2.59 K. Sadigh (1987) reported in Joyner and Boore (1988)

• Ground-motion model is:

  where y is in g. For strike-slip earthquakes: b = 1.1, c₁ = 0, c₂ = 2.5, for PGA at soil sites a = -2.611 and d = -1.75, for M < 6.5 h₁ = 0.8217, h₂ = 0.4814 and for M ≥ 6.5 h₁ = 0.3157 and h₂ = 0.6286, for PGA at rock sites a = -1.406 and d = -2.05, for M < 6.5 h₁ = 1.353 and h₂ = 0.406 and for M ≥ 6.5 h₁ = 0.579 and h₂ = 0.537. For reverse-slip increase predicted values by 20%. For M < 6.5 σ = 1.26 - 0.14M and for M ≥ 6.5 σ = 0.35.

• Uses two site categories:

  1.

  Soil

  2.

  Rock

• Use two source mechanism categories:

  1.

  Strike-slip

  2.

  Reverse-slip

• Supplement data with significant recordings of earthquakes with focal depths < 20km from other parts of world.
• Different equations for M < 6.5 and M ≥ 6.5.