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Seismology section

Seismology uses seismic waves to locate their origin, analyze the source properties or the structure of the Earth. The word "seismology" is of greek origin and means study of Earthquakes.


Seismic waves can be furthermore excited through mass displacement in oceans, volcanoes or glaciers or fluid flows in general. Seismic events are also induced by activities related to mining and geothermal energy.


To study the Earth's outermost shell, the crust, mining relevant deposits or the shallow subsurface, seismic waves can be excited artificially through vibrations or explosions. On a smaller scale, hammer blows or ultrasonic sources excite seismic waves to analyze material properties on the meter to centimeter-scale.


As seismic waves hold information on both their origin (the source) and the medium through which they propagate, they can be used to monitor natural or induced earthquake activity, to study source mechanisms or to image the interior of the Earth (seismic tomography).




Research Topics in SEISMOLOGY:

1. Seismic Tomography 
Inversion of longperiod seismic waveforms allows to derive threedimensional models of shear wave velocities of the lithosphere and upper mantle. Calculation of anisotropic models, automatized handling of large datasets, relation between deformation of the lithosphere and anisotropy are current topics of methodical research. Besides the waveforms themselves, certain parameters of the waveforms, such as traveltimes, polarisation of body waves, group- and phasevelocities of surface waves can be measured and applied in an inversion. Of particular interest is the study of the Earth's upper mantle beneath Europe, the Mediterranean and in Northern Europe around the Trans-European Suture Zone.

2. Ultrasonic studies
Analysis of seismic waves in the ultrasonic frequency band utilizes commonly the traveltimes of first arriving body waves. Using the entire waveform poses intriguing challenges. Using surface waves, one can study the upper few centimeters of a sample (e.g. rock, concrete) and determine variations in the elastic moduli which are indicative of, for example, weathering.

3. Seismicity studies
Characterizing the current state of active faults is an important topic of geophysical studies. Locating seismic events, analysis of their spatio-temporal clustering and studies of seismic coupling on the fault interface shed insight on the physical properties of active faults. Our particular focus is on studies of seismicity in the Aegean, one of the seismically most active regions in Europe.