Another earthquake, of magnitude 5.6, hit the same southern regions of Turkey on 27 February 2023 where the massive death and destruction was caused by four major earthquakes on 6 and 7 February.
Since then, in a space of less than three weeks, more than 10000 aftershocks have been registered across the 11 provinces of Turkey, making it one of the longest series of seismic tremors recorded in the history.
Why are so many earthquakes happening in Turkey? — There can be many ways to answer this question but none of the answers would be adequately satisfactory.
Nonetheless, let us look at some of the explanations offered by the experts.
UNDRR (United Nations Office for Disaster Risk Reduction) is a globally respected body on earthquakes and other disasters, and how to deal with them.
An article written by Jenny Jenkins, and originally published by The Conversation on 7 February 2023, is available at the PreventionWeb, a website managed by the UNDRR. It offers some explanation.
Article by Jenny Jenkins
She writes, “This area of Turkey is prone to earthquakes as it lies at the intersection of three of the tectonic plates that make up the Earth’s crust: the Anatolian, Arabian and African plates. Arabia is moving northwards into Europe, causing the Anatolian plate (which Turkey sits on) to be pushed out westwards.”
“The movement of the tectonic plates builds up pressure on fault zones at their boundaries. It is the sudden release of this pressure that causes earthquakes and ground shaking,” Jenkins writes.
She explains, “This latest earthquake is likely to have happened on one of the major faults that marks the boundaries between the Anatolian and Arabian plates: either the East Anatolian fault or the Dead Sea Transform fault. These are both “strike-slip faults”, which means they accommodate some motion of plates moving past each other.”
Later in the article, Jenny Jenkins makes an important point: “We tend to think of earthquake energy as coming from a single location, or epicentre, but they are actually caused by movement along an area of a fault. The bigger the earthquake the larger the fault area that will have moved. For something as large as this magnitude 7.8 there is likely to have been movement over an area roughly 190km long and 25km wide. This means the shaking will be felt over a very large area.”
Her explanation of ‘aftershocks’ is also important: “After major earthquakes there will be many smaller earthquakes known as aftershocks as the crust readjusts to the changes in stress. These can continue for days to years after the initial event. In the first 12 hours after the initial tremor in southeast Turkey [on 6 February 2023] there were already three other earthquakes above magnitude 6.0. The first was a 6.7 which happened only 11 minutes after the first shock, and there have been hundreds of smaller magnitude aftershocks.”
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NC State University (College of Natural Resources) is another source that seriously deals with the related subjects. An article at their website, written by Andrew Moore and published on 23 February 2023, elucidates as to why these earthquakes in Turkey have been so deadly.
Why the Turkey-Syria Earthquakes Were So Destructive
Andrew Moore consulted Ms. Ashly Cabas, an assistant professor of civil, construction and environmental engineering and a fellow at the Center for Geospatial Analytics for the expert opinion.
Here are some parts of his conversation with Cabas:
Ashly Cabas said the sheer power of the recent earthquakes created the “perfect recipe for strong ground motions to take place.”
Cabas uses geospatial analytics to characterize earthquake ground motions and the effects of the spatial variability of sedimentary deposits on the intensity of ground shaking and deformation. More specifically, her research team develops predictive models of the response of soils and foundation systems to seismic loading.
“Because these shallow, large magnitude earthquakes had epicenters located nearby densely populated cities, along with a fault rupture spanning approximately 186 miles, many communities and civil infrastructure systems were exposed to strong ground shaking,” Cabas said.
She added, “I think the observations and analyses from reconnaissance teams in the field will provide much needed information to fully understand the compounding effects that led to the devastation the whole world is sadly witnessing in Turkey.”
Turkey is one of the world’s most active earthquake zones because it is located on the Anatolian plate, which is being squeezed westward by the northward collision of two tectonic plates — the Arabian and Eurasian.
As these plates move past each other, they get stuck at their edges due to friction and pressure builds up. When the pressure is finally released, an earthquake occurs, triggering waves of energy that cause the ground to shake.
Earthquake shaking causes horizontal and vertical motion that can lead to deformations in beams, columns and other structural elements in buildings. The degradation of the integrity of these structural elements can ultimately lead to collapse.
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An article written by Ms. Lizzy Rosenberg and published by GreenMatters on 21 February 2023, tries to shed some light on the burning question: Why does Turkey get so many earthquakes?
Why Does Turkey Get So Many Earthquakes? Residents Slammed by Yet Another Deadly Tremor
Though Turkey has a relatively extensive history of earthquake activity, the Eastern European nation has clearly been experiencing an influx of them in recent weeks. But a big earthquake was in Turkey’s future, according to seismologists, and it was going to happen sooner rather than later.
