1Geometry of Deformation1Geol341/342-Structural GeologyOutline• Kinematic Analysis• Deformation– Rigid Body Deformation• Translation• Rotation• Displacement Vectors- Strain paths– Non Rigid Body Deformation (Distortion)• Dilation- change in volume• Distortion- change in shapeKinematic Analysis• The study of the movements of rock during deformation• Deformation= Change in shape, volume, or position of a body [due to an applied stress].Kinematic AnalysisRigid Body Deformation• Particles in a body do not change relative positions– Translations– RotationsRigid Body TranslationDefine frame of referenceYXYo+nXo+mXoYomnDisplacement vectorVectors vs. Scalars• Displacement vectors– Direction of movement– Distance2Dike IntrusionDike IntrusionFinite Displacement VectorsDike IntrusionDisplacement Path vs.Displacement VectorsFault Striations- Last recorded motionFixedFault=displacement discontinuity3Southern California GPS Velocity FieldVelocity Relative to North AmericaRigid Body RotationDefine frame of referenceYXDisplacement pathW(Xo,Yo)(X1,Y1)X1=(CosW)Xo+(SinW)YoY1=-(SinW)Xo+(CosW)YoRotation AxisAll Plate Motions are RotationsMotion with respect to what?v= risin Θ4Non-Rigid Body DeformationDistortion (Strain)•Change in Volume (Dilation)•Change in Shape Homogeneous vs. Heterogeneous DeformationStrain EllipseUndeformedDeformedPrincipal Strain Axes5Non-Coaxial and Coaxial StrainExtension QuadrantShortening QuadrantNo change in lengthCoaxial Strain (Pure Shear)Particle Paths6Coaxial StrainNon-Coaxial
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