## 4 Results and Discussion
### The Requirement for the Single-Station Inversion  
In general most waveform inversion methods are limited by the quality of the seismic data and the station coverage. The results of waveform inversion will be more robust if seismic records having high SNR values are used and station coverage is complete. It was particularly noteworthy that PFH inversion could be executed with high-quality seismic records from a single station. Accordingly, single-station waveform inversions were performed on each of the 15 station records. The residual of the M\({}_{\text{LQ}}\) value between the multistation inversion and the single-station inversion was calculated to testify to the quality of the single-station inversion (Table 4). The M\({}_{\text{LQ}}\) value was defined as the value of the landslide mass multiplied by the runout distance [17]. The results revealed that half of the single-station inversions had residuals below 0.2 and had fine consistency with the multistation inversion. It appeared that the seismic records having higher SNR values led to lower residuals and were more suitable for use in single-station inversion. The M\({}_{\text{LQ}}\) value of the TWKB single-station inversion was overestimated and led to a high residual, which might have been caused by the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Stage** & **Duration (s)** & **Runout Distance (m)** & **Average Velocity (m/s)** \\ \hline
**1** & 37 & 1200 & 32.5 \\
**2** & 17 & 500 & 29.4 \\
**3** & 120 & 900 & 7.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Three dynamic process stages of the Taimali landslide environmental conditions of the seismometer or geological factors. The seismic amplitudes recorded by the TWKB station were abnormally high and unsuitable for single-station waveform inversion. Although the YHNB station had a high SNR value, the M\({}_{\text{LQ}}\) value of the YHNB single-station inversion was underestimated, possibly due to its distance from the seismic source and to waveform attenuation. The rest of the high residuals of M\({}_{\text{LQ}}\) occurred at the stations having low SNR values. In addition, the single-station inverted force can be applied to synthesize waveforms for other stations to acquire high correlation coefficients, which enhances the reliability of the single-station inversion (Figure 8). The residuals between 15-station inversion and single-station inversion reveal that the errors caused by single-station inversion increase with station distance to the landslide (Figure 9). Once the residuals are considered as the errors, the MASB single-station inversion would cause an error of 5%, and result in a slight decrease of 0.1-0.15 in the correlation coefficients between the synthetic and observed waveforms. As the error caused by the single-station inversion is larger than 20% (e.g., YHNB, KMNB, etc. ), the correlation coefficient between the synthetic and observed waveforms would decrease significantly to lower than 0.3. The noise level at each station is another factor to influence the waveform inversion. In Figure 9, we can observe that when the number of components with SNR > 8.5 is less than two, the errors of single-station inversion are larger than 20%. Moreover, the azimuthal coverage of the seismic network is not very dense; the azimuth gap is large especially in the east, which will influence the selection of seismic records. Therefore, we deduce that the quality of the seismic data and the station coverage are the main factors in determining the results of waveform