All rights reserved. No part of this publication may be reproduced or transmitted, in any form or by any means, without permission.Cover: Hanne Baadsgaard Utigard. Print production: Reprosentralen, University of Oslo.iii "A geophysicist is a person who passes as an exacting expert on the basis of being able to turn out with prolific fortitude infinite strings of incomprehensible formulae calculated with micrometric precision from vague assumptions, which are based on debatable figures taken from inconclusive experiments, carried out with instruments of problematic accuracy by persons of doubtful reliability and questionable morality for the avowed purpose of annoying and confounding a hopeless chimerical group of fanatics known as geologists who are themselves the lunatic fringe surrounding the hard working mining operator"

Abstract:The Nanga Parbat Massif (NPM), Pakistan Himalaya, is an exhumed tract of Indian continental crust and represents an area of active crustal thickening and exhumation. While the most effective way to study the NPM at depth is through seismic imaging, interpretation depends upon knowledge of the seismic properties of the rocks. Gneissic, 'mylonitic' and cataclastic rocks emplaced at the surface were sampled as proxies for lithologies and fabrics currently accommodating deformation at depth. Mineral crystallographic preferred orientations (CPO) were measured via scanning electron microscope (SEM)/electron backscatter diffraction (EBSD), from which three-dimensional (3D) elastic constants, seismic velocities and anisotropies were predicted. Micas make the main contribution to sample anisotropy. Background gneisses have highest anisotropy (up to 10.4% shear-wave splitting, AVs) compared with samples exhibiting localized deformations (e.g. 'mylonite', 4.7% AVs; cataclasite, 1% AVs). Thus, mylonitic shear zones may be characterized by regions of low anisotropy compared to their wall rocks. CPOderived sample elastic constants were used to construct seismic models of NPM tectonics, through which P-, S-and converted waves were ray-traced. Foliation orientation has dramatic effects on these waves. The seismic models suggest dominantly pure-shear tectonics for the NPM involving horizontal compression and vertical stretching, modified by localized ductile and brittle ('simple') shear deformations.

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