Seismicity Analysis of Nepal Himalaya

Abstract

The high occurrence of seismic activity in the Nepal Himalaya is primarily a result of the ongoing collision between the Indian continental plate and the Eurasian continental plate. This study focuses on estimating and analyzing the source parameters of earthquakes in the Nepal Himalaya region. The study area, situated in the eastern part of Nepal Himalaya, encompasses the central portion of the Himalayan range. Various tectonic features within the study area, such as the Main Central thrust (MCT) and Main Boundary Thrust (MBT), have been identified and mapped. In this study local seismicity of Nepal Himalaya based on the past data is also discussed. The spatial and temporal distribution of past earthquake data is discussed which shows incompleteness in database for medium magnitude earthquake from 1801-1963. The distribution of earthquakes over time is examined and divided into distinct time periods, including earthquakes that occurred before 1800, those between 1801 and 1963, and those between 1964 and 2015. The characteristics of an earthquake source can be gleaned from its source parameters, which include stress drop, corner frequency, and seismic moment. These parameters are valuable for estimating the intensity of ground motion during earthquakes. In this study, the source parameters of over 100 local events (with magnitudes ranging from 0.1 to 4.2) were estimated using the digital time histories that were available. Using Brune’s model corner frequency and low frequency asymptote are estimated from the spectral method which helps in estimating different source parameters. Between November 2019 and August 2020, the seismographs have recorded 522 events among them only 363 events are located. The events were recorded by a network of digital seismographs. These seismographs are consisted of Triaxial Seismometer and Broadband Triaxial Seismometer. These seismographs were deployed at six stations in the Lesser Himalaya.