Abstract: The 2023 local magnitude (M_L) 6.4 Jajarkot earthquake was the most destructive event to occur in the source region of the 1505 M_W8.2 Lo Mangthang Mustang earthquake in western Nepal. Here we used local seismic stations deployed in Nepal and southern China, and teleseismic stations with depth phase records to study the earthquake relocation and source rupture process. The Jajarkot earthquake was relocated to an epicenter at 28.828°N, 82.110°E and a focal depth of 13 km. The fault plane solution showed a thrust fault earthquake with a north-dipping angle of 21°. The released seismic moment was 3.88 × 10¹⁷ N·m, corresponding to a moment magnitude (M_W) of 5.7. The rupture area was 25 km along the strike and 20 km along the dip. The rupture nucleated on the ramp structure of the main Himalayan thrust and propagated to shallower depths, causing severe damage to the surrounding region. This study provides new insights into the local geometry of the main Himalayan thrust within the seismic gap zone in western Nepal.