The Destructive Earthquake Doublet of 6 February 2023 in South-Central Türkiye and Northwestern Syria: Initial Observations and Analyses

Abstract

On 6 February 2023, two large earthquakes with magnitude 7.8 and 7.6 rocked south-central Türkiye and northwestern Syria. At the time of writing, the death toll exceeded 50,000 in Türkiye and 7200 in Syria. The epicenter of the first mainshock was located ∼15 km east of the east Anatolian fault (EAF), the second large earthquake (9 hr later) initiated ∼90 km to the north on the east–west-trending Sürgü fault. Aftershocks delineate fault lengths of ∼350 and ∼170 km, respectively. Using satellite and seismic data for first-order analyses of surface-fault offsets, space–time rupture evolution, and recorded ground motions, our study sheds light on the reasons for the extensive destruction. The first event ruptured the EAF bilaterally, lasted for ∼80 s, and created surface fault offsets of over 6 m. The second event also ruptured bilaterally with a duration of ∼35 s and more than 7 m surface offsets. Horizontal ground accelerations reached locally up to 2g in the first mainshock; severe and widespread shaking occurred in the Hatay-Antakia area with values near 0.5g. Both earthquakes are characterized by directivity effects and abrupt rupture cessation generating stopping phases that contributed to strong seismic radiation. Shaking was further aggravated locally by site-amplification effects.

Laboratory Earthquake Rupture Interactions With a High Normal Stress Bump

“…At large scales, earthquake gates can cause complex long‐term event histories with the behavior determined by stress conditions and other physical conditions (e.g., Rodriguez Padilla et al., 2022). Rupture complexities are manifest as complex source time functions (e.g., Yin et al., 2021) or as speedups and slowdowns in rupture velocity, that might be detectable with back‐projection imaging (e.g., Mai et al., 2023; Meng et al., 2011). Our experiments show that this can also happen at a smaller scale: distinct rupture phases initiate and terminate as mediated by the bump.…”

Multi‐Scale Rupture Growth With Alternating Directions in a Complex Fault Network During the 2023 South‐Eastern Türkiye and Syria Earthquake Doublet

“…Although our sole use of teleseismic data may not rigorously discriminate the absolute location of the slip on the closely located parallel faults, we favor that the apparent back-propagating part of the rupture occurred on the main EAF because of the higher potency rate on the main EAF model fault rather than on the splay model fault (Figures 2c and 2d). This assumption is supported by independent modeling using geodetic datasets that finds larger slip along the main EAF than on the splay fault (Barbot et al, 2023;Mai et al, 2023;Melgar et al, 2023).…”

Dynamic Rupture Process of the 2023 Mw 7.8 Kahramanmaraş Earthquake (SE Türkiye): Variable Rupture Speed and Implications for Seismic Hazard

“…The red line is the simulation result, and the black line is the data provided by Mai et al. (2023). The two blue dashed lines represent the intersections of Nurdağı‐Pazarcık Fault (left) and F3 (right) with East Anatolian Fault, respectively.…”

“…The detailed investigation results of surface rupture have not been seen yet, hence the surface strike‐slip is compared with the on‐fault displacement measured by Mai et al. (2023) based on the satellite data (Liu, Hu, Li, Ma, Shi, et al., 2022; Liu, Hu, Li, Ma, Wu, et al., 2022; Figure 3e). We have captured the first‐order characteristics of surface displacement.…”

“…After the 2023 doublet sequence, many preliminary results of finite-fault source inversion based on strong ground motion, near-field geodetic data and/or teleseismic data have been published (Delouis et al, 2023;Mai et al, 2023;Melgar et al, 2023;Goldberg, Taymaz, Reitman, et al, 2023, Goldberg, Taymaz, Yeck, et al, 2023Okuwaki et al, 2023;Xu et al, 2023). However, a highly debated controversy exists regarding the presence of a supershear rupture during the Mw 7.8 event.…”