Characteristics of records obtained at the 14 November 2021 Fin doublet events, Southern of Iran

On 14 November 2021, doublet earthquakes with magnitude 6.1 and 6.3 occurred near Fin town, in the north region of the Persian Gulf, Iran. This paper analysed the ground motion characteristics of records obtained during the 2021 Fin doublet earthquakes. The different features of these events in the far and near distances have been compared with an update local ground motion prediction equation proposed for Iran. The peak ground acceleration (PGA) and spectral acceleration of records at the 2021 Fin doublet earthquakes are also compared with the 2012 Ahar–Varzaghan doublet events. Analysis of ground motions illustrated that the attenuation rate for the PGA and the spectral accelerations at a short period of 0.2 s is higher than Ahar–Varzaghan events. Several ground motions parameters, including PGA values and spectral acceleration, Fourier spectra, significant duration and Arias intensity obtained at two nearest stations (Siahoo and Varzaghan) in these two doublet events, are discussed. Comparison of spectral accelerations showed that the amplitude of spectral accelerations takes large values in short periods (high frequencies) at the Siahoo station. A large difference is observed between significant duration values obtained at Varzaghan and Siahoo stations which could be explained by the presence of a pulse in the records of Varzaghan station. The results also showed that the spectral level observed at the Sihao station in short periods is higher than the level of the seismic design code, which can be a reason for the high damage to low-rise buildings.