Zee Media Bureau
New Delhi: In a major development, scientists recently discovered that slow-slips events or slow- motion earthquakes can lead to tsunami-generating regular earthquakes.
For the first time ever an international team of scientists from US, Japan and New Zealand detected slow-motion earthquakes off the coast of Gisborne coast in New Zealand that can trigger tsunami.
This research highlights that these slow-slips events can rupture the shallow portion of a fault that also moves in large tsunami-generating earthquakes.
Slow-slip events are geological forces similar to earthquakes but much lesser in intensity. They do not release the whole strain in seconds but do it over days to weeks, creating quiet, centimeter-sized shifts in the landscape.
"Our results clearly show that shallow, slow-slip event source areas are also capable of hosting seismic rupture and generating tsunamis," said study co-author Yoshihiro Ito, professor at Kyoto University in Japan.
The study, published in the journal Science, was undertaken at the Hikurangi subduction zone, where the Pacific Plate subducts beneath New Zealand's North Island.
The slow-slip event lasted two weeks, resulting in 15-20 centimeters of movement along the fault that lies between New Zealand and the Pacific Plate, a distance equivalent to three to four years of background plate motion.
If the movement had occurred suddenly, rather than slowly, it would have resulted in a magnitude 6.8 earthquake.
The slow-slip event that the team studied occurred in the same location as a magnitude 7.2 earthquake in 1947 that generated a large
tsunami.
The finding increases the understanding of the relationship between slow-slip and normal earthquakes by showing that the two types of seismic events can occur on the same part of a plate boundary.
In a few cases, these small shifts have been associated with setting off destructive earthquakes, such as the magnitude 9.0 Tohoku-Oki earthquake that occurred off the coast of Japan in 2011 and generated a tsunami that caused the Fukushima Daiichi nuclear power plant disaster.
(With IANS inputs)
