  Mainshocks are often followed by increased earthquake activity (aftershocks).
According to the Omori-Utsu law, the rate of aftershocks decays as a power law
over time. While aftershocks typically occur in the vicinity of the mainshock,
previous studies have suggested that mainshocks can also trigger earthquakes in
remote locations. Here we examine the earthquake rate in the days following
mega-earthquakes (magnitude >= 7.5) and find that the rate is significantly
lower beyond a certain distance from the epicenter compared to surrogate data.
However, the remote earthquake rate after the strongest earthquakes (magnitude
>= 8) can also be significantly higher than that of the rate based on surrogate
data. Comparing our findings to the global ETAS model, we find that the model
does not capture the earthquake rate found in the data, hinting at a potential
missing mechanism. We suggest that the diminished earthquake rate is due the
release of global energy/tension subsequent to substantial mainshock events.
This conjecture holds the potential to enhance our comprehension of the
intricacies governing post-seismic activity.
