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Lebanon is a densely populated country crossed by major faults. Historical seismicity shows the potential of earthquakes with magnitudes >7, but large earthquakes have never been instrumentally recorded in Lebanon. Here, we propose a method to simulate near-fault broadband ground motions for a potential Mw 7 earthquake on the Yammouneh fault (YF)--the largest branch of the Dead Sea Transform fault that bisects Lebanon from north to south. First, we performed the first 3D tomography study of Lebanon using ambient noise correlation, which showed that Lebanon could be approximated by a 1D velocity structure for low-frequency (LF) ground-motion simulation purposes. Second, we generated suites of kinematic rupture models on the YF, accounting for heterogeneity of the rupture process, and uncertainty of the rupture velocity and hypocenter location. The radiated seismic energy was next propagated in the inferred 1D velocity model to obtain suites of LF ground motions (<1 Hz) at four hypothetical near-fault seismic stations. These LF simulations included the main features of near-fault ground motions, such as the impulsive character of ground velocity due to the rupture directivity or fling-step effects (so-called pulse-like ground motions). Third, to obtain broadband ground motions (up to 10 Hz), we proposed a hybrid technique that combined the simulated LF ground motions with high-frequency (HF) stochastic simulations, which were empirically calibrated using a worldwide database of near-fault recordings. Contrary to other hybrid approaches, in which the LF and HF motions are generally computed independently, the characteristics of stochastic HF ground motions were conditioned on those of LF ground motions (namely on the characteristics of the velocity pulse, if it existed, or on the absence of a pulse). The simulated peak ground accelerations were in agreement with the ones reported in the Next Generation Attenuation-West2 (NGA-West2) database for similar magnitude and distances and with three NGA-West2 ground-motion prediction equations. [ABSTRACT FROM AUTHOR]

The ground velocity pulses generated by rupture directivity effects in the near-fault region can cause a large amount of damage to structures. Proper estimation of the period of such velocity pulses is of particular importance in characterizing near-fault seismic hazard and mitigating potential damage. We propose a simple equation to determine the pulse period as a function of the site location with respect to the fault rupture (defined by the hypocentral distance hypD, the closest distance to the rupture area clsD, and the length of the rupture area that breaks toward the site D) and some basic rupture properties (average rupture speed and average rise time). Our equation is first validated from a dataset of synthetic velocity time histories, deploying simulations of various strike-slip extended ruptures in a homogeneous medium. The analysis of the synthetic dataset confirms that the pulse period does not depend on the whole rupture area, but only on the parameter D. It also reveals that the pulse period is not sensitive to the level of slip heterogeneity on the fault plane. Our model is tested next on a real dataset build from the Next Generation Attenuation-West2 Project database, compiling 110 observations of velocity pulse periods from 10 strike-slip events and 6 non-strike-slip events. The standard deviation of the natural logarithm residuals between observations and predictions is ~0.5. Furthermore, the correlation coefficient between observations and predictions equals ~0.8, indicating that despite its simplicity, our model explains fairly well the spatial variability of the pulse periods. [ABSTRACT FROM AUTHOR]

Road network systems play a critical role in the emergency phase following an earthquake, since they constitute the main vector of transportation of rescue teams, first-aid responders or victims in need of evacuation. While several studies have focused on how to organize multi-agent travels via a traffic plan, the present work focuses on how to immediately help first-aid responders, at a moment when the actual damage state of the road network is still mostly unknown. Therefore, in such an uncertain context, a probabilistic framework is used in order to evaluate the failure probability of exposed road components and the accessibility probability between two locations of the network, via a decomposition into minimum link sets. Such data is then used to extract relevant indicators for each potential travel itinerary, such as the expected travel time (accounting for potential disruptions along the route and the need to use a back-up itinerary) or the reliability of the itinerary and its back-ups. Given predefined road user profiles, with different weightings of indicator preferences, the various travel options may be evaluated in a decision matrix in order to assist the choice of the most adequate itinerary. Finally, such as decision support system is demonstrated on a road network in the Pyrenees mountain range (France), where several travel options (i.e., fastest or safest routes from the damaged area to nearby hospitals, or from rescue centres to the damage area) are evaluated for a few earthquake scenarios and characteristic user profiles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (or shakemaps) 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 physical sensors (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 10 min 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 the epicenter tend 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. [ABSTRACT FROM AUTHOR]