Inversion of meteor impact sources and analysis of the surface and shock waves generated by them
Séminaires Planétologie et Sciences Spatiales
Salle 727 - Lamarck A -
The interest for meteor impacts in planetary seismology has increased recently since to the progress on remote sensing. Orbiters, and other tracking or optical observations allow to accurately determine impact locations and, in some cases, their occurrence times. The importance of meteors as seismic sources is even greater in the case SEIS (Seismic Experiment of Interior Structure) of the future mission “InSight”, that is the only seismic mission planned for Mars so far and that will consists of only one seismometer. Constraint on the location gives meteors an edge over other seismic sources, reducing uncertainty on inversion for structure features and allowing to use differential time arrivals. In a first part of the talk, I will present an inversion technique for the calculation of the components of the moment tensor of the Chelyabinsk bolide that is based on a linear summation of the normal modes of the Earth. This source is equally modeled in atmospheric and lithospheric conditions of Mars. Meteor impacts generate body and surface seismic waves when they reach the surface of a planet. But when they explode into the atmosphere, due to ablation, they generate acoustic shock waves, which are converted into linear, seismic waves in the solid part and acoustic waves in the atmosphere. Modeling of these processes in order to predict the amplitude and waveform of the generated seismic signals require modeling of the atmospheric/ground coupling effects. In this context, different methodologies of modeling of the generated shock waves and extracting of their properties are also presented.