## 3 Results and Discussion
### Overall Interpretations of the Results of Baseline Case
Therefore, if the monitoring position is close to the slope, it may also help identify different wave erosion forces. The amplitude of seismic signals undergoes significant changes at 1188 s-1218 s, 2528 s-2562 s, and throughout Stage 3. These changes are primarily attributed to slides and the impact of waves. A detailed explanation of how these events influence the seismic signals is provided in Sections 3.2 and 3.3. The amplitudes of seismic signals from Acc 1, as shown in Figure 5b, were cut off during Stage 3 because the accelerometer was exposed on the slope and can no longer accurately measure the seismicity of the slope. Figure 5e shows the acoustic signal from the microphone. During Stage 1 and Stage 2, the amplitude of the acoustic pressure mostly oscillates steadily, as the wave action involves less wave breaking and splashing and more swashing. In Stage 3, however, the amplitude of the acoustic signal is amplified due to the increase in wave height and H\({}_{\text{w}}\). The increase in wave height and H\({}_{\text{w}}\) expands the erosion area and changes the type of wave erosion from swash to impact. These changes lead to more frequent wave breaking and splashing, amplifying the sounds during erosion. This suggests that increases in wave height and H\({}_{\text{w}}\) may result in louder sounds due to wave breaking and splashing, which produces a more pronounced acoustic signal. Figure 5f-i present the pore pressures at PP1 to PP4. From these figures, the pore pressure remains stable with a constant amplitude envelope during Stage 1 and Stage 2. However, in Stage 3, the pore pressure undergoes significant changes due to the increase in H\({}_{\text{w}}\) and wave height. Wave resonance might have occurred during Stage 3 due to changes in the profile of the slope, further increasing the wave height. For Stage 3, the water level WL1, pore pressure PP1-PP4, and run-up height of wave H\({}_{\rm w}\) (Figure 6) were compared, as well as the deformed profiles of the slope in Figure 7, to discuss the reasons for the pore pressure changes. Figure 6 marks the timing (t\({}_{0}\)-t\({}_{6}\)) for which pore pressure changes corresponded to changes in H\({}_{\rm w}\) and wave height. Figure 7 shows the change in the slope profile during t\({}_{0}\)-t\({}_{6}\), with the slope profile made through video screenshots and manually tracing. Figure 6: (**a**) Wave water level, WL1; (**b**–**e**) pore pressure (PP1–PP4); (**f**) run-up height of wave during Stage 3 (3800 s\(\sim\)5250 s). (The arrows show the tread of the data. The black dots represent “Hw” data measured from test video snapshots, and they connected by the black dashed line.) Figure 6a,b show that the water level and pore pressure PP1 follow a similar envelope curve from t\({}_{0}\) to t\({}_{3}\). In these figures, the amplitude of the water level and pore pressure PP1 increase at t\({}_{1}\), followed by a decrease from t\({}_{2}\) to t\({}_{3}\). As the piezometer PP1 was installed near the slope surface (as indicated in Figures 2 and 7), the measurement of pore pressure was directly affected by changes in the water level above it. This indicates that the changes in pore pressure near the slope closely reflect the changes in water level amplitude. The distances between the piezometers PP1-4 and the slope surface gradually shorten as the slope is eroded (Figure 7). This causes the amplitude of the pore pressure PP1-4 to increase from t\({}_{1}\) to t\({}_{2}\) (Figure 6b-e). As the distance between the piezometers and the slope surface decreases, the influence of the waves on the pore pressure increases, leading to an increase in the amplitude of the pore pressure. Variations in the pore pressure PP2-4 and H\({}_{\rm w}\) show similar trends, as indicated by the red arrows in Figure 6c-f. Both increase from t\({}_{0}\) to t\({}_{3}\), then decrease from t\({}_{3}\) to t\({}_{4}\) and from t\({}_{5}\) to t\({}_{6}\).