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Latitude, Free-air, Bouguer, Terrain. Depth, density difference (not absolute density) Further from (a) Distance between two satellites. Example of issues with choice of model. Generate data using sphere. g z =4/3 p GR 3 Dr z(x 2 +z 2 ) -3/2. Find best-fit model using infinite cylinder.
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Depth, density difference (not absolute density) • Further from • (a) Distance between two satellites
Example of issues with choice of model Generate data using sphere gz=4/3pGR3Drz(x2+z2)-3/2 Find best-fit model using infinite cylinder gz=2pGR2Drz(x2+z2)-1
Why are there anomalies? 1. Very recent changes (still sinking/rising) 2. Dynamic processes in mantle (rising plumes) 3. Flexure of “strong” lithosphere (section 5.7) Volcano, subduction zone Oceanic crust Example: cantilevered beam, fixed at one end
Compare thickness of seismic and elastic lithosphere: Lseismic can break in earthquakes (short timescale), but doesn’t contribute to flexural strength.
Compare thickness of seismic and elastic lithosphere: Lseismic can break in earthquakes (short timescale), but doesn’t contribute to flexural strength.
Earthquakes 1963-1995; mb > 4 DIFFUSE BOUNDARY ZONES INTRAPLATE NARROW BOUNDARIES Stein and Wysession, 2003
relative plate velocities based on seafloor spreading rates and directions plus directions from earthquake slip vectors Plates relative to eachother (cm/yr)
NNR-NUVEL-1A Plates relative to “average”
Absolute plate motions • Set of hot spot tracks on seafloor provide global reference frame • On Pacific plate, many show same changes in direction, indicating same relationship to plate motion
Absolute plate motions • Set of hot spot tracks on seafloor provide global reference frame • On Pacific plate, many show same changes in direction, indicating same relationship to plate motion
Cenozoic Mesozoic Paleozoic Precambrian