Cyclic loading of marble: Correlating the attenuation of the electric and acoustic activities and highlighting criticality indices in terms of natural time

• Acoustic and electric activities in marble under cyclic loading are linearly correlated, indicating common underlying damage mechanisms. • Kaiser's effect, traditionally observed in acoustic emissions, also governs the electric activity (pressure stimulated currents). • A simple criterion based on the average rate of change of normalized cumulative counts in natural time reliably predicts the onset of critical fracture stage. • Predictions from the simple criterion align closely with those from variance and entropy-based criteria in natural time domain.