Along-strike stress delays the ordering of slip on a fixed-length fault

Wenjie Lyu 

The size of a large earthquake depends on how far the rupture runs and how much the fault slips. An early correlation with magnitude can appear while those two contributions are still mixed. Patches at both ends stop every rupture on a 120 km fault, so the length no longer varies and the early order is an order of slip. One background stress is a single value along the fault, and the other also varies along strike. Slip at 20 s is ordered by 2 s for 259 ruptures in the first case, and by 8 s (7-9 s) for 230 ruptures in the second. The extra seconds are not a slower rupture front. Where the stress varies along strike, stations beside the fault and around it show that order when the waves arrive. Stations ahead of the rupture do not lead the waves, and where the stress is one value, stations around the fault are later than the waves. The calculations are an idealized two-dimensional dynamic simulation, with one friction law and no field record.