The Levant Fault System : A New Approach for Improved Seismic Risk Assessment

Thanks to the SHERIFS algorithm, the energy accumulated within the fault system is redistributed across all physically possible ruptures, making it possible to simulate earthquakes involving multiple connected segments. This method shows that seismic hazard is not uniform : some secondary fault branches may present danger levels as high as those of major faults.

The researchers tested several scenarios, including maximum magnitudes up to 7.9, and assessed how fault slip rates translate into earthquakes. The final model, based on a fully interconnected fault system, indicates that only 5% of the total energy is released aseismically (not as earthquakes), which is consistent with field observations.

By combining this model with ground-motion simulations, the resulting hazard maps show that for a 475-year return period, peak ground accelerations exceed 0.2 g across all of Lebanon and reach 0.3 g within 20 km of the faults. For short-period shaking (0.2 s), spectral accelerations exceed 0.6 g and rise to as much as 1 g along the most active faults.

This study highlights the importance of accounting for complex fault interactions to better anticipate seismic hazards and to support the development of building standards adapted to earthquake risk.