Some of the earliest adoption of digital technologies began in the late 1990’s and in particular were introduced during field reconnaissance work after the 1999 Turkey Kocaeli and Düzce earthquakes (Ansal et al., 1999). It is thus of significance that following the February 6, 2023 Kahramanmaraş-Türkiye Earthquake Sequence, the next step in advancing the role of digital technologies in post disaster reconnaissance was introduced through the extensive utilization of real-time integrated digital database systems including SiteEye and Filio. The use of these technologies resulted in immediate access to data being acquired by field team members and facilitated the day to day planning of reconnaissance activities for a large coordinated effort involving more than 100 individuals (Cetin et al., 2023). This paper discusses how this rich integration was achieved as well as demonstrates how the immediate access to data facilitated an efficient phased approach to reconnaissance activities.

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.

The 2023 Türkiye/Syria earthquake sequence includes the February 6 M7.8 mainshock followed approximately nine hours later by a M7.7 aftershock, and many smaller aftershocks including a M6.8 and M6.3 on February 6 and 20, respectively. These events occurred in a region near the plate boundary of the East Anatolian Fault, in the proximity of which numerous ground motion recordings sites had been installed north of the Türkiye/Syria border. As a result, the events were well recorded both near the fault and at rupture distances up to 570 km. We describe the available recordings and component-specific data processing performed with the aim of optimizing usable bandwidth. The resulting database includes 310, 351, 291, and 229 usable three-component recordings from the M7.8, M7.7, M6.8, and M6.3 events, respectively. We also present source, path, and site metadata that was compiled according to uniform protocols. Comparisons to a global ground motion model (GMM) for active tectonic regions and a local, Türkiye-specific model demonstrate the existence of complex path effects that result in relatively poor fits between the GMMs and observed data at large distances (generally R_JB > 200 km). Under-predictions at some stations may be influenced by directivity and/or basin effects that affect the ground motions but that are not accounted for directly in the GMMs. We also present analysis of spatial variability of peak ground acceleration for the M7.8 mainshock. A residual map produced from this analysis demonstrates that the global GMM over-predicts on the Anatolian block and under-predicts on the Arabian block, further supporting the existence of complex attenuation features in the region.

Following the M7.8 and M7.6 Pazarcik and Elbistan-Kahramanmaras-Turkiye earthquake sequence, 81 soil liquefaction sites with surface manifestations in the form of soil ejecta, lateral spreading, and/or excessive settlement were studied. This paper presents the results of preliminary liquefaction susceptibility assessments performed at a suite of these soil sites. Soil classification tests were performed on potentially liquefiable soil layers and the retrieved ejecta. The classification test results revealed that clean sands and non-plastic silts are vulnerable to seismic soil liquefaction. Moreover, low to high plasticity clayey ejecta collected at Adiyaman-Golbasi and Hatay Airport sites confirmed that clayey soils with plasticity index values as high as 37%, liquefied during the events.

The 2003 M_w 7.8 Kahramanmaras earthquake produced strong shaking that triggered widespread liquefaction in parts of the port city of Iskenderun, Turkiye. Liquefaction was largely observed near the city’s shoreline, with severe liquefaction and liquefaction-induced building settlement concentrated in the reclaimed land of the Cay District of Iskenderun. This paper presents some of the key observations of liquefaction-induced building and ground settlement documented in the Cay District. Lidar scans and laser-level hand measurements were used to capture building settlements ranging from 0 to 740 mm. The patterns of building and ground settlement indicated they were related. The ground surrounding buildings that settled significantly was deformed downward up to 6 m from the building. The simultaneous warping of the ground from two nearby buildings resulted in a “hogging” or convex ground deformation pattern between the two buildings. In one case, the lidar scans captured hogging ground deformation between a group of four buildings with similar age and construction, and in another case, a lightly-loaded building was damaged by the hogging ground deformation induced by settlement of two adjacent buildings.

Presented here is select observations of the seismic performance of earth dams and port facilities from the 2023 Turkiye Earthquakes. The 2023 Februrary 6^th events included a M7.8 and M7.7 within 9 hours of each other on separate but adjacent faults. Ground shaking was recorded throughout the region with median values at roughly one half gravity. Seventeen earth dams experienced some type of geotechnical damage due to liquefaction, fault rupture, or seismic compression. Several ports facilities were also impacted by liquefaction and/or lateral spreading. A synopsis of key geotechnical earthquake damage patterns is presented.