image: 1:250,000 active faults were obtained from Emre et al. (2012). The seismogenic faults of historical earthquakes were sourced from Duman and Emre (2013). Earthquake catalog was obtained from USGS (2023).
Credit: ©Science China Press
This study is led by Prof. Yue-Ren Xu at the Institute of Earthquake Forecasting, China Earthquake Administration (IEF, CEA). This article focuses on using high-resolution satellite data to rapidly assess surface ruptures caused by strong international earthquakes. Post-earthquake high-resolution satellite images have become invaluable in mapping coseismic surface ruptures induced by strong earthquakes. This study took the 2023 Türkiye earthquake doublet as an example. On February 6, 2023, twin earthquakes shook southeastern Türkiye and northwestern Syria. The first earthquake, known as the Pazarcık earthquake, occurred at 1:17 A.M. GMT (4:17 AM local time) with a moment magnitude of MW7.8 and a focal depth of 10 km. The second strong earthquake, the Elbistan earthquake, occurred 9 hours later, with MW7.5 (37.196°E, 38.011°N) and a focal depth of 7.4 km.
After the mainshocks, various post-earthquake high-resolution satellite data covered the epicenter area, providing valuable information for rapidly assessing surface ruptures. Xu’s group utilized multiple images, including the Chinese GF-series satellites (GF-2/7), the Beijing satellites (BJ-2/3), and the Maxar satellites. The spatial resolution of those images ranges from 0.3 to 0.8 m. The interpretations based on those data yielded the results: the two strong earthquakes had separate rupture zones. The first earthquake generated an approximately 280 km coseismic surface rupture along the southwestern segment of the main East Anatolian Fault (EAF), with 241 left-lateral displacements reaching up to 6.8 ± 0.68 m, particularly 40 km northeast of the epicenter. The second earthquake produced a roughly 110 km surface rupture on an east-west branch of the EAF, with maximum displacements of 7.2 ± 0.72 m. The group also compared the distribution of the surface ruptures and offsets derived from these high-resolution satellite images with the results obtained from InSAR and field measurements. They think that rapid assessment based on high-resolution remote sensing data can help scholars quickly understand the characteristics of surface ruptures caused by strong earthquakes abroad.
Based on the MW7.8 earthquake’s cascading rupture pattern, the group found that surface rupture might not always follow established recurrence intervals. During cascading ruptures, the maximum surface slip was constrained by the accumulated stress energy of individual fault segments. Despite the magnitude of the MW7.8 earthquake, its maximum surface offset was smaller than that of the MW7.5 earthquake. Xu also pointed out in this article that “the 1822 MS7.5 earthquake likely occurred on the Yesemek segment rather than the Amanos segment, preventing rupture and aftershocks from extending southward along the Narlı segment during the MW7.8 earthquake”.
Finally, the group argued that the Malatya Fault and specific EAF segments, such as the Palu, Karlıova, and Amanos segments, may pose seismic risks in the future. Hence, focusing on enhanced seismic fortification efforts in the valley regions near these fault segments is crucial.