When analyzing the rupture of a large earthquake, geodetic data are often critical. These data are generally characterized by either a good temporal or a good spatial resolution, but rarely both. As a consequence, many studies analyze the coseismic rupture with data that also include one or more days of early postseismic deformation. Here, we invert simultaneously for the coseismic and postseismic slip with the condition that the sum of the two models remains compatible with data covering the two slip episodes. We validate the benefits of this approach with a toy model and an application to the 2009 M w 6.3 L'Aquila earthquake, using a Bayesian approach and accounting for epistemic uncertainties. For the L'Aquila earthquake, we find that if early postseismic deformation is not an explicitly acknowledged coseismic signal, coseismic slip models may overestimate the peak amplitude while long-term postseismic models may largely underestimate the total postseismic slip amplitude. This example illustrates how the proposed approach could improve our comprehension of the seismic cycle, fault frictional properties, and the spatial and temporal relationship between seismic rupture, afterslip, and aftershocks.

In December 2018, the National Aeronautics and Space Administration (NASA) Interior exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission deployed a seismometer on the surface of Mars. In preparation for the data analysis, in July 2017, the marsquake service initiated a blind test in which participants were asked to detect and characterize seismicity embedded in a one Earth year long synthetic data set of continuous waveforms. Synthetic data were computed for a single station, mimicking the streams that will be available from InSight as well as the expected tectonic and impact seismicity, and noise conditions on Mars (Clinton et al., 2017). In total, 84 teams from 20 countries registered for the blind test and 11 of them submitted their results in early 2018. The collection of documentations, methods, ideas, and codes submitted by the participants exceeds 100 pages. The teams proposed well established as well as novel methods to tackle the challenging target of building a global seismicity catalog using a single station. This article summarizes the performance of the teams and highlights the most successful contributions.

International audienceThe validity and the stability of a ground-motion simulation method based on the recordings of a single small event as an empirical Green's function (EGF) is tested on a seismic crisis that occurred 25 km offshore of the Guadeloupe Islands (Caribbean arc). We aim to determine if (1) the method enables us to reproduce the observed ground motion, (2) the choice of the small event taken as an EGF is crucial for the simulations, and (3) the method provides valuable results compared with ground-motion prediction equations (GMPEs). We have successively used the recordings of 10 small earthquakes (Mw 4.2–5.1) to simulate the ground motions generated by the mainshock (Mw 6.4), at 12 accelerometric stations. We first determined the moment and focal mechanisms of the 10 events chosen as an EGF, as well as the stress-drop ratio C between each of these events and the mainshock. Then, we simulated 500 accelerograms for each EGF and each station. A good reproduction of the mainshock response spectra, the peak ground acceleration, and the duration of the signal was obtained using 9 out of 10 EGFs. For stations with site effects, the results obtained are much closer to the real data than values given by the GMPEs on sediment sites. In the case of blind predictive simulation, we propose to calibrate the stress-drop ratio C through a comparison between the simulated response spectra on rock site stations and the values predicted by GMPEs