Dislocation in Elastic Halfspace Model of the Earthquake18

# Dislocation in Elastic Halfspace Model of the Earthquake18...

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12.005 Lecture Notes 18 Dislocation in Elastic Halfspace Model of the Earthquake Cycle Interseismic: Slip below depth D Figure 18.1 Coseismic: Region above D “catches up” Figure 18.2 X/D Strain Displacement -15 -10 -5 5 10 15 y X/D -3 0 ε xy 3 -3 -15 -10 -5 5 10 15 0 X/D 3 y X/D ε xy Figure by MIT OCW. Figure by MIT OCW.

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Displacements from Earthquakes, Fault Slip, etc Consider a strike-slip fault with displacement S, independent of depth – A screw “dislocation” – i.e., a slip discontinuity. Original ring (dashed) becomes helix (solid). Figure 18.3. Section across a mathematical model of a transcurrent fault. “Dislocations” are used to describe defects in crystals, as well as fault motions. A crystal disrupted by a screw dislocation is shown in the figure below. 1 2 D D i s l o c a t n x S/2 S/2 Fault displacement S S u r f e x 3 x 2 x 1 Figure by MIT OCW.
Figure 18.4. A screw dislocation in a cubic lattice constitutes a deformation that is out of the plane of atoms illustrated. The two atoms denotes by solid circles are essentially part of a second plane. The Burgers circuit indicated by the numbered

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Unformatted text preview: steps naturally moves into this second plane. Therefore in order to close the circuit the Burgers vector b* must be perpendicular to the plane of atoms shown. Types: Figure 18.5 7 6 5 4 3 2 1 10 b * 8 9 Screw Edge Figure by MIT OCW. Figure by MIT OCW. Figure 18.6 Side view of an edge dislocation in a cubic lattice. Dislocation motion helps crystals deform (don’t all have to slip at one time). Also helps Earth deform! Figure 18.7 A dislocation. b * 2 1 3 4 5 10 9 6 7 8 1 2 3 4 5 10 9 8 7 6 C D E A S B Figure by MIT OCW. Figure by MIT OCW. Figure 18.8 Upper group: Slip by propagation of an edge dislocation EE. Lower group: Slip by propagation of a screw dislocation SS. E C A b b B E E E S S S S B A C Figure by MIT OCW. Figure 18.9 Displacement as a function of distance from a transcurrent fault. 1 2 2 4 6 8 10 Displacement (meters) Distance from fault (km) NE Figure by MIT OCW....
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## This note was uploaded on 10/25/2010 for the course MIT Geodynamic taught by Professor Ywn during the Fall '10 term at MIT.

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Dislocation in Elastic Halfspace Model of the Earthquake18...

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