Source Model of the 2023 Turkey Earthquake Sequence Imaged by Sentinel-1 and GPS Measurements: Implications for Heterogeneous Fault Behavior along the East Anatolian Fault Zone

Abstract

On 6 February 2023, a devastating doublet of earthquakes with magnitudes of Mw 7.8 and Mw 7.6 successively struck southeastern Turkey near the border of Syria. The earthquake sequence represents the strongest earthquakes in Turkey during the past 80 years and caused an extensive loss of life and property. In this study, we processed Sentinel-1 and GPS data to derive the complete surface displacement caused by the earthquake sequence. The surface displacements were adopted to invert for the fault geometry and coseismic slip distribution on the seismogenic faults of the earthquake sequence. The results indicate that the coseismic rupture of the Turkey earthquake sequence was dominated by left-lateral strike slips with a maximum slip of ~10 m on the East Anatolian Fault Zone (EAFZ) and the Sürgü fault (SF). Significant surface ruptures are recognized based on the geodetic inversion, which is consistent with the analysis of post-earthquake satellite images. The cumulative released moment of the two earthquakes reached 9.62 × 1020 Nm, which corresponds to an event of Mw 7.95. Additionally, the interseismic fault slip rates and locking depths along the central and western segments of the EAFZ were estimated using the high-resolution long-term velocity field. The results reveal significant lateral variations of fault slip rates and locking depths along the central and western segments of the EAFZ. Generally, the estimated fault locking zone showed good spatial consistency with the coseismic fault rupture of the Mw 7.8 shock on the EAFZ. The static coulomb failure stress (CFS) change due to the Mw 7.8 earthquakes suggests that the subsequent Mw 7.6 event was certainly promoted by the Mw 7.8 shock. The stress transfers from the fault EAFZ to the fault SF were realized by unclamping the interface of the fault SF, which significantly reduces the effective normal stress on the fault plane. Large CFS increases in the western Puturge segment of the EAFZ, which was not ruptured in the 2020 Mw 6.8 and the 2023 Mw 7.8 earthquakes, highlight the future earthquake risk in this fault segment.

Complex multi-fault rupture and triggering during the 2023 earthquake doublet in southeastern Türkiye

“…3a ). This pattern aligns closely with published models 36 – 38 , highlighting the presence of lateral variations in tectonic stress, frictional properties within the crust, and intricate fault zone structures along the rupture. The estimated seismic moment M 0 = 7.1 × 10 20 N·m ( M W = 7.82) during 90 s of coseismic rupture is slightly larger than the GCMT point-source solution (M 0 = 6.1 × 10 20 N·m).…”

Multi‐Instrument Observations of Various Ionospheric Disturbances Caused by the 6 February 2023 Turkey Earthquake

“…The focal mechanism of the earthquake of interest was strike‐slip (M. Li et al., 2023; S. Li et al., 2023), and from the literature (Astafyeva, 2019; Astafyeva et al., 2014), we know that despite the coseismic displacement being mainly horizontal, such earthquakes are expected to generate ionospheric disturbances as well. As stated in Astafyeva (2019), it is still under debate if the amplitude of disturbances caused by strike‐slip is comparable with the ones caused by dip‐slip earthquakes of the same magnitude.…”

“…The focal mechanism of the earthquake of interest was strike-slip (M. S. Li et al, 2023), and from the literature (Astafyeva, 2019;Astafyeva et al, 2014), we know that despite the coseismic displacement being mainly horizontal, such earthquakes are expected to generate ionospheric disturbances as well.…”

“…The work of Leonard and Barnes (1965) and Davies and Baker (1965) concerning the great Alaskan earthquake of 1964, has already demonstrated that major earthquakes can cause disturbances in the ionosphere. Since then, it has been established that these ionospheric disturbances are manifested as different types of earthquake induced traveling ionospheric disturbances (TIDs), propagating through different mechanisms (Astafyeva, 2019; Brissaud & Astafyeva, 2022; M. Li et al., 2023; S. Li et al., 2023; Meng et al., 2019).…”

“…This complementary view from observations from different instruments, is ideal for detecting different disturbance types (Astafyeva, 2019; Meng et al., 2019). A lot of recent research has focused on the detection of ionospheric signatures of earthquakes in GNSS data or in satellite data (M. Li et al., 2023; S. Li et al., 2023; Maletckii & Astafyeva, 2021; Ruan et al., 2023; Yang et al., 2022), because for much of the globe these are the only available observations. However, in the European region, more types of instruments are available in relatively dense observational networks (see Figure 1).…”