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dc.contributor.authorHirsch, Aaron C.en_US
dc.date.accessioned2016-03-22T18:56:17Z
dc.date.available2016-03-22T18:56:17Z
dc.date.issued2014
dc.identifier.urihttps://hdl.handle.net/2144/15254
dc.description.abstractThe standard model of the thermal and chemical structure of cratons has been scrutinized in recent years as additional data have been collected. Recent seismological and petrological studies indicate that the notion of cratonic lithosphere as a thick thermal boundary layer with a very depleted and dehydrated composition may be too simplistic and does not fully explain all aspects of the seismological and petrological observations. We hypothesized that the cratonic lithosphere may be more complicated and designed an experiment to investigate its thermal, chemical, and mineralogical properties using a global database of fundamental mode Rayleigh surface waves. To test this hypothesis, the phase velocities of Rayleigh wave that travel paths primarily over cratons were selected. A 1-D global craton phase velocity profile was generated from these observations and compared to predicted phase-velocity curves using two different forward modeling techniques. With the first approach, profiles of shear velocity were generated based on educated guesses of upper mantle temperatures using geotherms. With the second approach, profiles of shear velocity were generated using random permutations about 1-D global model STW105. In total 5,625 geotherm and 80,000 random 1-D forward models were generated for comparison. Each shear velocity model was converted to phase velocity and compared to the observed range of cratonic phase velocities, defined as within one standard deviation of the mean. This method was able to constrain shear velocity in cratons relatively well though the 1-D profiles deviate at depths shallower than 100 km. Shear velocity is faster than PREM/STW105 to depths greater than 200 km with constantly increasing velocity with depth in the random model and a low velocity layer at 100-150 km.en_US
dc.language.isoen_US
dc.subjectGeophysicsen_US
dc.subjectCratonen_US
dc.subjectGeothermen_US
dc.subjectModelen_US
dc.subjectPhase velocityen_US
dc.subjectShear velocityen_US
dc.subjectSurface wavesen_US
dc.titleConstraints on shear velocity in the cratonic upper mantle from Rayleigh wave phase velocityen_US
dc.typeThesis/Dissertationen_US
dc.date.updated2016-03-12T07:10:22Z
etd.degree.nameM.A.en_US
etd.degree.levelmastersen_US
etd.degree.disciplineEarth & Environmenten_US
etd.degree.grantorBoston Universityen_US


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