• Aamir Ali

      Articles written in Journal of Earth System Science

    • Spatio-temporal variations of b-value in and around north Pakistan

      Khaista Rehman Asghar Ali Sajjad Ahmed Wajid Ali Aamir Ali Muhammad Younis Khan

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      The seismotectonic structure of north Pakistan has been formed by ongoing collision between the Eurasian and Indian plates. North Pakistan and the adjoining areas experienced many large earthquakes in the past, which resulted in considerable damages and loss of life. A magnitude-homogenous earth-quake catalogue for north Pakistan and its surrounding areas for the instrumental period from 1964 to 2007 is used for analysis. We presented seismicity picture of the Hindukush–Pamir–Karakoram (HPK), Kohistan Island Arc (KIA) and Hazara–Kashmir–Himalayas (HKH) using various histograms and time series plots of the dataset. The b-value for each accreted domain is derived separately and investigated through a process of mutual correlation. Our computed temporal variation of b-value in Hazara region shows a significant decrease prior to 2005 Kashmir earthquake.

    • Bayesian inversion of synthetic AVO data to assess fluid and shale content in sand-shale media

      Hafiz Mubbasher Anwer Aamir Ali Tiago M Alves

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      Reservoir characterization of sand-shale sequences has always challenged geoscientists due to the presence of anisotropy in the form of shale lenses or shale layers. Water saturation and volume of shale are among the fundamental reservoir properties of interest for sand-shale intervals, and relate to the amount of fluid content and accumulating potentials of such media. This paper suggests an integrated workflow using synthetic data for the characterization of shaley-sand media based on anisotropic rock physics (T-matrix approximation) and seismic reflectivity modelling. A Bayesian inversion scheme for estimating reservoir parameters from amplitude vs. offset (AVO) data was used to obtain the information about uncertainties as well as their most likely values. The results from our workflow give reliable estimates of water saturation from AVO data at small uncertainties, provided background sand porosity values and isotropic overburden properties are known. For volume of shale, the proposed workflow provides reasonable estimates even when larger uncertainties are present in AVO data.

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