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Long-Term Seismicity of the East Anatolian Fault System and Its Relationship With the 2023 Mw 7.8 & 7.6 Kahramanmaraş (Se Türkiye) Earthquake Doublet

Description: 

The destructive 2023 M_w 7.8 & 7.6 Türkiye doublet (abbreviated as M1 & M2) breaks multiple fault segments along the East Anatolia Fault (EAF) system, forming one of the largest continental doublets ever recorded. To understand why the 2023 event developed to such a scale, we reconstructed a high-resolution long-term earthquake catalog ranging from 2020-2023 to better characterize the EAF fault behavior before and after the mainshocks. We adopt a deep learning-driven cataloging workflow called TED (Zhou et al. 2019, 2024), i.e. Training-based Earthquake Detection that applies Self-Attention RNN (SAR) for phase picking. We downloaded continuous broad-band data from AFAD and FDSN, forming a network of 64 stations that covers the whole EAF region. Our final catalog contains 38,424 events before the 2023 doublet and 85,520 aftershocks, which is a ~3 times increase of the AFAD catalog.

We find that seismicity before the 2023 doublet are low along the ruptured segment of EAF, except for the branch fault that nucleate M1 (abbreviated as nucleation branch thereafter). Similar quiescent feature was found along the Çardak-Sürgü Fault (CSF) that is responsible for M2. This pattern agrees with the fact that the ruptured segments are strongly locked during preseismic period. We specifically analyze the seismically active nucleation branch, and found that (1) microseismicity were dynamically triggered by the 2020 M_w 6.8 event, and (2) 3 seismic swarms were developed in 6 months before the mainshock. Both observations suggest that the nucleation branch was critically stressed before the earthquake. On the eastern end of EAF rupture, i.e. the western end of 2020 rupture, seismicity revealed a sharp change in fault dip. Moreover, preliminary results show that 4 repeater sequences of M_L 2.0-2.6 exist in the gap between the 2020 & 2023 rupture, which occur both before and after the 2023 doublet, indicating fault creep. Thus, long-term seismicity helps constrain the fault coupling condition of EAF, and provides insights on the nucleation and termination of the 2023 Türkiye doublet.

Session: Illuminating Complex, Multiplet Earthquake Sequences at Kahramanmaras (Turkiye), Herat (Afghanistan), and Beyond - I

Type: Oral

Date: 5/2/2024

Presentation Time: 08:15 AM (local time)

Presenting Author: Yijian

Student Presenter: Yes

Invited Presentation: 

Authors