Large earthquakes are always a surprise — and always inevitable. Monday’s deadly events in Turkey and Syria are no different. The fault system that caused them and the region’s seismicity are well documented from painstaking field studies, historical records and geophysical observations over many decades. Yet no seismologist could have predicted the exact location, time and magnitude of this week’s quakes.
That said, the past is a good guide to what to do now. Lessons learned from previous earthquakes can now be applied in the region. And this disaster can serve as a warning to be ready for earthquakes to come.
To understand how, consider the tectonics. The Arabian plate is on an inexorable march northward and, as a result, the region caught between it and the Eurasian plate — Turkey — has fractured into pieces.
The surfaces that slipped on Monday lie close to the Arabian plate and are part of the constantly active East Anatolian fault, which works alongside the North Anatolian fault. As the Arabian plate moves north, western Turkey squeezes out of the way of the collision zone.
Although incremental plate movements are easy to see using satellite measurements, the earthquakes they produce are notoriously irregular. Some faults remain quiescent for more than a thousand years. When intervals between large earthquakes are long, as is the case with many of Earth’s most dangerous faults, people are often unaware of the hazard and unprepared. Even geologists can be caught flat-footed, as I learned in 2008 when a magnitude 7.9 earthquake hit Sichuan, China, which I was studying. Many thought the region to be deforming too slowly to trigger such a damaging event.
So, what does all this mean for the nations reeling right now?
First, experience has taught us that some fault systems produce cascades of earthquakes over periods of days to decades. Continuing to prepare for further large quakes in Turkey and Syria is just as important as rescuing and rebuilding from this one. The historical seismicity on the East Anatolian fault is not so different from the activity on the North Anatolian fault that preceded a half dozen large earthquakes from 1939 to 1967.
Second, it will likely take years to appreciate the extent of this disaster. Early reports of damage and fatalities generally focus on cities. In some earthquakes, the impact is never precisely known. For example, estimates for death toll of the earthquake that hit Haiti in 2010 range from less than 100,000 to more than 300,000. Even following reconstruction, the impacts on individuals — who might have lost their homes, livelihoods and families — can last a lifetime. A true understanding of the physical and social effects of a large earthquake will emerge only over decades.
Third, aid should focus on the priorities of local people and long-term resilience. Rebuilding homes to poor engineering standards will solve the immediate need for shelter, but will place people at risk of continued seismic activity.
The fourth lesson from the past is that while earthquakes bring untold suffering, they can also usher in positive change. The 2004 Sumatra earthquake helped end a civil war as both parties came together to focus on recovery. The state of Aceh in northern Sumatra remains peaceful. Opportunities to improve infrastructure and resolve political disagreements must be seized in Turkey and Syria, given the preexisting humanitarian crisis along the border.
Finally, Americans watching news of Turkey and Syria’s tragedy know this: People could wake up any day to a similar magnitude earthquake in San Francisco. Like the North and East Anatolian faults, the San Andreas is a long, shallow strike-slip fault, with a comparable slip rate.
There has not been a maximum magnitude earthquake on most of the United States’ dangerous active faults in living memory. That includes the Cascadia in the Pacific Northwest, the Wasatch in Utah and many more. The United States, like every seismically active nation, would be wise to use periods of quiescence to mitigate the effects of unpredictable but inevitable earthquakes.
Judith Hubbard is a visiting assistant professor of earth and atmospheric sciences at Cornell University.