?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F123%2F&rft.title=On+Seismic+Imaging%3A+Geodesics%2C+Isochrons%2C+and+Fermat's+Principle&rft.creator=Webster%2C+Paul&rft.subject=Energy+and+utilities&rft.subject=None%2FOther&rft.description=Analytic+expressions+are+derived+for+the+isochrons+in+an+inhomogeneous+medium+characterized+by+a+linear+velocity+gradient+and+for+an+anisotropic+medium+characterized+by+an+elliptical+velocity+dependence.+The+results+were+generated+for+a+single+surface+source+and+five+wellbore+receivers+over+a+dipping+interface.+The+traveltime+and+reflection-point+results+appear+to+be+sensitive+to+a+given+assumption+of+the+velocity+field.+In+complex+geological+areas+the+location+of+the+planar+reflector+is+tangent+to+the+convex+hull+of+isochrons+and+might+not+correspond+to+their+intersection+points+since+the+two+concepts+need+to+coincide.&rft.date=1998-06-05&rft.type=Study+Group+Report&rft.type=NonPeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fmiis.maths.ox.ac.uk%2Fmiis%2F123%2F1%2Fgeomechanics.pdf&rft.identifier=++Webster%2C+Paul++(1998)+On+Seismic+Imaging%3A+Geodesics%2C+Isochrons%2C+and+Fermat's+Principle.++%5BStudy+Group+Report%5D+++++