TURKEY was struck by a 50-day long 5.8 magnitude earthquake which remarkably nobody felt, research reveals.
via Express UK:
The rare event occurred in Istanbul during the summer of 2016 and lasted an incredible 50 days, according to a new study in Earth and Planetary Science Letters. The “phantom quake” has left geologists stunned and it is believed to have been caused when a fault line running under the Sea of Marmara slipped, leading to a slow earthquake. In most instances deadly earthquakes are caused when two tectonic plates that are sliding in opposite directions along the fault stick and then slip suddenly.
Meanwhile slow earthquakes happen in more stable regions around the fault and can release similar amounts of energy over a prolonged period.
The study, conducted by Patricia Martínez-Garzón and her team, used boreholes in the Sea of Marmara filled with strain metres that picked up this surface disturbance.
She told National Geographic: “You could call them phantom quakes.”
Lucile Bruhat, an earthquake physics researcher at the Ecole Normale Supérieure in Paris, said these reactions are “very common” and are “most of the time harmless”.
Attempting to explain the science behind the phenomenon, she added: “A good analogy for that is when someone walks on a wooden floor on the floor above.
“We can’t see them, but we can track the motion using the sounds of the wood cracking.”
Ms Bruhat also said the longest slow slip event ever recorded was in Alaska, and it produced a magnitude of 7.8 that took at least nine years to come to an end.
These incidents are more common in North America with the province of Cascadia known to register slow slip earthquakes with a magnitude of 6.0 which can last two or three weeks and repeat every 15 months.
Meanwhile in the New Zealand capital city, Wellington, a magnitude of 7.0 has been recorded but as they usually take 12-18 months to take place they once again go unnoticed.
A link between these small scale eruptions and larger disruptions is yet to be established.
Ms Bruhat added: “We have no idea how to distinguish an ultra-rare slow slip event that would trigger a large earthquake from a harmless one.”