## 3 Results
### Effect of the Barrier Strength on the Fault Rupture Process  
In order to further point out the effect of the barrier strength on the fault rupture process, we changed the magnitude of initial normal stress \(\Delta\sigma_{\mathrm{n}}\) (\(\Delta\sigma_{\mathrm{n}}/\sigma_{\mathrm{n}}=1\%\)-\(15\%\)) in the barrier and simulated more than ten different models with the classical slip-weakening friction law for a comparative analysis. Figure 7 shows the simulated velocity curves of a rupture front on a fault under different strengths of a barrier. We can see from the figure that when there was a barrier on the fault surface, the rupture process of the fault changed; when the rupture propagated to the barrier, the rupture speed of the fault obviously reduced; and when the rupture front of the fault left the barrier zone for a certain distance, the rupture speed obviously accelerated. As the barrier strength increased, the curve of rupture speed on the fault fluctuated more and more; when \(\Delta\sigma_{\mathrm{n}}/\sigma_{\mathrm{n}}\) exceeded \(3\%\), a supershear rupture zone appeared on the fault; and with the increase of \(\Delta\sigma_{\mathrm{n}}/\sigma_{\mathrm{n}}\), the propagation distance of the rupture with supershear wave velocity correspondingly increased. However, after analyzing the simulation results, it was found that the overall rupture duration of the fault was basically unchanged and slightly increased with the increase of the barrier strength. It was concluded that the barrier could not shorten the overall rupture duration of the fault, but it could regulate the distribution of the rupture speed on the fault surface and promote the fault to produce supershear rupture.  
Figure 6: (a) Distribution diagram of the rupture speed of the fault surface. (b) Distribution diagram of the slip along the interface over time.  
Figure 7: The distribution of rupture speed on the fault varies with barrier strength. The figure shows that near the barrier, the rupture speed of the fault first decreased and then rose. As the barrier strength increased, the curve of rupture speed on the fault fluctuated more and more.  
Previous studies [50] have shown that when a fault ruptures at the supershear wave velocity, the wavefronts that are formed by the new and old ruptures interfere with each other, and the superposition effect greatly increases the amplitude of the ground motion and forms Mach waves, which greatly intensify the seismic hazards. Does the supershear rupture that is induced by the barrier increase the peak ground acceleration and correspondingly lead to the enhancement of the seismic hazards? Figure 8 shows the simulated distribution of peak acceleration of the earth's surface near faults with the barrier of different strengths. It can be seen from the figure that when the barrier strength was weak (\(\Delta\sigma_{\text{n}}/\sigma_{\text{n}}\) is small), the peak ground acceleration near the fault did not obviously change. With the increase of \(\Delta\sigma_{\text{n}}/\sigma_{\text{n}}\), the barrier started to cause the fault to produce a supershear rupture, the propagation distance of supershear wave velocity was longer and longer, and the peak ground acceleration near the fault was also increasingly larger. This shows that the existence of a barrier may lead to the enhancement of seismic hazards.