Harm Van Avendonk, UTIG SResearch Scientist
Harm Van Avendonk
PhD., 1998, Scripps Institution of Oceanography, UC San Diego
B.S., 1993, Geophysics, Utrecht University, the Netherlands
email: harm at ig.utexas.edu
Harm's main scientific interest is the deep crustal 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 involves the Eastern North American Margin where he is involved in the Community Seismic Experiment.
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 fracturing 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. To explain this apparent paradox, differentiation and reworking of arc crust upon accretion to continents have been proposed.