According to ABC News , Turkey lies atop four tectonic plates , with the Eurasian plates creating friction with the Arabian and African plates. ABC compares Turkey to a banana being squeezed from its peel.
“That stress is essentially squeezing Turkey out to the west into the Aegean,” St. Lawrence University geology professor, Alexander Stewart, stated via ABC News
And what’s more, Turkey is slipping along the world’s most seismically active fault zone, the North Anatolian fault zone and the the East Anatolian fault zone, which extend down through Syria. So it should come as no surprise Turkey is within the top 20 percent of countries to experience a deadly quake.
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It is not just Turkey and Syria. Noticeable earthquakes are happening on almost daily basis in many other parts of the world.
So, can we predict earthquakes?
Another article at The Conversation and republished on 16 February 2023 by phys.org under the Creative Commons license, attempts to answer this question. It is written by Harold Tobin. He is University of Washington professor of seismology and geohazards, and heads the Pacific Northwest Seismic Network.
Earthquake prediction is not possible, but longer-term forecasts and brief warnings after one starts are
Here are some passages from the article by Tobin:
Can scientists predict a particular earthquake? — In short, no. Science has not yet found a way to make actionable earthquake predictions. A useful prediction would specify a time, a place and a magnitude—and all of these would need to be fairly specific, with enough advance notice to be worthwhile.
For example, if I predict that California will have an earthquake in 2023, that would certainly come true, but it’s not useful because California has many small earthquakes every day. Or imagine I predict a magnitude 8 or greater earthquake will strike in the Pacific Northwest. That is almost certainly true but doesn’t specify when, so it’s not helpful new information.
Earthquakes happen because the slow and steady motions of tectonic plates cause stresses to build up along faults in the Earth’s crust. Faults are not really lines, but planes extending down miles into the ground. Friction due to the enormous pressure from the weight of all the overlying rock holds these cracks together.
An earthquake starts in some small spot on the fault where the stress overcomes the friction. The two sides slip past each other, with the rupture spreading out at a mile or two per second. The grinding of the two sides against each other on the fault plane sends out waves of motion of the rock in every direction. Like the ripples in a pond after you drop in a stone, it’s those waves that make the ground shake and cause damage.
Most earthquakes strike without warning because the faults are stuck—locked up and stationary despite the strain of the moving plates around them, and therefore silent until that rupture begins. Seismologists have not yet found any reliable signal to measure before that initial break.
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The USGS (United States Geological Survey) also offers an answer to the same question – Can you predict earthquakes?
Can you predict earthquakes?
Here is their answer:
No. Neither the USGS nor any other scientists have ever predicted a major earthquake. We do not know how, and we do not expect to know how any time in the foreseeable future. USGS scientists can only calculate the probability that a significant earthquake will occur (shown on our hazard mapping) in a specific area within a certain number of years.
An earthquake prediction must define 3 elements: 1) the date and time, 2) the location, and 3) the magnitude.
Yes, some people say they can predict earthquakes, but here are the reasons why their statements are false:
- They are not based on scientific evidence, and earthquakes are part of a scientific process. For example, earthquakes have nothing to do with clouds, bodily aches and pains, or slugs.
- They do not define all three of the elements required for a prediction.
- Their predictions are so general that there will always be an earthquake that fits; such as, (a) There will be a M4 earthquake somewhere in the U.S. in the next 30 days. (b) There will be a M2 earthquake on the west coast of the U.S. today.
- If an earthquake happens to occur that remotely fits their prediction, they claim success even though one or more of their predicted elements is wildly different from what actually occurred, so it is therefore a failed prediction.
Predictions (by non-scientists) usually start swirling around social media when something happens that is thought to be a precursor to an earthquake in the near future. The so-called precursor is often a swarm of small earthquakes, increasing amounts of radon in local water, unusual behavior of animals, increasing size of magnitudes in moderate size events, or a moderate-magnitude event rare enough to suggest that it might be a foreshock.
Unfortunately, most such precursors frequently occur without being followed by an earthquake, so a real prediction is not possible. Instead, if there is a scientific basis, a forecast might be made in probabilistic terms.
An earthquake forecast was made in China several decades ago based on small earthquakes and unusual animal activity. Many people chose to sleep outside of their homes and thus were spared when the main earthquake indeed occurred and caused widespread destruction. However, this type of seismic activity is rarely followed by a large earthquake and, unfortunately, most earthquakes have no precursory events whatsoever. The next large earthquake in China had no precursors and thousands of people died.
The USGS focuses its efforts on the long-term mitigation of earthquake hazards and by helping to improve the safety of structures, rather than by trying to accomplish short-term predictions. /// nCa, 28 February 2023