Block Models as a Tool for GPS Analysis

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Block Models as a Tool for GPS Analysis

• An example from the eastern Mediterranean

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Seismicity and earthquake focal mechanisms
provide a first-cut for block boundaries
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GPS velocities refine the boundaries
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Region is divided into blocks, contiguous areas
that are thought to rotate rigidly.
The relative long-term slip vectors on the faults
are determined from rotation poles.
Each block rotates about a pole.
Back-slip is applied at each fault to get surface
velocities due to locking.
Velocities due to fault locking are added to
rotations to get full velocity field.
Courtesy Rob McCaffrey
The rotating blocks are separated by dipping
faults.
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Okada model applied at boundaries
Model velocities same for any path integral
Meade et al., 2002
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• GPS velocities
• observed
• modeled
• block motion

Residuals
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Data
Program Flow for DEFNODE
Parameters

• GPS velocities
• Uplift rates
• Tilt rates
• Slip vectors
• Transform azimuths
• Spreading rates
• Fault slip rates
• Strain rates

Block rotations Reference frame Fault
locking Uniform strain rates
Output
Text files GMT mappable files Uncertainties
(linearized)
Solution
Grid search Downhill simplex
McCaffrey 1995 2007