Exploration
Rashed Pourmirzaee; Hadi Jamshid Moghaddam
Abstract
In recent years, hyperspectral data have been widely used in earth sciences because these data provide accurate spectral information of the earth's surface. This research aims to apply match filtering (MF) on Hyperion hyperspectral imagery for mapping alteration mineral in the Astarghan area, NW Iran. ...
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In recent years, hyperspectral data have been widely used in earth sciences because these data provide accurate spectral information of the earth's surface. This research aims to apply match filtering (MF) on Hyperion hyperspectral imagery for mapping alteration mineral in the Astarghan area, NW Iran. Astarghan is located in the northwest of Iran where deposits of low-sulfide gold-bearing ore rocks occur as veins and stockworks. Therefore, at first, the Astarghan Hyperion scene was topographically and atmospherically corrected. Then, the data quality was surveyed to recognize bad bands and improve the accuracy of the subsequent processing steps. In MF analysis, it is a challenge to separate MF abundance images to target and background pixels. Therefore, to cope with this challenge, a moving threshold technique is proposed. The results indicated three indicative minerals including kaolinite, opal and jarosite. Then, the results were statistically verified by virtual verification and geological data. The verification was performed virtually using United States Geological Survey (USGS) spectral library data, which showed an agreement of 78.06%. Moreover, a comparison of the MF analysis results showed a good agreement with field investigations and overlaying with a detailed geological map of the study area. Finally, in this study the X-ray diffraction (XRD) of three indicative mineral samples was used to check the efficiency of the applied method.
A. Zarean; R. Poormirzaee
Abstract
Shear-wave velocity ( ) is an important parameter used for site characterization in geotechnical engineering. However, dispersion curve inversion is challenging for most inversion methods due to its high non-linearity and mix-determined trait. In order to overcome these problems, in this study, a joint ...
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Shear-wave velocity ( ) is an important parameter used for site characterization in geotechnical engineering. However, dispersion curve inversion is challenging for most inversion methods due to its high non-linearity and mix-determined trait. In order to overcome these problems, in this study, a joint inversion strategy is proposed based on the particle swarm optimization (PSO) algorithm. The seismic data considered for designing the objects are the Rayleigh wave dispersion curve and seismic refraction travel time. For joint inversion, the objective functions are combined into a single function. The proposed algorithm is tested on two synthetic datasets, and also on an experimental dataset. The synthetic models demonstrate that the joint inversion of Rayleigh wave and travel time return a more accurate estimation of VS in comparison with the single inversion Rayleigh wave dispersion curves. To prove the applicability of the proposed method, we apply it in a sample site in the city of Tabriz located in the NW of Iran. For a real dataset, we use refraction microtremor (ReMi) as a passive method for getting the Rayleigh wave dispersion curves. Using the PSO joint inversion, a three-layer subsurface model was delineated.The results obtained for the synthetic datasets and field dataset show that the proposed joint inversion method significantly reduces the uncertainties in the inverted models, and improves the revelation of boundaries.
