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Why Did the Pulse-Like Ground-Motion Differ Three Times in Pgv and Tp Within a 3 Km Wide Near-Fault Region of the 2023 Mw 7.8 Turkiye Earthquake?

Description: 

Over 25 pulse-like velocity (VP) waveforms were observed in the near-fault region of the 2023 Turkiye Mw 7.8 earthquake, which were extracted by Shahi and Baker’s (2014) method. The extracted pulse-like ground motions have a peak ground velocity (PGV) and pulse period (Tp) range of 25 to 184.2 cm/s and 1.8 to 15.6 s, respectively, which were in a distance range of rupture distance (R_rup) within 0.33 to 54 km. Significant intensity differences in the VP were observed at three stations within a 3 km wide near-fault region, Antakya, one of the major disaster regions, and observed as the second-largest PGV of the extracted VPs. The R_rup of the three stations is 0.33, 2.1, and 3.5 km for station codes 3126, 3123, and 3131, respectively. However, the corresponding extracted PGV and Tp showed a two- to three-times difference within the three stations from PGV of 119.9, 175.4, and 60.3 cm/s and Tp of 3.4, 2.6, and 13.2 s. This is difficult to explain by the median prediction of the modern nonergodic ground motion models. In this study, by removing a possible cause from the coseismic static offset (fling step), the directivity pulse is evaluated by the velocity-pulse simulation procedure (Huang et al., 2024), which is derived from the stochastic finite-fault ground-motion simulation method, a baseline correction method, and a fling-step removal model. The result indicated that the directivity pulse provides a 50 to 60 cm/s PGV, which was recorded by the rock site 3131 and enlarged two times from linear site response and recorded by the softest soil site 3126. The three times PGV observed at 3123 was generated by simultaneously linear site response and a super shear behavior at the near-source portion. The closest station, 3126, did not suffer the highest PGV in this region because of the soil nonlinearity in the latter portion of the S arrival. Finally, the longest 13.2 s Tp is caused by a 130 cm coseismic deformation from the fling-step, which occurred after the VP arrival and did not show an apparent longer period in the other two stations.

Session: From Earthquake Recordings to Empirical Ground-Motion Modelling - III

Type: Oral

Date: 5/2/2024

Presentation Time: 03:00 PM (local time)

Presenting Author: JyunYan

Student Presenter: No

Invited Presentation: 

Authors