# Ensemble Clustering in GPS Velocities: A Case Study of Turkey
## 3 Results and Discussion
### Comparison of Clustering Results with Ensemble Clustering  
The MCLA ensemble clustering method has yielded quite consistent results with clustering results and one can say that it improves the results by removing the subjectivity of the clustering algorithms. Figure 8 shows individual clustering and MCLA ensemble results for eastern Turkey, with the block model at [5], as black solid lines. In the tectonic sense, this is where Arabian and Eurasian plates converge and cause the extrusion of Anatolia towards the west [5]. Therefore, it is quite natural to see three different clusters at this point. Clustering algorithms are quite successful to divide GPS sites into clusters without prior information. Figure 6: Ensemble results gathered from five clustering algorithms for horizontal GPS-derived velocity field with: (**a**) HGBF; (**b**) MCLA; (**c**) NMF methods. Black solid lines are the block model at [5]. Gray thin lines show active faults [23]. Figure 7: Ensemble results gathered from five clustering algorithms for horizontal GPS-derived velocity field in velocity space: (**a**) HGBF; (**b**) MCLA; (**c**) NMF methods. The colors and the shapes are the same as the map view of the locations in the previous figure. However, clusters of some sites vary with algorithms. One can see in Figure 8, MLZ1, BING, and SIRN GPS sites are in different clusters due to varied methods. As described above (Figure 5a--Number 2), the SIRN site probably has a local effect and is assigned to a cluster that is not even close. However, BING and MLZ1 sites are varied between neighbor clusters. The MCLA ensemble method (Figure 8f) could not do much about the SIRN site (because of the local effects in this site--See Figure 1) but assigned the other sites to the Arabian plate. Figure 8f gives the result of clustering the eastern part and the green dashed line shows the border of the Eurasian and Arabian plates according to five clusters of Turkey. The boundaries of the MCLA clustering are shown with green dashed lines. Comparing our block border with [5], here we only have one border between Eurasia and Arabian plates. Our border is very close to their Caucas block border but here we do not have that many blocks. In the eastern part while they have five blocks we only have three clusters. The reader should also remember that in [5] the area of the paper is quite large, the Africa-Arabia-Eurasia continental collision zone because they have worked on continental deformation. As one can see in Figure 9, the western part of Turkey has a complex dynamic mechanism for extension in the Aegean because of the subduction and slab retreat along the Hellenic trench [5]. One can see the difference between clustering algorithms for the Aegean part GPS sites in Figure 9a-e. From north to south, AYVL, KIKA, SALH, DENI, and TVAS GPS stations are in two different clusters, the Aegean coast cluster and the Anatolian cluster, due to the varied algorithms. One can see in Figure 9d, even CAVD, CAV1, and ELMI GPS sites are in the Aegean cluster as a result of the mini batch \(k\)-means algorithm. Figure 9f shows the last decision for the western part of the Turkey cluster analysis. All these stations except CAVD, CAV1, and ELMI, decided to be in the Aegean cluster as a result of the MCLA algorithm (Figure 9f). Compared to the [5] the Aegean block, the clustering border,  
Figure 8: Comparison of clustering results with ensemble clustering for eastern Turkey with: (**a**) BIRCH; (**b**) HAC; (**c**) \(k\)-means; (**d**) mini batch \(k\)-means; (**e**) spectral clustering; (**f**) MCLA results. Red circles show the differences between algorithms. Black solid lines are the block model at [5]. The green dashed line is our block border according to the ensemble clustering result. Gray thin lines show active faults [23]. as shown in the green dashed line in Figure 9, is a bit larger than their block border, but generally is compatible. Figure 10 shows the southern part of Turkey where the African oceanic lithosphere subducts along the Cyprus trench [5].