The 7.5-magnitude temblor that struck Turkey on Monday after the 7.8-magnitude quake was an unusually strong aftershock, according to seismologists.
Aftershocks are typically about 1.2 magnitude units lower than the original quake, a statistic theory shows The magnitude 7.5 jolt that hit Turkey at 1:24 p.m. local time, just over nine hours after the initial quake, was just 0.3 units smaller.
That made the force of the shock remarkable on its own, as well as relative to the main quake, experts said.
«In the most general terms, a mainshock typically has an aftershock that is an order of magnitude smaller. So, for example, on average, a magnitude 8 earthquake has an aftershock that is magnitude 7,» said Dara Goldberg, EE geophysicist. U.S. Geological Survey.
There are still likely many smaller aftershocks, he added.
«As we start to see how this aftershock sequence plays out, we’ll have better estimates of how long and how productive we expect this sequence to be,» Goldberg said. «But unfortunately, the reality is that there will certainly be aftershocks and hopefully they won’t significantly impede rescue efforts.»
In magnitude measurements of the size of an earthquake, each whole number represents a 10-fold increase from the bottom number. Magnitude 7 earthquakes in populated areas are rare but devastating: In August 2021, a magnitude 7.2 earthquake in Haiti killed more than 2,100 people. A magnitude 5.8 aftershock followed.
Monday’s earthquake has killed more than 3,600 people in Turkey and Syria, and the death toll is expected to rise.
Seismologists said the magnitude 7.5 temblor that followed the initial quake qualified as an aftershock, not a separate quake, because it was encountered by an aftershock. rankings: Occurred within a fault line of the initial earthquake and was of minor magnitude. What will happen next is hard to predict.
«Every earthquake sequence is different,» said Gary Patterson, a geologist with the Center for Earthquake Research and Information at the University of Memphis. «The vast majority of the time, you’ll see the power of earthquakes decrease over time relative to the mainshock, and it could last for days, hours, months, or even years.»
Turkey is prone to high seismic activity because it is close to a «triple junction» where three of Earth’s tectonic plates meet.
«Wherever there are those boundaries, where two or, in this case, three plates meet, there is friction along that plate boundary, causing the Earth’s crust to bend and warp,» Goldberg said. «And eventually, enough pressure builds up for the plates to slide past each other.»
Could this earthquake increase the risk of more elsewhere?
Earthquakes and aftershocks of this intensity can occur anywhere on major fault lines, such as California, Alaska, and other parts of the United States. But Monday’s temblor is unlikely to trigger distant quakes.
«People always jump to the conclusion that it’s causing something else,» said Lucy Jones, a seismologist and chief scientist at the Dr. Lucy Jones Center for Science and Society.
In reality, the cascade of seismic activity after an earthquake is limited in its geographic extent, he said. But due to the multiple fault lines in Turkey, other areas of the country could experience earthquakes.
«There is going to be a higher risk of an earthquake,» he said. «It’s pretty small. But it’s real.»
There is much to learn from the Turkey earthquake investigation, Patterson said, particularly when it comes to saving lives in the future.
«Many engineers will study this earthquake to find out how the built environment can best survive these types of events,» he said.
Earthquakes do not have a particular season in which they are most likely, and climate change is generally not a contributing factor, the experts said.
As much as everyone would like to know reliably when they will strike, earthquakes happen randomly, Goldberg said.
«We never know what’s coming, which is a challenge for seismology in general,» he said.