New Year's Day earthquake that hit Noto in Japan had TWO epicentres

Japan's Noto Peninsula was hit by a massive earthquake on New Year's Day 2024. The 7.5 magnitude quake shook the region and killed more than 280 people, damaging more than 83,000 homes. A surprising new discovery has been made about this event.

Geologists have found that the earthquake started almost simultaneously at two different points on the faultline. This led the seismic rupture to encircle and break through the barrier, a resistant area on the fault. Intense pressure was applied from both sides of the barrier due to this rare "dual-initiation" mechanism, following which a powerful burst of energy was released. The Noto Peninsula shook intensely because of this reason.

Several intense seismic swarms were recorded before the bigger earthquake. They are known to trigger catastrophic tremors and so the scientists analysed the geospatial data and recordings of seismic waves within the Earth during this swarm.

An international team of researchers from the United States, France, China and Japan tried to understand the connection between the swarm of smaller tremors and the larger earthquake and identified a previously unknown barrier in the region of the swarm.

The study on 2024 Noto earthquake

Led by Lingsen Meng, a UCLA associate professor of earth, planetary and space sciences, UCLA graduate student Liuwei Xu and UC Santa Barbara geophysics professor Chen Ji, the team found that the earthquake began almost simultaneously in two separate locations on the fault.

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"The earthquake started in two places and circled together," Meng said.

"The first one started waves that travelled fast and triggered a different epicentre. Then both parts propagated outward together and met in the middle, where the barrier was, and broke it."

Scientists are surprised to witness the dual initiation process happen in reality since it has mostly only been seen in simulations. Two epicentres mean that the quake poses a higher risk for stronger shaking and more damage.

"We were able to observe it because Japan has very good seismic monitoring stations and we also used GPS and satellite radar data. We grabbed all the data we could find! It's only through all of this data together that we got really good resolution on this fault and could get into these fine details," Meng said.

The team also thinks that several quakes lack such data, so it is possible that such earthquakes are much more common.

The study has beenpublishedin the journalScience.