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Abstract:
On February 6, 2023, two large earthquakes with moment magnitudes of 7.8 and 7.5 occurred in Southeastern Turkey. These two earthquakes caused significant damage and a high number of fatalities in the provinces of Kahramanmaras, Hatay, Adiyaman, Osmaniye, Gaziantep, Kilis, Sanliurfa, Diyarbakir, Malatya, Adana, and Elazig. A dense array of seismograms close to the fault ruptures recorded both earthquakes. Some of these records are observed to have very large amplitudes with peak ground acceleration values over 1 g and peak ground velocity values over 150 cm/s. This study provides a detailed analysis of the recorded ground motions and investigates potential reasons behind the significant structural damage and observed extreme motions with very high amplitudes. These reasons include multi-segment fault ruptures, multiple high-amplitude wave packets observed in the records, rupture directivity effects, and the occurrence of strong velocity pulses. The recorded ground motions are also compared to the current and previous seismic codes of Turkey for various return periods. Next, shaking intensities in terms of the Modified Mercalli Intensity (MMI) scale are estimated using empirical models which relate peak ground motion parameters to the felt intensity. These estimates are then compared to the reported intensity values from field observations. Discrepancies between the estimated and reported intensity values are investigated.
