Spatial migration of earthquakes within seismic clusters in Southern California: Evidence for fluid diffusion

摘要: [1] Seismicity within many earthquake swarms is observed to migrate slowly with time, which may reflect event triggering due slow fault slip or fluid flow. We search for this behavior in Southern California by applying a weighted least squares method quantify migration 69 previously seismicity bursts. obtain best-fitting directions and velocities, compute statistical significancesm each burst using bootstrap resampling method. define 37 bursts sm ≥ 0.8 as the group, 32 sm < 0.8 non-migration group. To explore differences between two groups, we effective stress drop (Δσquasi, ratio total moment radius), skew of release time series (μ), timing largest (tmax), distance separation first half second sequence (ds). As expected, group features larger ds lower Δσquasi, consistent higher significance. It also μ tmax, similar observations from Salton Trough, while more main shock-aftershock sequences. possible involvement, model diffusion equation, identify 18 coefficients ranging 0.01 0.8 m2/s, majority below 0.16 m2/s. The obtained are Reservoir-induced beneath Acu reservoir Brazil. normal faulting events associated these bursts, has most reverse events, indicating link type focal mechanism.