The High-Frequency Signature of Slow and Fast Laboratory Earthquakes

Area of Science:

• Geophysics
• Seismology
• Earthquake Science

Background:

• Tectonic faults exhibit diverse slip behaviors, from slow aseismic creep to rapid earthquake rupture.
• Understanding seismic radiation from these varied slip modes is crucial for earthquake hazard assessment.

Purpose of the Study:

• To document the seismic radiation properties of slow and fast laboratory earthquakes.
• To investigate the relationship between slip modes and emitted high-frequency energy.

Main Methods:

• Laboratory friction experiments using ultrasonic sensors to record acoustic emissions at 5 MHz.
• Controlled variation of normal stress and loading stiffness to produce a spectrum of slip modes.

Main Results:

• A full continuum of slip modes, including slow events, radiate measurable high-frequency energy (100-500 kHz).
• Peak amplitude of high-frequency signals scales directly with fault slip velocity.
• High-frequency energy originates from changes in slip rate, shear strain, and contact junction breakdown.

Conclusions:

• Fault slip rate is a fundamental control on high-frequency seismic radiation across all slip modes.
• Close-proximity measurements to fault zones are vital for characterizing seismic radiation.
• Findings enhance understanding of earthquake physics and hazard assessment.