# Towards Automatic Landslide-Quake Identification Using a Random Forest Classifier
## 4 Application to Seismic Records of Typhoon Periods  
### Typhoon Morakot in 2009  
To test the applicability of the present classifier, seismic data collected during Typhoon Morakot on 7-10 August 2009 were adopted. First, manual classification was conducted in accordance with \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**For Landslide-Quake**} & \multicolumn{2}{c}{**For Earthquake**} & \multirow{2}{*}{**Accuracy (\%)**} \\ \cline{2-2} \cline{5-6}  & **Sensitivity (\%)** & **Precision (\%)** & **Sensitivity (\%)** & **Precision (\%)** & \\ \hline oMA classifier & 50.5 & 50.9 & 53.7 & 54.3 & 65.6 \\ LF1 classifier & 46.3 & 47.8 & 45.3 & 54.8 & 53.9 \\ TD classifier & 80.4 & 83.5 & 84.6 & 82.6 & 87.7 \\ FD classifier & 74.3 & 80.3 & 85.5 & 85.1 & 84.7 \\ TD-FD classifier & 86.9 & 89.0 & 88.8 & 88.4 & 91.3 \\
2009 TP Morakot & 98.9 & 73.7 & 44.2 & 59.0 & 95.6 \\
2015 TP Sudeler & 100 & 10.0 & 52.9 & 32.5 & 90.2 \\ \hline \hline \end{tabular} Note: TD represents time domain, FD represents frequency domain, TP represents typhoon.  
\end{table} 
Table 4: Performance of the classifiers created with different sets of features and validation to two typhoons. the earthquake catalog of Taiwan's CWB to construct a seismic event catalog. The four days of data contained 193 landslide events and 52 earthquake events. In addition, 67 landslide events were measured and identified by at least three seismic stations; 30 landslide events, by two seismic stations; and the remaining 96 landslide events, by single stations. The seismic data during Typhoon Morakot were automatically classified by the TD-FD classifier, and the results had accuracy of 87.3%, as shown in Table 4. Of a total of 193 landslide events, the TD-FD classifier correctly interpreted 191 landslide events and failed on two events: one was misidentified as an earthquake event, and the other was not detected. The sensitivity for landslides was 98.9%. Of 52 earthquake events, the classifier correctly identified 23 earthquake events and misclassified 29 as landslide events. The sensitivity for earthquake cases was 44.2%. Of a total of 220 records classified as landslide events, 191 were actually landslide cases, and the other 29 were earthquake cases in fact. The precision for landslides was 86.8%. Of 24 records classified as earthquake events, 23 were actually earthquake cases and the remaining one was a landslide case. The precision for earthquakes was 95.8%. It was concluded that the present automatic classifier had a higher possibility of misclassifying an earthquake as a landslide than of misclassifying a landslide as an earthquake. Figure 10a is an example of a correct classification of a landslide event. The features of a landslide case are obvious in both the waveform and the spectrogram, and the signal of the feature is over 20 s in length. Figure 10b is a successful classification of an earthquake event. The characteristics of an earthquake can be observed clearly in the waveform and in the frequency. Figure 10: (**a**) A signal classified correctly as a landslide-quake; (**b**) a signal classified correctly as an earthquake; (**c**) a landslide-quake signal classified as noise; (**d**) an earthquake signal classified as a landslide-quake. Figure 10c is a landslide event which was not detected by the present classifier due to the features of the landslide being discoverable only by visual detection. Some ambiguous patterns resembling landslide signals can be seen in the waveform and the spectrogram. However, it could not be recognized by the present classifier because of the short duration and small amplitude. The signal-to-noise ratio of this record is 6.54, which is comparable to the normal values of 4-4.5, indicating the very close vibration magnitudes of this record and a noisy signal. The attributes of this record are similar to the features of a noise case, and the classifier was unable to discriminate it from a noise event. Figure 10d is an example of misclassifying an earthquake as a landslide.