interventions, Urban Search and Rescue (USAR) teams are particularly exposed to the risk of collapse of buildings due to aftershocks. Risk reduction requires the capacity building of rescuers to anticipate incoming ground motions and to quickly protect themselves, which makes the concept of earthquake early warning (EEW) particularly interesting. In parallel to the recent scientific advances in EEW, it is crucial to understand what are the real expectations and needs of USAR teams in terms of protection against this risk, and to what extent EEW solutions could meet them. In this study, we conduct a survey to collect insights from 104 USAR rescuers (32 teams represented from 11 countries). Results highlight that aftershocks are a major concern for rescuers, and that the current tools and procedures do not allow an effective protection. In this context, we find that the concept of EEW is very favorably received by the respondents, who consider different types of possible actions upon receipt of an early warning. Depending on the time available, the perceive benefits range from simply reducing the surprise effect to moving teams into safe areas and stopping dangerous operations. Combined with the opportunities offered by the miniaturization of seismic monitoring means and by the high level of interoperability of USAR teams on an international scale, this study also provides a basis for the functional specifications of future solutions of EEW useful to all USAR teams, as well as for the definition of their modalities of engagement on the field.