## 3 Results  
Based on the re-picking phase and distribution of available BMKG stations, we determined the location of the hypocenter using the NonLinLoc Global mode. The estimated mean error in x, y, and z directions using the covariances values are 10,198 km, 14,081 km, and 19,035 km, respectively. The distribution frequency estimated error location in the x, y, and z directions is shown in Figure S9. The distribution between the number of events and the azimuthal gap is shown in Figure S10, and the epicentral distance distribution is shown in Figure S11. We limit the value of travel time residuals in the range of \(-10\leq\) initial travel time residuals (itr) \(\leq\) 10 to control the quality of the input data for the tomographic inversion process. The bad picks can be traced in unit 20 of simulps output file, as shown in Figure S12. Before the inversion, the initial travel time residual values varied in the range of \(-9.993\) s to 9.858 s, with a mean value of \(-1.111\) s. After inversion, the final travel time residuals varied in the range of \(-7.148\) to 6.197 s, with a mean value of 0.156 s, forming a Gaussian distribution centered around 0 s. Tomographic inversion achieved the conver  
Figure 4: The horizontal and vertical seismic map of the research location in the Molucca Collision Zone. The bold black lines A-A\({}^{\prime}\) (south–north), B-B\({}^{\prime}\) (south–north), C-C\({}^{\prime}\) (west–east), D-D\({}^{\prime}\) (west–east) denote the areas of the vertical cross-section tomography. The black plus sign represents the distribution of the grid nodes for tomographic inversion; the colored dots indicate the distribution of earthquakes; the blue triangles are BMKG stations, and the black triangles signify volcanoes. gence after the 15 th iteration with the weighted Root Mean Square (RMS) residual reduced by 47%, initially from 0.82312 s down to 0.43871 s (Figure S13). The RMS residual before the inversion ranged from 0.06 to 1.26 s with an average value of 0.54 s. After inversion, the range of values was down to 0.04 to 0.83 s with a mean value of 0.36 s (Figure S14) or reduced by about 33%. The Interpretation of the tomogram becomes valid and has a high confidence level by performing a resolution test of the seismic tomography model. Therefore, we present the CRT results shown in Figure 5 for Vp and Vp/Vs of profiles A-A\({}^{\prime}\), B-B\({}^{\prime}\), C-C\({}^{\prime}\), and D-D\({}^{\prime}\) and Figure S15 horizontal section for Vp and Vp/Vs with the recovered area is delineated by dashed purple lines. The CRT positive recovery for A-A\({}^{\prime}\) is beneath the Gorontalo Basin, Sulawesi's north arm, and the Celebes Sea up to a depth of 210 km. The CRT positive recovery for the B-B\({}^{\prime}\) profile is beneath the Halmahera Volcanic Arc up to a depth of 240 km; for profile C-C\({}^{\prime}\) the CRT positive recovery is shown beneath the Celebes and Molucca Seas, and the Morotai Basin up to a depth of 210 km. For profile D-D\({}^{\prime}\), the CRT positive recovery is beneath Sulawesi's north arm, the Molucca Sea, and Halmahera Island up to a depth of 300 km. These results are consistent with the density distribution of P- and S-rays as revealed by the DWS, RHC, and DRE results (Shown in Figures S6-S8); the highest Vp and Vp/Vs values are listed in Table S1. The primary resolution test we used to interpret the tomographic results was the CRT, supported by the DWS, RHC, and DRE results. Hence, this research focused on the travel time tomography results in four areas in the subduction zone beneath Sulawesi's north arm, the subduction zone beneath the Halmahera Volcano Arc, and the double subduction zone of the Molucca Sea. Tomographic inversion results of cross-section A-A\({}^{\prime}\), as shown in Figure 6 as follows:  
Figure 5: The vertical cross-section of CRT profiles.