Causes of the 2011 Mega-Earthquake in Japan Revealed

On January 9, seismologists announced they had found clues to why the 2011 mega-earthquake struck Japan, stemming from an initially seemingly harmless fault line.

The findings have raised concerns about Japan's earthquake response strategy, as well as for other locations, including the well-known San Andreas Fault in California, USA, which has a similar geological profile, according to the scientists.

Geologists Hiroyuki Noda of the Japan Institute of Geosciences and Marine Technology, and Bran and Nadia Lapusta of the California Institute of Technology used computer models to analyze and publish their findings on the devastating earthquake of March 11, 2011, which led to a tsunami that killed 19,000 people, caused widespread devastation, and triggered the Fukushima Daiichi nuclear disaster.

The 9.0 magnitude earthquake occurred off the coast of northeastern Japan in an area known as the Japan Trench, where the Pacific tectonic plate subducts beneath the Okhotsk plate, and the Japanese peninsula lies right at the point of contact.

The earthquake's epicenter was located about 200 km east of Sendai, Honshu Island. Previously, the Japan Trench was considered relatively stable and only exhibited "gradual faulting," meaning that the movements of tectonic plates were slow and without significant sudden disturbances.

According to the widely accepted seismic theory, these faults do not cause mega-earthquakes, like the slow expulsion of hot gases from a steam engine. But Noda and Lapusta argue that the previously thought-to-be-long and slow-moving fault may have weakened abruptly due to a nearby geological upheaval.

If this upheaval originated from the eruption of hot lava under the ocean, a major earthquake could occur. “Our research shows that what are thought to be gradual geological upheavals can still cause large earthquakes, amplified in intensity and destructiveness,” Noda said.

The authors say they hope their work will be useful for future earthquake forecasting and response efforts. Some experts also argue that Japan's current earthquake preparedness program is too focused on the risks to the Tokyo area, which is located quite far south of the 2011 earthquake.

The findings also point to risks at the San Andreas Fault off the coast of California, according to research published in the scientific journal Nature.

According to (Vietnam+) - VT