Powerful 6.4 magnitude earthquake rattles Delhi, Gurgaon, Noida, and Nepal.
Tremors felt in Bihar and along the Indo-Nepal border.
Epicenter located in Nepal, near Ayodhya and Kathmandu.
Indian PM Modi expresses solidarity with Nepal, 128 lives lost.
Seismic event's grim toll: 140 injuries in Jajarkot and Rukum.
Delhi-NCR impacted, NCS reports depth of 10 km.
Third significant earthquake in Nepal within a month.