Modelling rotational motions in the scattered seismic wave field

Time frame: 2011 - 2014

Summary
With the availability of sensors for the measurement of rotational motion of the Earth’s surface new possibilities for seismological investigations emerge. The three rotational degrees of freedom represent independent information that can significantly improve our knowledge about the subsurface. In this project we analyze the rotational motion of the Earth’s surface in response to teleseismic P-wave arrivals and local earthquakes. Rotation around the vertical axis is linked to horizontally polarized S-energy. In the P-coda this component is thus especially sensitive to heterogeneity in the crust that converts P- to S- energy by scattering. We use energy transfer theory to model the scattering process in the crust and the energy propagation in the waveguide between the surface and the Moho in order to explain the gradual build up of horizontally polarized S-energy in the P-coda. A rotational sensor will be installed at a Sachsennetz station close to the Vogtland/NW Bohemia earthquake swarm area to record truly co-located six components of motion in the source area. These and array derived six component measurements of local and regional earthquakes will be inverted for information about the statistical properties of the inhomogeneity of the Earth’s crust. The horizontal propagation of these waves will allow us to draw conclusions about possible statistical anisotropy of heterogeneity in the crust.

Contact:
Dr. Christoph Sens-Schönfelder (GFZ Potsdam)
Peter Gaebler (GFZ Potsdam)

Principle Investigators
Dr. Christoph Sens-Schönfelder (GFZ Potsdam)

Collaborations
Dr. Ludovic Margerin(Observatoire Midi Pyrenees, Toulouse)