LONDON – A powerful aftershock hit southern Turkey on Monday, in what has been a string of tremors to hit the region since the devastating 7.8 magnitude earthquake earlier this month.
The death tolls for both Turkey and Syria have risen steadily since February 6, with the death toll now exceeding 50,000. According to statistics from the UN refugee agency, UNHCR, 15 million people in 10 different provinces in Turkey have been affected by the major earthquakes and subsequent tremors.
Over the course of three weeks, Turkey has experienced several earthquakes with a magnitude of 5.6 or higher. To understand the continuing tragedies there, Yahoo News spoke with Ebru Bozdag, an associate professor of geophysics at the Colorado School of Mines.
How does an earthquake happen?
“The primary cause of earthquakes is the relative movement of tectonic plates on the surface,” Bozdag said.
“The Earth has, roughly speaking, four main layers. From surface to center: crust, mantle, outer and inner cores. The crust breaks up into rigid tectonic plates, which float on top of the mantle due to the convection currents in the mantle. When the plates move in relative to each other, earthquakes occur at plate boundaries, but we also observe some seismic activity within tectonic plates as well.
“Another cause of earthquakes is related to mantle plumes and associated volcanic activity that can occur inside tectonic plates,” she explained, “such as the type of earthquakes seen in Hawaii, which is located almost in the middle of the Pacific plate.”
Why has Turkey experienced so many earthquakes this month?
“Turkey is located in one of the most seismically active regions on Earth,” Bozdag said. “Due to the northward thrust of the Arabian plate and the subduction (when one plate moves under another and into the mantle) in the Mediterranean, the Anatolian plate is trying to escape westward, performing a counter-clockwise rotational movement using the two major faults zones: North Anatolian and East Anatolian faults.”
She continued: “The recent earthquakes in East Anatolia have occurred on the East Anatolian fault and the nearby faults where three tectonic plates meet, what is called a triple junction: the Arabian plate, the Anatolian plate and the African plate. The Arabian and African plates are moving north by about a few millimeters each year, accumulating stress at the plate boundaries, known as fault zones. We observe the stress release along the faults with the recent earthquakes.”
Is it possible that Turkey may continue to experience more earthquakes in the coming weeks or months?
“Yes, after large earthquakes it is common to have aftershocks for a few months, sometimes more than a year, until the tectonic plates settle down,” Bozdag explained.
“It is also possible that earthquakes could increase strain on the continuation of the faults or nearby faults, which could trigger other earthquakes.”
Does climate change affect seismic activity?
“We do not have such an observation, but probably not, since the primary source of seismic activity is generated by internal processes,” Bozdag said.
Could the earthquakes lead to further catastrophic natural disasters in the region?
“After such large earthquakes, we observe aftershocks that gradually decrease,” Bozdag said. “Then a certain amount of time is needed to accumulate the same amount of stress to generate similar earthquakes in the region. So it is unlikely to have large earthquakes in the same places now.
“But,” she said, “disaster is directly related to the quality of the buildings. If the region is well prepared, follows the rules and gets feedback from science and engineering experts, the next big earthquake doesn’t have to be catastrophic.”
Was the original earthquake predicted to happen? If so, were people warned?
“We can’t predict earthquakes, which means we can’t say that an earthquake will happen in this place, at this time, with this magnitude,” she said. “But we know quite a bit about the faults and monitor the seismic activity regularly, so we know where to expect earthquakes and their associated strengths reasonably well.”
How can Turkey plan for further earthquakes to prevent fewer deaths and destruction?
“Turkey has the scientific and technical background to monitor seismic activity and determine seismic hazards,” Bozdag explained. “Turkey also has the right building codes. The problem occurs with the execution of these codes. To reduce seismic hazards, we must build appropriate buildings in appropriate locations, and take the seismic risk into account.
“Naturally it would be better to build cities on hard rocks rather than on soft sediments where such areas should be used for agriculture or recreational areas etc,” she said. “It is also desirable not to build buildings on fault lines. Unfortunately, the quality of buildings is the main problem in Turkey, which is made worse because they are built on soft materials such as sedimentary basins, which amplifies the intensity.”