On 1 January 2024, a devastating magnitude-7.6 earthquake struck the Noto Peninsula in Japan. The earthquake caused severe shaking, a tsunami and landslides, which killed almost 300 people and damaged over 46,000 homes. It was the deadliest earthquake in Japan since the Great East Japan Earthquake in 2011. 

Earthquakes are generally caused by abrupt, rapid movements of pieces of the Earth’s crust along fractures known as faults. Researchers working with Assoc Prof Wei Shengji of NTU’s Asian School of the Environment and Earth Observatory of Singapore showed that the Noto earthquake started unexpectedly in a zone that was thought to have limited capability of initiating a powerful earthquake.

From their analysis of satellite and seismic sensor data, the scientists discovered that the earthquake started from an unusually slow movement along a fault. The slow movement was likely due to fluids in the fault and the heterogenous composition of the faults.

This type of earthquake presents a challenge for current earthquake early warning systems, which are less likely to pick up signals from the slow movement to trigger alerts for large earthquakes.

The findings contribute to an in-depth understanding of how earthquakes occur and highlight the importance of analysing multiple datasets to estimate seismic hazards. The research may also aid the development of more accurate tools for seismic and tsunami hazard assessment.