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Ultralow-angle faults produce giant earthquakes
Satoshi Ide1, Mikito Furuichi2, Dye S K Sato3
1Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan.
Science Advances
|July 1, 2026
Summary
Giant earthquakes are more likely on ultralow-angle faults in subduction zones. Earthquake size correlates with fault dip and alignment with the regional stress field, aiding megaearthquake forecasting.
Area of Science:
- Geophysics
- Seismology
- Tectonics
Background:
- Giant earthquakes are a significant seismic hazard.
- Understanding controls on earthquake size is crucial for hazard assessment.
- Subduction zones are sites of major seismic events.
Purpose of the Study:
- To investigate the relationship between earthquake size and fault geometry.
- To identify factors controlling the occurrence of giant earthquakes in subduction zones.
- To improve forecasting of megaearthquakes.
Main Methods:
- Analysis of global earthquake statistics.
- Examination of fault dip and earthquake size correlation.
- Case studies of fault geometry and regional stress field alignment.
Main Results:
- A simple relationship exists between earthquake size and fault dip.
- The probability of extreme earthquake events peaks on ultralow-angle faults.
- Earthquakes grow larger when fault geometry aligns with the regional stress field.
Conclusions:
- Fault dip and its alignment with the stress field are key factors controlling giant earthquake occurrence.
- Understanding stress configurations in subduction zones is critical.
- Monitoring temporal stress evolution can improve megaearthquake forecasting.
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