Browsing by Author "Tobita, Tetsuo"

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Influence of Local Soil Conditions on Damages in Kahramanmaras during the 2023 Turkey Earthquake
(Springer Science and Business Media Deutschland GmbH, 2025) Milev, Nikolay; Kiyota, Takashi; Tobita, Tetsuo; Briones, Juan; Briones, Othon; Cinicioglu, Ozer; Torisu, Seda
The 2023 Turkey-Syria earthquake affected an area of 99000 km2 on Turkish side where two million people were left without home. The PGA values which have been recorded by various stations show values as high as 1.2g as well as relatively spectacular maximum vertical component (PGV). The focus of the paper is to focus on a noticeable phenomenon in the city of Kahramanmaras where, on one hand, almost all buildings in the historical centre have either collapsed or been severely damaged by the two earthquakes (Pazarcik at 4:17 AM and Elbistan at 1:24 PM, respectively) of February 6th 2023, whereas, on the other hand, structures in the surrounding areas have significantly less damage. Moreover, it is evident from seismic stations’ recordings that impact (in terms of PGA, acceleration and velocity time histories) of first major shock (M7.7 Pazarcik) is higher than the one of the second major shock (M7.6 Elbistan) at similar magnitude and comparable distance to the epicenter. For the sake of investigating further the influence of local soil conditions as possible reason for the observed events shear wave velocity and soil deposit fundamental frequency have been measured in two spots – first, where multiple collapsed structures were detected and second, a neighbouring area with mostly standing buildings. Results indicate that the on-site measurement of only S-waves might lead to wrong assumptions in terms of microseismical zonation and further considerations shall be accounted. Furthermore, some comments and preliminary assumptions regarding seismic motion amplification effects have been presented in the study. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.
Citation - WoS: 21
Citation - Scopus: 25
Geotechnical Damage Survey Report on February 6, 2023 Turkey-Syria Earthquake, Turkey
(Japanese Geotechnical Soc, 2024) Tönük, Gökçe; Shiga, Masataka; Çinicioğlu, Özer; Tobita, Tetsuo; Kiyota, Takashi; Milev, Nikolay; Torisu, Seda
In response to the significant earthquakes that struck Turkey and Syria on February 6, 2023, a collaborative reconnaissance team, consisting of researchers and engineers from Japan and Turkey, was formed by the Japan Association for Earthquake Engineering, the Architectural Institute of Japan, the Japan Society of Civil Engineers, and the Japanese Geotechnical Society. This coalition conducted an in-depth on-site investigation from March 28 to April 2, two months after the catastrophic seismic events. In Islahiye, a landslide resulted in the formation of a landslide dam. Another landslide occurred in Tepehan on a relatively gentle slope formed of limestone, with possible correlations to fault movements. Iskenderun encountered not just building collapses on soft ground, but also instances of the tilting of buildings and ground subsidence attributed to the liquefaction of reclaimed coastal soil. Golbasi witnessed significant liquefaction-induced damage to structures with shallow foundations on soft ground, involving tilting and settling. However, a more comprehensive investigation is required to accurately map the extent of the liquefied soil layers. Antakya and Kahramanmaras emerged as regions where building damage coincided with surface ground vibrations. Despite severe building collapses, Antakya's relatively stable ground showed an average S-wave velocity exceeding AVS30 400 m/s. This suggests potential wave amplification due to underlying geological structures. Kahramanmaras displayed notable building damage concentrated in alluvial fan formations. (c) 2023 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BYNC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).