Regional adjustment factors for three NGA-West2 ground-motion prediction equations to be applicable in northern Iran

Ground-motion prediction equations (GMPEs) are essential tools in seismic hazard studies to estimate ground motions generated by potential seismic sources. Global GMPEs which are based on well-compiled global strong-motion databanks, have certain advantages over local GMPEs, including more sophisticated parameters in terms of distance, faulting style, and site classification but cannot guarantee the local/region-specific propagation characteristics of shear wave (e.g., geometric spreading behavior, quality factor) for different seismic regions at larger distances (beyond about 80 km). Here, strong-motion records of northern Iran have been used to estimate the propagation characteristics of shear wave and determine the region-specific adjustment parameters for three of the NGA-West2 GMPEs to be applicable in northern Iran. The dataset consists of 260 three-component records from 28 earthquakes, recorded at 139 stations, with moment magnitudes between 4.9 and 7.4, horizontal distance to the surface projection of the rupture (R _JB) less than 200 km, and average shear-wave velocity over the top 30 m of the subsurface (V _S30) between 155 and 1500 m/s. The paper also presents the ranking results for three of the NGA-West2 GMPEs against strong motions recorded in northern Iran, before and after adjustment for region-dependent attenuation characteristics. The ranking is based on the likelihood and log-likelihood methods (LH and LLH) proposed by Scherbaum et al. (Bull Seismol Soc Am 94: 2164–2185, 2004, Bull Seismol Soc Am 99, 3234–3247, 2009, respectively), the Nash–Sutcliffe model efficiency coefficient (Nash and Sutcliffe, J Hydrol 10:282–290, 1970), and the EDR method of Kale and Akkar (Bull Seismol Soc Am 103:1069–1084, 2012). The best-fitting models over the whole frequency range are the ASK14 and BSSA14 models. Taking into account that the models’ performances were boosted after applying the adjustment factors, at least moderate regional variation of ground motions is highlighted. The regional adjustment based on the Iranian database reveals an upward trend (indicated as high Q factor) for the selected database. Further investigation to determine adjustment factors based on a much richer database of the Iranian strong-motion records is of utmost important for seismic hazard and risk analysis studies in northern Iran, containing major cities including the capital city of Tehran.     

Investigation of elemental enrichment and ecological risk assessment of surface soils in two industrial port cities,southwest Iran

In recent years, there has been a rapid growth in the two industrial port cities of Iran, the port of Mahshahr and the port of Imam Khomeini. In spite of their importance for the economy, the two cities require monitoring and assessment from an environmental and human health perspective. In this study, environmental quality and heavy metals pollution of soils influenced by human activities were investigated. A total of 30 soil samples were collected and subjected to detail physicochemical characterization. The results showed high levels of heavy metals in the urban soils of port of Mahshahr (POM) and elevated respective levels in surface soils of the port of Imam Khomeini (PIK) with Ni being significantly higher than those in POM. The integrated pollution index (IPI) values of metals ranged from 1.22 to 1.87 in POM and 1.52 to 3.31in PIK, 50% of soil samples in PIK were classified as highly polluted, and all of the soil samples in PM were classified as moderately polluted. These results are in accordance with Enrichment Factor (EF) values, which showed the role of anthropogenic activities in the soil heavy metal enrichment. Moreover, the highest potential ecological risk index (RI) was found in the sites of petrochemical industries in PIK indicating serious metal contamination. Statistical analysis showed that heavy metals were mainly controlled by human activities. The results showed more dense industrial activity in PIK is responsible for higher pollution. This study establishes a benchmark against which future monitoring and remediation programs can be based on. Because of proximity to the Persian Gulf, continued the release of contaminants into the region, could have adverse biological health effects.