Figure 8. Numerical results of Scenario 5. (a) shows the stress change distribution; (b) shows the total slip distribution. (c) shows the rupture time contour with an interval of 5 seconds; the red curves indicate that the rupture front reaches the trench at 47.5 s. (d) shows the rupture velocity distribution. (e) shows the along-dip profiles of rupture velocity along the central line (red line in (d)) and along 50 km away along-strike from the central line (black line in (d)). The crosses in (d) and indicate the locations of the two on-fault stations.
Slip rate time histories (Figure 9a) at the two stations from this scenario show that the shallow station has similar peak slip rate with more high-frequency signals compared with the deep station (Figure 9b). The amplitude spectra at the two stations from this scenario does not show clear high-frequency depletion at the shallow station compared with the deep station, also in contrast to all other scenarios. Comparing with Scenario 1 at the shallow station (Figure 9c), the upper plate low-velocity layers enhance high-frequency seismic radiation at shallow depth, in contrast to causing high-frequency depletion there in other scenarios. Comparing with Scenario 2 at the shallow station (Figure 9e), in conjunction with Figure 5e, we find that it is the high-frequency enhancement from the low-velocity layers that cause a complex feature at ~2Hz in high-frequency depletion in Scenario 2, as described in an earlier section. Scenario 2 has both depth-varying fault friction and depth-varying velocity structure. The former causes significant high-frequency depletion at the shallow station, while the latter cause high-frequency enhancement. At most frequencies above ~0.2 Hz, high-frequency depletion from depth-varying fault friction dominates over high-frequency enhancement from depth-varying velocity structure, except at ~ 2 Hz. At the deep station, Scenario 5 is also rich in high frequency content comparing to Scenario 1 (Figure 9d), while it is more depleted in high frequency content comparing to Scenario 2 at frequency > 2 Hz (Figure 9f).