## 4 Results and Discussion
### Crustal Architecture of the High-Magnetism Bodies  
To verify the reliability of our model, a multiple deep seismic reflection profile from [PERSON] et al. (2018) [10] (Figure 9 and profile line (SS) in Figure 1) and an OBS profile from [PERSON] et al. (2011) [7] were compared with the model (Figures 9 and 10). The results show that our model aligns well with the multiple deep seismic reflection data, confirming the credibility of the model. As previously mentioned, the Dongsha Rise exhibits significant high-magnetic anomalies, which correspond to high-magnetism bodies revealed at depths of 20-30 km in the model. In addition, the multiple deep seismic reflection profile reveals a Moho discontinuity beneath the Dongsha Rise (at 125 km along the profile), with a high-velocity body in the lower crust at this location. Our model further indicates that the high-magnetism body beneath the Dongsha Rise is situated at the bottom of the lower crust, with its planar position and depth in good agreement with the distribution of the high-velocity body in the lower crust.  
Figure 8: (**a**) Calculated magnetic anomalies of the inversion model and (**b**) residuals between calculated and real magnetic anomalies. Black lines represent the 0 m isobath. White lines represent the depressions.  
Figure 7: Three-dimensional prospective map of our crustal susceptibility model in the northern SCS. Only susceptibility greater than 0.02 (SI) is displayed in green, with red representing 0.03 (SI). Black lines represent 0 m isobath.  
The crustal velocity model of the OBS2006-3 profile across the Dongsha Rise (profile line @ in Figure 1, [7]) shows that the upper crust is relatively thick, exceeding 10 km, and has an anomalous uplift at the base of the upper crust, with a P-wave velocity (Vp) of up to 6.9 km/s. The lower crust is approximately 12 km thick, with a Vp of 7.4 km/s, and exhibits a pronounced uplift. This uplift corresponds well with the horizontal position and depth of the high-magnetism bodies revealed by our susceptibility model, suggesting that crustal thickening and velocity anomalies may be due to mantle-derived, mafic, high-magnetism, and high-density material migrating upward. The intense magmatic activity led to the formation of a high-velocity layer in the lower crust that extends laterally on both sides.  
To more clearly illustrate the spatial distribution of high-magnetism bodies, four different profiles were selected for visualization, with the susceptibility distribution and positions shown in Figure 11. The base map represents a horizontal slice of the model at a depth of 25 km, displaying the distribution characteristics of high-susceptibility bodies, primarily composed of intermediate to mafic rocks. The horizontal slice reveals that the peak susceptibility of anomalous bodies (approximately 0.04 SI) forms an NE-trending belt along the Dongsha Rise, with large areas of relatively high-magnetism material (approximately 0.02 SI) and scattered high-magnetism material (approximately 0.03 SI) distributed to the north of the belt. The vertical profiles indicate that the high-magnetism bodies are primarily located in the lower crust (at depths of 20-30 km), suggesting that the high-magnetic anomaly zone in this area is caused by deep, large-scale igneous bodies, which is consistent with the findings of [24]. The magnetization characteristics of the high-magnetic anomaly belt may reflect stronger magmatic activity during the expansion process, similar to the  
Figure 10: Comparison of the susceptibility model (**below**) with the OBS2006-3 P-wave velocity model (**above**) [7]. The red circle in the above map highlights the high-velocity uplift.  
Figure 9: The susceptibility model superimposed the multiple deep seismic reflection profile [10].  
residual magma chambers of fast-spreading mid-ocean ridges. This may challenge the traditional \"low-magma\" expansion model of the SCS, requiring a reassessment of the expansion rate and magma supply mechanisms.