Focal Mechanism Inversion

Fault plane

Focal Mechanism Beachball

Radiation pattern

How to determine focal mechanism?

Review: Inverse Problems in Geophysics

• Forward function: last lecture
• Objective/Loss function
• Gradient
• Optimizer

Focal mechanism from first motion polarity

• FPFIT

Objective/Loss function:

are the observed and theoretical first-motion polarity (0.5 for compression, -0.5 for dilatation).
is the square root of the normalized theoretical P-wave radiation amplitude of earthquake recorded at the station for source model .

Focal mechanism from first motion polarity

• HASH