Will we ever be able to predict earthquakes?

 The unfolding tragedy amid the crumpled buildings of south-east Turkey and northern Syria highlights how unexpectedly earthquakes can strike. Scientists are searching for ways to spot the early warning signs of these most unpredictable of natural disasters.

They hit suddenly and without warning. The two devastating earthquakes that struck south-eastern Turkey and northern Syria have claimed thousands of lives and left many more injured or without shelter. Occurring in the early hours of 6 February, most of the victims would have been inside sleeping when the first 7.8 magnitude earthquake brought their homes crashing down on top of them. 

The first indication semiologists had that a major disaster was unfolding were the abrupt flashes of activity on their sensitive instruments spread throughout the world as the seismic waves produced by the first earthquake reverberated around the globe. A few hours later this was followed by a second large earthquake of 7.5 magnitude.

The relative shallowness of both quakes meant the intensity of the shaking was particularly severe. And as the area continues to shudder with aftershocks, experts at the United States Geological Survey have warned that those who survived, and the rescue workers now flocking to the region to help, face significant risks from landslides and ground liquefication as a result of the shaking. 

But as the world races to provide aid to the shattered communities on either side of the border between Turkey and Syria, some are wondering why we didn't see this coming.

The East Anatolian fault system where the earthquakes occurred is part of a tectonic "triple junction" where three tectonic plates – the Anatolia, Arabia and Africa plates – grind against each other. Since 1970, only three earthquakes of magnitude 6 or larger have hit the region, and many geologists believed the region was "overdue" for a large earthquake.

In truth, the science of predicting earthquakes is very, very difficult. While there are often minute signals that can be detected in the seismic data after an event has happened, knowing what to look for and using that to make forecasts beforehand is far more challenging.

"When we simulate earthquakes in the laboratory we can see all these little failures happening – there is some cracking and some flaws that appear first," says Chris Marone, a professor of geosciences at Sapienza University of Rome, in Italy, and Penn State University in Pennsylvania, US. "But out in nature there is a lot of uncertainty about why we often don't see foreshocks or indications that there is going to be a big earthquake."

Geologists have been trying to use modern scientific methods to predict earthquakes since at least the 1960s, but with little success. Much of the reason for this, says Marone, is the complexity of the fault systems that criss-cross the globe. There is also a lot of seismic noise – the Earth is constantly grumbling and rumbling away, which, when combined with the anthropogenic clatter of traffic, building work and daily life, makes it hard to pick out clear signals. 

According to the United States Geological Survey, it takes three things to produce a really useful earthquake prediction – the location where it will happen, when it will happen and how big the event will be. So far, they say, no one can do that with any certainty. 

Instead geologists produce what are their best guesses in "hazard maps" where they calculate the probability of an earthquake within a timeframe of several years. While these can help with some degree of planning, such as improving building standards in the areas most at risk, it doesn't provide the level of prediction needed to provide early warnings to the public to allow them to evacuate or take shelter. And not everyone who lives in an earthquake zone can afford the kind of infrastructure needed to withstand large amounts of shaking . 

"In Turkey and Syria, there were a lot of factors that meant buildings were in a state where they were ready to pancake and fail," says Marone. "In a lot of the Western world there have been seismic reinforcement codes that were implemented in the 1970s and 1980s. But it costs a lot to build and retrofit buildings." (Read about how Japan's skyscrapers are built to survive earthquakes.)

So, scientists have instead been searching for ways to make earthquake predictions more accurate. Alongside seismic signals, researchers have searched for clues in a wide variety of places – from the behaviour of animals to electrical disturbances in the Earth's upper atmosphere.

Recently, however, there has been growing excitement around the capabilities of artificial intelligence to detect the kind of subtle signals that humans miss. Machine-learning algorithms can analyse vast amounts of data from past earthquakes to look for patterns that might be used to predict future events.

"This kind of machine-learning-based prediction has produced a lot of interest," says Marone. He and his colleagues have for the past five years been developing algorithms that are capable of detecting failures in simulated earthquake faults in the laboratory. Using fist-sized blocks of granite, they can recreate the stress build up and friction that might occur at a fault, building up pressure until the fault slips, creating what they call "labquakes".

"Elastic waves travel through the fault as it breaks little by little," says Marone. "We can predict when the failure is going to occur in the laboratory based on these changes in elastic properties and the noise coming from foreshocks in the fault zone itself. We'd love to port this to the Earth, but we are not there yet."

Transferring this predictive power of AI to the larger, complex environment of real-world fault zones is far more challenging.

Scientists in China have been looking for ripples in electrically charged particles in the Earth's ionosphere in the days leading up to earthquakes

"There are a few cases where people have figured out how to do it in post-prediction after an earthquake which suggest this might work," says Marone. "But there's not been a big breakthrough yet."

Scientists in China, for example, have been looking for ripples in electrically charged particles in the Earth's ionosphere in the days leading up to earthquakes caused by changes in the magnetic field above fault zones. One group led by Jing Liu at the Institute of Earthquake Forecasting in Beijing, for example, said it could see disturbances in the atmospheric electrons above the epicentre of the earthquake that hit Baja, California, 10 days before it hit in early April 2010.