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To better predict an incoming megaquake, scientists have discovered a particular indicator that pops up just seconds after the tremor starts.
Unlike an oncoming hurricane, earthquakes are significantly harder to predict, making any early warnings almost impossible. However, researchers from the University of Colorado have trawled through huge seismic datasets to discover a potential telltale clue that a megaquake – magnitude 7 or higher – has just happened.
In a paper published to Science Advances, the scientists combined databases of earthquakes dating back to the 1990s to show that this sign appears between just 10 and 15 seconds after the beginning of a megaquake.
This marks the moment when a new earthquake transitions into a slip pulse, where mechanical properties point to magnitude. Importantly, the researchers were also able to spot similar trends in data obtained from Europe and China.
Diego Melgar, who was involved in the discovery, said that for him, “the surprise was that the pattern was so consistent”.
Overall, the databases contained information on more than 3,000 earthquakes, with displacement acceleration appearing between 10 and 20 seconds in 12 major earthquakes between 2003 and 2016.
Overcoming delay
Key to the breakthrough were GPS monitoring sites dotted along many land-based faults, but so far their use has not expanded to live hazard monitoring for earthquakes.
“As an earthquake starts to move, it would take some time for information about the motion of the fault to reach coastal stations,” Melgar said. “That delay would impact when a warning could be issued. People on the coast would get no warning because they are in a blind zone.”
To solve this delay, sensors would need to be placed on the seafloor to record the early telltale sign and, if this data was available in real time, it could make early-warning systems much more accurate.
However, Melgar has noted that such work is expensive and even more so for installing the technology on the seafloor above the Cascadia fault zone off the western coast of the US.
