From Pinatubo to Hector Mine: how to use the atmosphere as a seismic sensor.

Acoustic coupling between solid Earth and its atmosphere has been observed since the 60s on either ground-based or satellite measurements. This coupling leads to clearly identified signals on seismic data after atmospheric events or on atmospheric or ionospheric measurementsafter big quakes. We developped a theory to adapt seismological methods to a global system including solid Earth and its atmosphere. It is therefore possible, with an extended basis of normal modes, to perform seismological analysis of such signals. Two examples are presented here: Pinatubo eruption and Hector Mine earthquake. The first case concerns an atmospheric source and seismic data: we performed an inversion of the source for a generalized source mechanism. We present results showing a reasonable source mechanism, considering the eruption history and energy release. The second case is for a seismic source and ionospheric data: firstly we present synthetics for different observables in the atmosphere and ionosphere, as a validation of our theory, secondly we use GPS Southern California network as new tool to image plasma perturbations in the ionosphere above the epicenter. We finally show different perspectives opened by this new field of investigation, both for seismology and for atmospheric sciences.