Tectonic strain loads the fault at a constant rate; shear stress σ rises linearly (σ += rate·dt) while friction locks the fault. Once σ reaches the fault's frictional strength τ, the fault ruptures instantly ("stick-slip"): stress drops to a residual value and a slip increment is released, offsetting the marker bed. Slip geometry follows the dip angle δ:
throw = slip · sin(δ) (vertical offset)
heave = slip · cos(δ) (horizontal offset)
net slip = √(throw² + heave²)
Each rupture's size is converted to a moment magnitude with the real Hanks–Kanamori relation used by seismologists, using the rupture length you set (fault width assumed ≈ length/2, shear modulus μ = 30 GPa, typical continental crust):
M0 = μ · A · D (seismic moment, N·m)
Mw = (2/3)·log10(M0) − 6.07
A steeper dip (higher δ) makes throw dominate over heave — a near-vertical fault (δ→90°) offsets strata almost purely vertically, while a shallow thrust (δ→20–30°, typical of reverse faults) produces large heave for the same slip. Normal faults drop the hanging wall down-dip (extension); reverse faults push it up-dip (compression); strike-slip switches to map view, where blocks slide laterally past each other along a near-vertical fault with no vertical throw at all — a channel bent across the fault trace shows the lateral offset directly.