Off-fault damage controls near-surface rupture behaviour in soft sediments

Area of Science:

• Geophysics
• Earthquake Science
• Fault Mechanics

Background:

• Surface-rupturing faults pose significant earthquake hazards.
• Near-surface rupture behavior and energy dissipation are poorly understood.
• Limited data exists on off-fault energy dissipation around rupture tips.

Purpose of the Study:

• To investigate the role of off-fault energy dissipation in shallow seismic fault behavior.
• To quantify the energy dissipated by off-fault damage in near-surface fault regions.
• To explain observed slow rupture velocities and low radiation efficiencies in shallow earthquakes.

Main Methods:

• Integration of experimental results with field measurements from Dead Sea seismic faults.
• Estimation of off-fault damage energy as a percentage of total fracture energy.
• Analytical modeling to assess the impact of fracture energy on rupture propagation.

Main Results:

• Off-fault damage accounts for up to 85% of total fracture energy in M_w ≈ 6 events.
• Increased fracture energy from off-fault damage significantly slows or halts rupture propagation near the surface.
• Provides a plausible explanation for slow rupture velocities and low radiation efficiencies in shallow, soft-sediment ruptures.

Conclusions:

• Off-fault damage is a critical factor in controlling near-surface earthquake rupture dynamics.
• Understanding off-fault energy dissipation is crucial for assessing earthquake hazards.
• The findings contribute to explaining phenomena observed in shallow seismic events.