New seismic imaging methods in Europe using noise
The extensive broadband station coverage in Europe and the challenging 3D structure makes the region ideal for developing imaging methods. We first show how seismic noise in Europe changes over space and time, with contributions from distinct source areas interacting differently depending on the station location, the season and the individual day. Some new methods are robust faced with these variations, as shown by imaging of anisotropic parameters and attenuation. Other methods perform poorly when daily noise correlations are stacked using all available data. For example, body wave reflections from the mantle transition zone (reflections on the 410 km and 660 km discontinuities) beneath the greater Alpine area can be enhanced by choosing to stack data for days with optimal noise conditions, rather than using several years of data. Future directions in seismic noise imaging and monitoring should include choices based on the noise characteristics, optimally setting the cursor between uniformly distributed and localised sources.