Q: Two earthquakes occurred on the same day. Are they related?
A: Often, people wonder if an earthquake in Alaska may have triggered an earthquake in California; or if an earthquake in Chile is related to an earthquake that occurred a week later in Mexico. Over these distances, the answer is no. Even the Earth’s rocky crust is not rigid enough to transfer stress fields efficiently over thousands of miles.
Van der Elst, Nicholas. J. and Emily E. Brodsky, Long and short range earthquake triggering as a function of seismic wave amplitude, submitted to Science.