Harm J Van AvendonkResearch Scientist, Institute for Geophysics
Harm Van Avendonk has engaged in marine and land-based seismic studies of the deep structure of the Earth's crust, particularly near the plate boundaries. Wide-angle seismic refraction data can provide good constraints on the geometry and composition of the deep crust. He uses imaging methods such as seismic tomography and wide-angle migration and waveform analysis to interpret seismic refraction data sets.
Marine seismic reflection and refraction profiles across rifted margins, such as those of Newfoundland, show us the style and the amount of crustal extension during continental rifting. Comparison of the seismic images with geodynamic modeling of continental extension suggests that uniform stretching and lithospheric detachment faulting together shape the structure of rifted margins. Harm's latest project in continental rifting is a new seismic refraction study of the opening of the Gulf of Mexico.
Active-source seismic studies of subduction zones show the structure and composition of the downgoing oceanic lithosphere and overlying arc crust. Bending of the downgoing plate leads to fratucturing of the crust, infiltration of seawater and serpentinization of the oceanic mantle. Seismic images of the downgoing Cocos plate offshore Nicaragua clearly show serpentinization of the upper mantle through lowering of the seismic wave speeds. Seismic refraction studies of island arcs show that the composition of island arcs is much more mafic than the average composition of continental crust. Differentiation and reworking of arc crust upon accretion to continents may explain why continental crust is much more felsic on average.
Areas of Expertise
Van Avendonk is an active-source seismologist who specializes in the acquisition and inversion of seismic refraction data on land and at sea. Often these seismic refraction data are used for a tomographic inversion. The resultant seismic velocity models help us to interpret the composition of the Earth’s crust and mantle, the geometry of sedimentary basins, and the structure of plate boundaries.
Dinstinguished Lecture Series, Lecturer, GeoPRISMS (2011 - 2011)
Extension of continental crust at the eastern Grand Banks, Newfoundland, University of Memphis, Memphis, TN. (2011)
The life cycle of rifted margins, Pink Palace Planetary Museum, Memphis, TN (2011)
A seismic refraction study of the Cocos plate offshore Nicaragua and Costa Rica, UT Arlington, Arlington, TX (2011)