Regional variation of the ω-upper bound magnitude of GIII distribution in Hindukush-Pamir Himalaya and the adjacent regions: A perspective on earthquake hazard

Abstract

The upper bound magnitude (ω) or maximum magnitude in 28 seismogenic source zones in the Hindukush-Pamir Himalaya and the adjacent regions have been computed with the help of a complete and homogeneous earthquake catalogue during the period 1900–2010 to estimate the earthquake hazards in the region. The Gumbel's third asymptotic distribution (GIII) of extreme value method is used to estimate this parameter. In this study, a comparison of maximum magnitude obtained by GIII distribution is carried out with Kijko–Sellevoll method. It is observed that the maximum earthquake magnitudes estimated by Kijko–Sellevoll and GIII methods are comparable to each other and the average of differences of their values is only 0.13. The results also estimate the most probable earthquake magnitude that can be expected in next 100years (M100) in all 28 seismogenic source zones. An effort is made to make regression relations between ω and maximum magnitude estimated by Kijko–Sellevoll method (Mmax(KS)) and ω and maximum observed magnitude (Mmaxobs). The estimated ω values exceeded the value of 7.00 in 15 and 8.00 in 5 of the 28 seismogenic source zones. The geographical distribution of ω and M100 in 28 seismogenic source zones of the study region is visualized to analyze the localized seismicity parameters. It is observed that earthquake hazard level varies spatially from one zone to another, which suggests that examined region have high crustal heterogeneity and seismotectonic complexity.