## 3 Results
Profile A-A\({}^{\prime}\) (south–north), B-B\({}^{\prime}\) (south–north), C-C\({}^{\prime}\) (west–east), and D-D\({}^{\prime}\) (west–east) are vertical cross-sections of the CRT recovery model from the inversion process. The purple dashed line is the positive CRT recovery area for tomographic interpretation. The first column is Vp perturbation, the second column is Vp/Vs perturbation, and the red triangles signify volcanoes. Tomographic inversion results of cross-section B-B', as shown in Figure 7 as follows:  
Figure 6: Vertical cross-section of A-A\({}^{\prime}\) (south–north) of the Molucca Sea Plate, crossing the Minahasa Peninsula, Sulawesi’s north arm, and the Celebes Sea. The red color indicates low velocity and low Vp/Vs ratio, and the blue color indicates high velocity and high Vp/Vs ratio. The A1 and A2 are areas for the interpretation of tomographic inversion results. The black dots signify earthquakes within a radius of 30 km \(\leq\) A-A\({}^{\prime}\)\(\leq\) 30 km, and the yellow stars are significant earthquakes. The green line and the green three-dimensional surface plot are the slab2 models of the Molucca Sea Plate. The yellow line is the slab2 model of Sulawesi (2015). NST is the North Sulawesi Trench. The red triangles signify volcanoes. The blurred area is an area that is not well-resolved. Tomographic inversion results of cross-section C-C\({}^{\prime}\), as shown in Figure 8 as follows:  
Figure 7: Vertical cross-section of B-B\({}^{\prime}\) (south–north) crossing beneath the Halmahera Volcanic Arc. The red color indicates low velocity and low Vp/Vs ratio. The blue color indicates high velocity and high Vp/Vs ratio. The B1, B2, and B3 are areas for the interpretation of tomographic inversion results. The green line and the green three-dimensional surface plot are the slab2 models of the Molucca Sea Plate [45]. The black dots signify earthquakes within a radius of 30 km \(\leq\) B-B\({}^{\prime}\)\(\leq\) 30 km. SeT: Serum Trench; HT: Halmahera Trench; Bi: Bibinoi Volcano; Bs: Batusibela Volcano; Am: Amasing Volcano; Br: Buku-Rica Volcano; Rr: Rogi-Rogi Volcano; Ja: Jailolo Volcano; To: Todoko-Ranu Volcano; Ga: Gamkonora Volcano; Ib: Ibu Volcano; Tb: Tobaru Volcano. The blurred area is an area that is not well-resolved. Tomographic inversion results of cross-section D-D\({}^{\prime}\), as shown in Figure 9 as follows:  
Figure 8: Vertical cross-section of C-C\({}^{\prime}\) (west-east) crossing the Celebes Sea, Sangihe Island, Molucca Sea, and Morotai Basin. The red color indicates low velocity and low Vp/Vs ratio. The blue color indicates high velocity and high Vp/Vs ratio. The C1, C2, and C3 are areas for the interpretation of tomographic inversion results. The black dots signify earthquakes within a radius of 30 km \(\leq\) C-C\({}^{\prime}\)\(\leq\) 30 km, and the yellow star is a significant earthquake. The green line and the green three-dimensional surface plot are the slab2 models of the Molucca Sea Plate, and the brown line is the slab2 model of the Philippines [45]. ST: Sangihe Trench; HT: Halmahera Trench; the blurred area is an area that is not well-resolved. Three-dimensional tomographic inversion results combine cross-section profile A-A\({}^{\prime}\) and profile D-D\({}^{\prime}\), as shown in Figure 10 as follows:  
Figure 9: Vertical cross-section of D-D\({}^{\prime}\) (west–east) crossing Sulawesi’s north arm, the Molucca Sea, and Halmahera Island. The red color indicates low-velocity areas and low Vp/Vs ratio, and the blue color indicates high-velocity areas and high Vp/Vs ratio. The D1, D2, D3, D4, and D5 are areas for the interpretation of tomographic inversion results. The black dots signify earthquakes within a radius of 30 km \(\leq\) D-D\({}^{\prime}\)\(\leq\) 30 km, and the yellow star is the magnitude of a significant earthquake. The green line and the green three-dimensional surface plot are the slab2 models of the Molucca Sea Plate; the yellow line is the slab2 model of Sulawesi [45].