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Inferred Peak Ground Acceleration (PGA) Created by: ImageCat, Inc. Point(s) of Contact: Charles K. Huyck, http://imagecatinc.com Region: Greater Kathmandu area Date: 2015-04-25 Generated: 2015-05-11 |
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Description: The April 25th 7.8 Gorkha earthquake in Nepal occurred in an area with very few seismic stations. Ground motions were estimated primarily by Ground Motion Prediction Equations (GMPEs) over a very large region, with a very high degree of uncertainty. Accordingly, initial fatality estimates and their distribution was highly uncertain, with a 65% chance of fatalities ranging from 1,000 to 100,000. With an aim to developing estimates of: 1) the number of buildings damaged by category (slight, moderate, extensive, complete), 2) fatalities and their distribution, and 3) rebuilding costs, researchers at ImageCat have developed a preliminary inferred Peak Ground Acceleration product in %g (PGA). The inferred PGA is determined by using observations of building collapse from the National Geospatial Agency and building exposure estimates to determine the percentage of buildings collapsed in key locations. The percentage of building collapse is adjusted for accuracy and cross referenced with composite building damage functions for 4 development patterns in Nepal: 1) sparsely populated, 2) rural, 3) dense development, and 4) urban development to yield an inferred PGA. Composite damage functions are derived from USGS Pager collapse fragility functions (Jaiswal et al., 2011) and are weighted by building type frequencies developed by ImageCat. The PGA is interpolated to yield a surface. An initial estimate of the fatalities based on ATC 13 (Rojan and Sharpe, 1985) using these PGA yields an estimate of 15,758. The inferred PGA product is recommended for use solely in loss estimation processes. Data Source(s):Jaiswal, K., Wald, D., & D'Ayala, D. (2011). Developing empirical collapse fragility functions for global building types. Earthquake Spectra, 27(3), 775-795. NGA (2015) All Damage Nepal May 3rd 2015 Points, shapefile. Retrieved from https://ngamaps.geointapps.org/arcgis/rest/services/NEPAL/Latest_NGA_Damage_Assessment_Centroid/MapServer Rojahn, C. and Sharpe, R.L. (1985). "Earthquake damage evaluation data for California". Report No. ATC-13, Applied Technology Council, California. Trifunac, M.D., 1976. "A Note on the Range of Peak Amplitudes of Recorded Accelerations, Velocities, and Displacements with Respect to the Modified Mercalli Intensity Scale," Earthquake Notes, vol. 47, no. 1. Building exposure database and analysis credit: ImageCat Link: TIF TIF (Legend) KML More Information: For more information about this product, visit: ImageCat |
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