جستجوی مقالات مرتبط با کلیدواژه « seismic hazard assessment » در نشریات گروه « زمین شناسی »

In the present study, probabilistic seismic hazard assessment (PSHA) and disaggregation of seismic hazard in Golestan and adjacent areas have been conducted. The study area includes Golestan province and surrounding areas to about 150 km away from the geographical borders of the province. For this purpose, at the first stage, geological and seismotectonic studies, including the tectonic features, faults dimensions, and faults mechanism in the study area have been studied. The seismicity parameters including b-value, annual mean occurrence rate (λ) and maximum possible magnitude (Mmax) of the study area are evaluated based on the uniform catalog containing historical and instrumental earthquakes from 400 BC to the end of 2021 AD with magnitudes ranging from 3.5 to 7.5 on the Mw scale. Based on the geological and seismological information of the study area, 21 areal seismic source zones have been identified. Using the spatial distribution function, the annual mean occurrence rate of earthquakes of each seismic source has been determined in different magnitude intervals. The latest three local ground motion prediction equation models of the Iranian plateau, have been employed to assess the peak ground acceleration (PGA) and spectral acceleration (SA) in periods of 0.2, 1, and 2 seconds for return periods of 50, 475 and 2475 years. A three branches logic tree with the same weight has been used to apply the GMPEs. The GMPEs are specific to Iran and used for the first time in the study area. The entire study area is divided into points that are 5 km apart. Subsequently, the PGA and SA have been calculated for each point with the OpenQuake software package. The results are presented in the form of seismic hazard zoning maps in Golestan province and spectral acceleration curves for Gorgan city. The calculations are on the bedrock site condition according to the Iranian code of practice for seismic resistant design on building (Standard No. 2800 4th edition). In order to determine the most effective seismic source in the PGA of the Gorgan, the disaggregation of PSHA has been conducted on the parameters of distance, magnitude, the number of standard deviations (ε), and latitude and longitude. The most probable scenario of maximum acceleration in Gorgan has been introduced. The results show that some areas of the Gorgan, Kord-Kouy, Agh-Ghala and Ali-Abad in southwest and Maraveh-Tapeh in northeast of the province can be affected by more ground acceleration than other areas so that the maximum ground acceleration in these areas for the return period of 475 years is 0.21g to 0.25g. The disaggregation of PSHA for Gorgan city shows that the Caspian and North Alborz faults have the most substantial contribution in the PGAs of Gorgan.

In this study, we used the recent comprehensive earthquake catalogue of Mousavi-Bafrouei and Babaie Mahani (2020), including historical and instrumental earthquakes until the end of 2018, to calculate Probabilistic Seismic Hazard Assessment (PSHA) at eight metropolitans with a population of more than 1 million. These metropolitans include Ahvaz, Isfahan, Karaj, Mashhad, Qom, Shiraz, Tabriz, and Tehran. Our approach was implemented using a MATLAB code that was compiled for the purpose of this study. The historical seismicity within a 300-km radius was considered around each city, and the seismicity parameters were obtained in each case. We provided the hazard curve and uniform hazard spectrum for peak ground acceleration (PGA) and pseudo-response spectral acceleration (PSA) at periods of 0.04, 0.1, 0.2, 0.3, 1.0, and 3.0 sec for the return periods of 50, 475, and 2475 years, respectively. For hazard calculations, we used four ground motion prediction equations with equal weights; Boor et al. (2014), Idriss (2014), Kale et al. (2015), and Farajpour et al. (2019). Our PSHA results show that the highest hazard occurs in the cities of Shiraz and Tabriz, whereas the lowest hazard level happens in the city of Isfahan. Specifically, the largest PGA values at the bedrock ( = 760 m/sec) condition and for the return periods of 50, 475, and 2475 years are 77 cm/sec2 (Shiraz and Tabriz), 203 cm/sec2 (Shiraz and Tabriz), and 535 cm/sec2 (Tabriz), respectively. On the other hand, the smallest PGA values for the same return periods occur for the city of Isfahan at 29 cm/sec2, 77 cm/sec2, and 125 cm/sec2. We also compared our results with other PSHA studies obtained by other researchers, including Mousavi Befrouei et al. (2014), Salahshour et al. (2018), and Shahbazi and Mansouri (2019). In general, we found that our results show lower values in terms of ground motion amplitudes. For example, Mousavi-Bafrouei et al. (1393) obtained higher values by up to ~30% than those obtained in this study. This difference is probably due to the inclusion of different datasets for source characterization and calculation of seismicity parameters. In the approach used in this study and the works of Salahshour et al. (2018) and Shahbazi and Mansouri (2019), historical seismicity is the only source of information for the determination of seismic sources and their parameters, which resulted in similar ground motion values. However, Mousavi Befroui et al. (2014) used geological, geophysical, and seismotectonic evidence along with historical seismicity for source characterization.