Understanding Source Time Functions
The Source Time Function (STF) describes how seismic moment is released over time during an earthquake. It provides crucial insights into rupture dynamics and earthquake physics.
Key Components:
- Moment Rate Function: Rate of seismic moment release (red curve)
- Cumulative Moment: Total moment released up to any time (blue curve)
- Rise Time: Time for slip to reach maximum at any point
- Rupture Duration: Total time for the entire rupture process
Model Types:
- Simple Pulse: Single smooth moment release
- Brune Model: Exponential decay, common for small earthquakes
- Complex: Multiple sub-events, typical of large earthquakes
- Bilateral: Rupture propagates in both directions from hypocenter
Physical Meaning: The STF reflects fault heterogeneity, stress distribution, and rupture dynamics. Simple earthquakes show smooth functions, while complex events reveal multiple asperities and barriers.