Week 2

  1. What are large magnitudes of shear-wave splitting and orientations of fast polarization parallel to the Alpine fault shown?

  2. What happen for oceanic lithosphere when we have much greater creep strength of olivine than of crustal minerals?

  3. What are the two processes that can align anisotropic minerals?

2006-07

1. What are large magnitudes of shear-wave splitting and orientations of fast polarization parallel to the Alpine fault shown?


The large magnitudes of splitting (dvs /vs 4%) with the orientations of fast S-wave polarizations nearly parallel to the plane of simple shear imply shear strain corresponding to d/W > 1.5 and perhaps much larger. The nearly parallel orientations of fast polarization at sites 100 to 150 km southeast of the Alpine fault and at comparable distances northwest of its projection into both the northern South Island and the North Island (Fig. 3) indicate that strain has occurred over a zone at least as wide as 300 Km.


2. What happen for oceanic lithosphere when we have much greater creep strength of olivine than of crustal minerals?

The much greater creep strength of olivine than of crustal minerals makes oceanic lithosphere strong in the depth range where continental lithosphere appears to be weakest (1).
 

3. What are the two processes that can align anisotropic minerals?
Two processes can align anisotropic minerals: rotation of crystals in a finite strain field and dynamic recrystallization.
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1. why the strain due to horizontal shortening of the lithosphere, was ignored by the authors although the strain was one of absorbtion factor in the lithosphere?
Because that strain is smaller than the strike-slip shear and in part because pure flattening deformation induces smaller anisotropy than simple shear.

2. What would Lithospheric thickening by pure shear produce?Lithospheric thickening by pure shear would produce a high-speed zone in the upper mantle beneath the thickest crust.


3. By how many seconds the recrding of P-wave was delaying by lines of seismographs across the Southern Alps (11) ?
P-wave delays recorded by lines of seismographs across the Southern Alps (11) differ by up to 1 s from those expected for propagation through the laterally varying crustal structure

 

Questions or Comments?
Contact:
Dr. Ali O. Oncel