Theory 011/Earth & Space /Seismology
Fault Recurrence Is Set by Roughness
Recurrence is computed from slip rate. The fault's texture may decide how much stress it can store.
Earthquake recurrence intervals on a fault are set by its roughness rather than by loading rate, so a rough fault with fast loading can rupture less often than a smooth fault with slow loading.
01The evidence
Recurrence intervals vary by more than loading rates explain, and roughness has been linked to the size and frequency of ruptures in fault studies.
02The tension
Recurrence is estimated by dividing accumulated slip by slip rate. That assumes every patch fails at the same stress, which roughness contradicts.
03The mechanism
A rough fault has patches that lock at different stresses. Ruptures must break through the strongest patch, which sets the interval, and a rougher fault spends longer accumulating the stress needed to do so.
That makes roughness a multiplier on the loading rate, which predicts scatter in recurrence that loading alone cannot produce.
04What this is not
Slip-rate models divide slip by rate. This multiplies by a roughness factor, which explains the scatter.
05Predictions
- P1Recurrence should correlate with roughness at similar slip rates.
- P2Rough faults should show more variable intervals.
- P3Rupture extent should be limited by the strongest barrier.
06Refutation
Recurrence tracking slip rate at controlled roughness would restore the simple division.
07What it changes
It would put fault geometry into hazard estimates.