An improved version of the Load/Unload Response Ratio method for forecasting strong aftershocks

摘要

Temporal clustering and spatial concentration of aftershock sequences can be observed after the occurrence of most major earthquakes. Earthquake clustering effects, such as the rapid decay of aftershocks and second-stage aftershocks, cause large fluctuations in the Load/Unload Response Ratio (LURR). In order to eliminate the influence of such clustering, we introduce a new formula for calculating the LURR, taking the epidemic-type aftershock sequence (ETAS) model as the baseline seismicity model. We have applied the new formula retrospectively to the Wenchuan earthquake sequence in 2008 in China. The results show that the LURR increases slowly to a peak and then decreases sharply before strong aftershocks and that the new LURR performs better than the original LURR.