Deformation Pattern in an Earthquake Source Region

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This Demonstration gives a three-dimensional illustration of the deformation pattern that develops during an earthquake rupture in the immediate vicinity of the source. You can define the strike, dip, and slip angle of the fault as well as the amount of slip.


As a result of the slip, the four segments of the sphere are deformed differently. The white ones are compressed while the orange ones are dilated. This effect is shown through a change of their sizes as a function of slip. This spatially anisotropic deformation pattern causes an anisotropic radiation of seismic energy in the form of seismic waves.


Contributed by: Frank Scherbaum,Nicolas Kuehn, and Björn Zimmermann (March 2011)
Open content licensed under CC BY-NC-SA



During an earthquake rupture, strained blocks of rock material rapidly move against each other. During this process, the immediate vicinity of the earthquake hypocenter, usually illustrated as an imaginary sphere of unit radius (focal sphere), is deformed in a quadrilobed pattern. Two quarters of this sphere (white) undergo compression while the two others (orange) are relaxed. The orientation of these quarter-spheres in space depends on the geometry of the earthquake fault and the direction of slip (vector ) on it. The orientation of maximum compression is called the axis while the direction of maximum dilatation is called the axis.

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