Estimation of Seismicity Parameters for the Updated Catalog of Tapovan, Uttarakhand

An updated catalog is prepared for Tapovan, Uttarakhand, considering the historical and instrumental data of the region. As per the Indian seismic code IS 1893, it lies in Zone IV (severe) and Zone V (very severe). Due to the fast-growing infrastructural facilities coming up in this region and the high seismicity, it is necessary to prepare an updated catalog for this region which will help in seismic hazard assessment. The seismic study area is selected as 500 km with Tapovan as the center having coordinates 30.5578° N and 79.5592° E. The historical and instrumental earthquake data were collected from different sources, and a homogenized catalog of 17,718 events was prepared using different conversion relations. Declustering of the data was done to eliminate the dependent events which will give better accuracy in estimating the return period. Zmap program was used for the declustering and 9429 events were obtained. A seismotectonic map was prepared considering the earthquake data, active faults, and lineaments. The completeness of the earthquake data was done using the Stepp method, and it was found that higher magnitude earthquakes had a larger completeness period. The seismicity parameters were estimated using Gutenberg–Richter (G-R) recurrence law, and the “a” and “b” values were found to be 6.257 and 1.0208, respectively. Kijko’s MATLAB algorithm was used to determine the maximum magnitude of the earthquake for the region and the value obtained was 8.52 which is considered high. This study estimates seismicity parameters for the hazard studies by considering the updated catalog till the year 2022.