2140 To limit non-representative AE activity related to specimen relaxation and early contact effects, the algorithm ignores points below a user-defined stress threshold ignore(default ignore =5MPa). The corresponding force threshold is: }ignore =®ignore !<<< á (6) Thus only points with }≥}ignore are considered. A baseline segment of ;Ç is taken from the initial portion of the accepted data (default Ñbase = 40 rows). The baseline median is: med =median(; Ç(1. .Ñbase)) (7) The median absolute deviation (MAD) is computed as: MAD=median(∣ ; Ç(O)−med ∣))/!..4base (8) A detection threshold is then defined as: Thr =med+k ⋅ MAD (9) where kis a user parameter (default k=5). To avoid false detection under very low AE activity, an additional constraint is applied: ~(O)≥~Ä©™ (10) where ~Ä©™is a user parameter (default ~Ä©™ =5 hits per step). The Kaiser point is defined as the first data step O.satisfying all conditions: ;Ç (O)>thr ∧ (O)≥ignore ∧ ~(O)≥~Ä©™ (11) The Kaiser stress is then: . =(O.) (12) This operational definition corresponds to the first statistically significant increase of AE activity during loading, consistent with the standard Kaiser-effect concept used for stress memory in rocks. 3. RESULTS AND ANALYSIS Specimens were evaluated using three predefined quality criteria. A specimen was classified as valid only if: • a Kaiser point could be identified (σK not empty), meaning a distinct AE onset attributable to stressmemory could be determined; • the overall AE activity was sufficient (Total hits ≥ 5000) to ensure robust detection; • the Kaiser point did not occur too late relative to peak stress (σK/σpeak ≤ 0.65), so that the detected onset reflects a reproducible stress-memory threshold rather than late-stage damage close to failure.
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