2024 年 10 巻 11 号 p. 276-281
Türkiye lies at the junction of three tectonic plates which drives the significant seismicity of the region. The mainshock event of M7.8 occurred on a portion of the plate boundary East Anatolian Fault and was followed approximately 9 hours later by a M7.7 aftershock on the Sürgü - Çardak Fault. Surface fault rupture of these two events extends over a distance of roughly 460 km, with both ruptures presenting typical left-lateral strike-slip geomorphology and surface rupture patterns. The investigation as part of the Geotechnical Extreme Events Reconnaissance teams included a regional assessment of the impacts to infrastructure (i.e., bridges, pipelines) as well as documentation of the geological effects (surface fault rupture, liquefaction, lateral spread, landslides). Here we present observations on rupture terminations and surface slip measurements along the M7.8 and M7.7 ruptures. Left-lateral surface displacements along the M7.8 EAF rupture were remarkably consistent, 3 to 4 m, but diminished to the south near Antakya to around 0.5 m. The M7.7 event produced the largest recorded surface displacements of consistent 7 to 8 m left-lateral offsets. Along both ruptures, the surface trace followed tectonic geomorphic features that would have been recognized in pre-rupture mapping such as linear swales, saddles, and side-hill benches. However, in other areas the ruptures are expressed by breaks across the tops of shutter ridges, through bedrock knobs, and complex arrays of en echelon pressure ridges.
