Diking is one culprit behind strong earthquakes, a team of researchers has warned.
While diking is fairly known to scientists, this is the first link made between the geologic event and quakes that are 6 or 7 in magnitude.
Diking occurs when the tectonic plates of Earth move apart, causing the magma beneath the planet’s surface to rise and form vertical intrusions called dikes. Dikes push on surrounding rocks and create strain.
The team led by Christelle Wauthier, a geoscientist from Penn State, probed the links between two natural occurrences in Congo, East African Rift System, back in 2002.
The Jan. 17, 2002 eruption of Nyiragongo volcano – which killed more than 100 people and left more than 100,000 homeless – was followed by a magnitude-6.2 quake in Kalehe, 12 miles away from the volcano, eight months later.
Using remote sensing, the team measured changes to Earth’s surface prior to and after the two disastrous events.
“[W]e found that the most likely explanation, or best-fitting model, was a 12-mile diking intrusion in between Nyiragongo and Kalehe," reported Wauthier, referring to the deformation detected in January 2002.
They used the same method for the magnitude-6.2 earthquake in October of the same year, finding one fault on the East African Rift System border that slipped and triggered the quake.
After conducting the Coulomb stress-change analysis, the researchers said that the January dike could have incited the October earthquake.
This analysis – typically used for seeing if a quake in a given region will trigger a secondary quake close by – calculates stress changes from a deformation at potential receiver faults in a region. Positive changes mean the source is taking a receiver fault closer to slippage and the generation of an earthquake.
The team proposed in this specific case that the opening of the dike did push outward against nearby rocks, which strained and transferred stress to adjacent rocks. The fault went closer to failure, with the strong quake triggered after eight months.
The findings were published in the journal Geochemistry, Geophysics, Geosystems.
A powerful magnitude-6.4 earthquake shook southern Taiwan Saturday morning, leaving more than three dozen dead and hundreds injured. The city of Tainan sustained the most destruction and is at the center of continuing rescue efforts.
The quake struck as preparations for Lunar New Year Celebration – one of the country’s biggest holidays – were underway.