New GPS study shows promise for 2-hour earthquake prediction signal

Previous studies have hinted at the existence of a precursory phase of slow aseismic slip in faults before major earthquakes. Aseismic slips are slow, almost imperceptible movements along a fault plane that do not cause detectable ground shaking. 

However, their connection to seismic ruptures — which do cause rapid and abrupt movement — remains unclear. Additionally, aseismic slips often occur without being followed by an earthquake.

In an attempt to shed light on this puzzle, Quentin Bletery and Jean-Mathieu Nocquet from Côte d'Azur University, France, conducted a systematic global search for short-term precursory fault slip before large earthquakes. 

Utilizing high-rate GPS time series data from over 3,000 geodetic stations worldwide, they measured fault displacement leading up to 90 magnitude seven and above earthquakes.

Their analysis revealed a subtle yet crucial signal —a period of exponential acceleration of fault slip near the hypocenter of the eventual earthquake, occurring approximately two hours before the rupture. 

According to the researchers, these findings suggest that many large earthquakes may initiate with a precursory phase of slip or that the observations represent the tail end of a much longer and more challenging-to-measure process of precursory slip.

What's holding earthquake predictions back?

While their study offers promising evidence of a potential precursory signal before large earthquakes, Bletery and Nocquet express their cautions. 

They highlighted that existing earthquake monitoring instruments lack the coverage and precision needed to identify or monitor for precursory slip at the scale of individual earthquakes.

Bürgmann also stated that it is still uncertain whether such slow-slip accelerations are distinctively associated with large earthquakes or whether they could be accurately measured for individual events to provide actionable warnings.

As the quest for earthquake prediction continues, these findings at least mark a significant step towards unraveling the mysteries surrounding precursors. 

As technology and understanding advance, the hope of issuing life-saving earthquake warnings may one day become a reality. However, for now, preparedness (where possible) and building resilient communities remain the best defense against these unpredictable forces of nature.

The complete study was published in Science on July 20.