5:15 PM - 6:45 PM
[SSS10-P03] Strong Ground Motion Simulations and Effect of Rupture Velocity in the Near-Fault Region during the 6 February 2023 Türkiye Earthquake
Keywords:Near-fault region, Permanent Displacement, Rupture Velocity
1. Introduction
During the 2023 Türkiye Earthquake that occurred on February 6, 2023, many strong-motion records were obtained in the Near-Fault Region. First, we construct a characterized source model and reproduce the long-period component including permanent displacement in the Near-Fault Region using the wavenumber integration method. Next, we reproduce strong-motion records with EGF. Finally, we discuss the effect of rupture velocity on the strong-motion prediction results.
2. Characterized Source Model
We construct a characterized source model for the Amanos segment of the 2023 Türkiye Earthquake based on strong ground motion prediction method by the Headquarters for Earthquake Research Promotion (hereinafter called "Recipe"). Besides, we expand the Recipe based on the above mentioned results for shallower region than the seismogenic layer by tanaka et al.(2018). We recommend the regularized Yoffe-type slip velocity functions for shallower region than the seismogenic layer. We use a subsurface structural model based on Güvercin et al. (2022). Based on a subsurface structural model, the upper depth of the seismogenic layer is assumed to be 2 km. The fault length is 148 km and is modeled in 13 segments. The asperity location and rupture starting points and rupture velocity of individual segments were established by trial and error. Super Shear Rupture is assumed for a portion of stations 2718 to 3145. The source fault model is shown in Figure 1.
3. The Seismic Wave Simulation
The calculation results by the wavenumber integration method are shown in Fig. 2 in comparison with the observation record. The period covered by the calculation was set to 2 seconds or longer. At the northern stations, especially at stations 2718 and 3143, the results of the wavenumber integration method reproduce well the characteristics of the strong-motion records including permanent displacements. Next, we simulate the observed records by EGF for 2718 and 3143 stations, where EGF only considers within the seismogenic layer of seg3-4 to seg3-8. A comparison between the EGF-based waveform synthesis results and the observation record is shown in Fig. 3. The period covered by the calculations ranged from 0.1 to 4 seconds. At 2718 stations, the EGF calculation results reproduce the characteristics of the strong-motion records well.
4. Influence of Rupture Velocity on Strong Ground Motion Prediction Results
A comparison of the calculated results by EGF for the rupture velocity of Vr=2.45 km/s (Vr=0.72Vs) and Vr=3.06 km/s (Vr=0.9Vs) is shown in Fig. 3. When the Super Shear Rupture occurs on the forward side (north in this case), as at station 3143, a slightly faster rupture propagation velocity (Vr=0.9Vs) than the Recipe can be considered to obtain an amplitude close to the observed record. On the other hand, if the Super Shear Rupture does not occur on the forward side, as at station 2718, it is overestimated. Uncertainty of rupture velocity that should be considered in seismic ground motion prediction needs to be continued to be studied.
Acknowledgments
We have used seismic records published by AFAD and ESM. GMT was used to create some of the figures. We would like to thank the following for their cooperation.
During the 2023 Türkiye Earthquake that occurred on February 6, 2023, many strong-motion records were obtained in the Near-Fault Region. First, we construct a characterized source model and reproduce the long-period component including permanent displacement in the Near-Fault Region using the wavenumber integration method. Next, we reproduce strong-motion records with EGF. Finally, we discuss the effect of rupture velocity on the strong-motion prediction results.
2. Characterized Source Model
We construct a characterized source model for the Amanos segment of the 2023 Türkiye Earthquake based on strong ground motion prediction method by the Headquarters for Earthquake Research Promotion (hereinafter called "Recipe"). Besides, we expand the Recipe based on the above mentioned results for shallower region than the seismogenic layer by tanaka et al.(2018). We recommend the regularized Yoffe-type slip velocity functions for shallower region than the seismogenic layer. We use a subsurface structural model based on Güvercin et al. (2022). Based on a subsurface structural model, the upper depth of the seismogenic layer is assumed to be 2 km. The fault length is 148 km and is modeled in 13 segments. The asperity location and rupture starting points and rupture velocity of individual segments were established by trial and error. Super Shear Rupture is assumed for a portion of stations 2718 to 3145. The source fault model is shown in Figure 1.
3. The Seismic Wave Simulation
The calculation results by the wavenumber integration method are shown in Fig. 2 in comparison with the observation record. The period covered by the calculation was set to 2 seconds or longer. At the northern stations, especially at stations 2718 and 3143, the results of the wavenumber integration method reproduce well the characteristics of the strong-motion records including permanent displacements. Next, we simulate the observed records by EGF for 2718 and 3143 stations, where EGF only considers within the seismogenic layer of seg3-4 to seg3-8. A comparison between the EGF-based waveform synthesis results and the observation record is shown in Fig. 3. The period covered by the calculations ranged from 0.1 to 4 seconds. At 2718 stations, the EGF calculation results reproduce the characteristics of the strong-motion records well.
4. Influence of Rupture Velocity on Strong Ground Motion Prediction Results
A comparison of the calculated results by EGF for the rupture velocity of Vr=2.45 km/s (Vr=0.72Vs) and Vr=3.06 km/s (Vr=0.9Vs) is shown in Fig. 3. When the Super Shear Rupture occurs on the forward side (north in this case), as at station 3143, a slightly faster rupture propagation velocity (Vr=0.9Vs) than the Recipe can be considered to obtain an amplitude close to the observed record. On the other hand, if the Super Shear Rupture does not occur on the forward side, as at station 2718, it is overestimated. Uncertainty of rupture velocity that should be considered in seismic ground motion prediction needs to be continued to be studied.
Acknowledgments
We have used seismic records published by AFAD and ESM. GMT was used to create some of the figures. We would like to thank the following for their cooperation.