Estimation and Validation of Arias Intensity Relation Using the 1991 Uttarkashi and 1999 Chamoli Earthquakes Data

Arias intensity is one of the most crucial ground motion parameters to estimate the amplitude, frequency and ground shaking duration content. In the present work, we have estimated Arias intensity for the Garhwal Himalaya, India using: (1) strong motion data of the 1991 Uttarkashi earthquake and the 1999 Chamoli earthquake and (2) available empirical relations. Further, these results are compared at several stations, and a close resemblance of estimated Arias intensity from the recorded data and empirical relations is observed, which validates the empirical relation for the present study region. Furthermore, the study region (30.0°N – 31.0°N; 78.6°E – 79.6°E) is divided into 100 small grids, and the Arias intensity values are computed at each grid. These values calculated at each corner of the grid are further utilized to prepare the contour maps of Arias intensity for the Garhwal Himalaya, India for the 1991 Uttarkashi (Mw 6.8) and the 1999 Chamoli (Mw 6.6) earthquakes. The Arias intensity maps are also prepared for the future scenario of earthquakes of magnitude Mw 8.5, keeping the rupture location at the epicentre of the Uttarkashi and Chamoli earthquakes. The Arias intensity maps reveal that 51% and 45% of the area consist of ˃ 0.11 m/s Arias intensity susceptible to landslide corresponding to the Uttarkashi and Chamoli earthquakes, respectively. Hence, the obtained Arias intensity is revealed to be a trustworthy parameter to define earthquake shaking essential to generate landslides.