Earthquakes in Turkey and Syria: a Q&A with geophysicist Rob Govers
Recap of the 14 February online lecture 'The science behind an earthquake'
Last week, Utrecht University hosted an online lecture on the 6 February 2023 earthquakes in Turkey and Syria. After acknowledging the overwhelming suffering of those affected, geophysicist Rob Govers explained the science of earthquakes: why specifically this location was hit, what exactly happened during the earthquakes, and why certain earthquakes are so much more devastating than others. His lecture was followed by a Q&A with questions from viewers. Here, we bundle the main questions and answers.
There are several fault lines running through Turkey. One of those fault lines is the North Anatolian Fault, which is under a lot of tension. A viewer asks: due to that tension, is there a larger earthquake risk?
In the north, tension indeed builds faster than in the east, but earthquakes are also more frequent there. It seems that this creates a kind of balance. Larger earthquakes have often occurred in the north, for example in 1939 in Turkey. Both fault lines can create similar earthquakes, but they are more frequent in the north.
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A person living in Istanbul asks: for years, there's been predictions that a large earthquake will hit Istanbul. Can you make a prediction of when?
Unfortunately not. That is the reality of earthquake science right now. We have been looking at many precursors – things that happen before earthquakes – that would help to predict whether an earthquake would occur. There are other aspects of earthquakes that we do have a sense of like the magnitude, the type of earthquake, and the risk of damages to your house in a forty-year period. This is useful because it gives you the opportunity to take precautions: move further away from a fault line, reinforce your house, or get insured. But the timing is something that we cannot predict.
Govers talks about the second earthquake likely being triggered by the first one. Can these earthquakes affect the North Anatolian Fault line?
The stress effect of both 6th February earthquakes was calculated by Temblor. The zones that they calculated are expected to experience earthquakes in the future. Those zones are rather regional, they don’t extend all the way to Istanbul. That’s why I don’t expect these earthquakes to have a significant effect on the imminent earthquake that should be expected in Istanbul.
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How were experts so quick in predicting the casualties and economical damage right after the earthquakes?
These predictions are based on a vast amount of information that is being collected by geologists, seismologists, geophysicists. They accumulate the type of information that is needed to make such a prediction before an earthquake even happens. Whenever there is an actual earthquake, the data from that earthquake is automatically put into a model that estimate the casualties and economic damage. The model includes information about the quality of buildings in particular cities and countries, for example.
Some experts say that planetary positions have an effect on earthquakes. Is this true?
The fair answer is ‘I don’t think so’. The best answer is for me to explain how we go about predicting earthquakes. We have a record of earthquakes, which means that we know when earthquakes in a particular area occurred. You can compare that record to the planetary positions and whether they had a significant change in gravity or electromagnetics for that specific area. If you see a correlation, then you would need to examine this further. However, historically there has also been a correlation with barking dogs and earthquakes – but the problem is that dogs would also bark if there was no earthquake. So you have to be careful with predictions like these. So far we have not found anything that is predictive in the sense of planetary positions.
Is it true we no longer use the Richter Scale?
Yes. The Richter scale was based on measuring the maximum amplitude of the waves that came in to the data stations. That maximum amplitude was then translated into the magnitude of the earthquake. New measuring equipment picks up waves on a much broader spectrum than older equipment – they are much more sensitive and accurate. You could rescale this data to the old Richter scale. However, the Richter scale has drawbacks in the sense that it is based on California. California has a different geology and smaller earthquakes than, for example, Turkey. The old measuring equipment was only able to measure up to a certain amplitude, and was only able to record earthquakes with a magnitude of 7 to 7.5. So it does not work properly for the rest of the world.
The new scale, Moment Magnitude, no longer works with amplitude, but it makes an estimate of the energy that is released at the source. That number is calculated in a way that it corresponds to the Richter scale, but goes beyond the 7.5+ magnitudes that the Richter scale could not account for.