Is there any correlation between La Nina and El Nino and seismic activity?

Question

I've read in the past that extreme precipitation levels may have an effect on seismic activity, and wondered if anyone has ever analysed the La Niña / El Niño cycles to see if there are any correlations with seismic activity in the area affected by the phenomena.

Answer 1

While it may seem counterintuitive that atmospheric phenomena like El Niño and La Niña (ENSO) could affect the solid Earth, scientific research suggests there is indeed a subtle, indirect correlation between extreme climate cycles and seismic activity.

The primary mechanism for this link is hydrogeological loading and pore pressure changes. During extreme ENSO phases, certain regions experience massive increases in precipitation. For example:

1. Mass Loading: The weight of massive amounts of rainwater or snowpack on a tectonic plate can actually deform the Earth's crust slightly. This "loading" can increase the stress on pre-existing faults.
2. Pore Pressure: As heavy rainwater infiltrates deep into the ground, it can increase fluid pressure within fault zones. This "lubricates" the fault, potentially triggering a seismic slip that was already near its breaking point.
3. Atmospheric Pressure Changes: Studies have also looked at how significant changes in sea-level atmospheric pressure during ENSO cycles can slightly alter the stress state on shallow undersea faults, particularly in the Pacific Basin.

However, it is important to note that correlation does not always mean direct causation. ENSO does not "create" earthquakes; rather, it may act as a subtle "trigger" or "modulator" for seismic events that were already geologically imminent. Most tectonic activity is driven by internal planetary heat and plate movements, which operate on a much larger scale than atmospheric cycles.