Intraplate earthquakes are seismic events that occur within the stable interiors of tectonic plates, far from the active boundaries where most earthquakes originate. Prof Éric Calais and Jean François Ritz highlight the unpredictable nature of these quakes, which can strike unexpectedly in geologically quiet regions.
Unlike boundary-related earthquakes where the tectonic mechanisms are well-understood and monitored, intraplate earthquakes occur on faults that are less active and poorly documented. For example, since 1974, only about 20 significant intraplate earthquakes of magnitude 6 and above have been recorded. This low frequency complicates efforts to gather enough data to accurately predict when and where the next event might occur. The difficulty in predicting these earthquakes stems from the absence of a comprehensive historical record and the deep, often unknown faults that may activate after millennia of dormancy.
The mechanism of fault rupture for intraplate quakes can be similar to that at tectonic boundaries—strain accumulates over time until the geological fault ruptures, releasing energy as seismic waves. However, the triggers for these ruptures in plate interiors may differ, influenced by factors such as the unloading of the crust due to ice melt or changes in surface erosion, rather than the movement of plates themselves. This complexity adds another layer of challenge in forecasting these events.
The consequences of not being able to predict intraplate quakes are severe, especially as urban areas within historically stable continental interiors grow in size and population. The 2019 Le Teil earthquake in France and the devastating 2001 quake in Gujarat, India, illustrate the potential for significant damage and loss of life. In both instances, the affected areas were not known to be at high risk for earthquakes, highlighting the critical need for better predictive models.
The difficulties of earthquake prediction are compounded by the possibility of “orphan” events—quakes that result from the reactivation of ancient faults with no prior history of activity. Without previous seismic records, these faults remain hidden until an unexpected rupture occurs, posing a significant challenge to seismologists trying to forecast future events.
To address these challenges, researchers like Calais and Ritz are advocating for increased monitoring and research into the mechanisms and potential triggers of intraplate quakes. This includes studying the effects of environmental changes, such as glacial melting and erosion, on seismic activity. Despite the inherent difficulties, understanding and eventually predicting intraplate earthquakes remains a critical area of focus in global earthquake preparedness and disaster mitigation efforts.
https://www.sciencefocus.com/planet-earth/strange-earthquakes