Impact assessment of the seasonal hydrological loading on geodetic movement and seismicity in Nepal Himalaya using GRACE and GNSS measurements

The Himalayan terrain is an epitome of ongoing convergence and geodetic deformation where both tectonic and non-tectonic forces prevail.In this study,the Gravity Recovery and Climate Experiment(GRACE)and Global Positioning System(GPS)datasets are used to assess the impact of seasonal loading on deformation with seismicity in Nepal.The recorded GPS data from 21 Global Navigation Satellite System(GNSS)stations during 2017-2020 are processed with respect to ITRF14 and the Indian reference frame,and the Center for Space Research(CSR)mascon RL06 during 2002-2020 is adopted to estimate the terrestrial water storage(TWS)change over the Ganga-Brahmaputra River basin.The results indicate that the hydrological loading effect or TWS change shows high negative,high positive,and moderately positive values in pre-monsoon,co-monsoon,and post-monsoon months,respectively.The detrended GPS data of both horizontal and vertical components correlate with the seasonal TWS change using the Pearson correlation coefficient at each GNSS site.In addition,the correlation coefficient has been interpolated using inverse distance weighting to investigate the regional TWS influence on geodetic displacement.In the north component,the correlation coefficient ranges from-0.6 to 0.6.At the same time,the TWS is positively correlated with geodetic displacement(0.82)in the east component,and the correlation coefficient is negative(-0.69)in the vertical component.The negative correlation signifies an inverse relationship between seasonal TWS variation and geodetic displacements.The strain rate is estimated,which shows higher negative values in pre-monsoon than in post-monsoon.Similarly,the effect of seismicity is 47.90%for pre-monsoon,15.97%for co-monsoon,and 17.56%for post-monsoon.Thus we can infer that the seismicity decreases with the increase of seasonal hydrological loading.Furthermore,the effect of strain is much higher in pre-monsoon than in post-monsoon since the impact of co-monsoon continues to persist on a small scale in the post-monsoon season.

Geodetic characterization of active Katrol Hill Fault(KHF)of Central Mainland Kachchh,western India

After the M7.7 earthquake in 2001,the Kachchh rift basin became the focus of various geological and geophysical researches on the western Indian plate.As an essential technology,the Global Navigation Satellite System(GNSS)has been utilized to study the deformation pattern in the central mainland Kachchh.We select the east-west striking Katrol Hill Fault(KHF)as the study area and analyze the crustal deformation pattern using the datasets from 2014 to 2019.The geodetic results along the KHF reveal a mean deformation of about 2.1 mm per year,which is higher in the eastern part and lower in the central and western parts.The investigation of deformation and derived strain reveals the segmented behavior of KHF,while the dominance of compressive strain(maximum 22 nanostrain/yr)in the eastern segment makes it the most active segment of the KHF.A higher deformation rate along the eastern KHF can be considered significant in terms of seismic hazard for this part of the Indian plate.