The first known earth in Nepal was the earthquake of 1255 A. D.It has destroyed many houses and temples and killing one third to one fourth population of the Kathmandu Valley. According to book (Chitrakar and Pandey, 1986) The assigned intensity was about X in MM scale.
1310 BS / 1255 AD The first recorded earthquake in history of Nepal took place on June 7, 1255 AD. One third of the total population of Kathmandu were killed including Abahya Malla , the King of Kathmandu valley , numerous buildings and temples of the valley were entirely destroyed while many of them were severely damaged, the magnitude of the earthquake is said to be around 7.7 in Richter scale.
Similarly in the years of 1408 A.D, 1681 A.D. and 1810 A.D. massive earthquake struck Nepal destroying many houses and killing many life’s. However intensity of those quakes were not known.
In the years 1833 A. D. (R.Bilham,1995) another earthquake devastated Kathmandu valley. Its magnitude was reported to be of Mb=7.8 with possible rupture length of more than 70 km and the event was located at 50 km North – North East of Kathmandu.
The earthquake of 1934 A. D.( Which is also known as The Great earthquake of 90) was the most devastating earthquake ever occurred in the territory of Nepal with casualties of more than 16000 people including from Nepal and India put together. The rupture length is estimated to be 200 Km 100 Km (Molnar and Pandey, 1994). This 8.0 magnitude earthquake occurred on 15 January at around 2:00 PM (N.S.T.) and caused widespread damage in northern Bihar and in Nepal.
2045BS/1988AD Udayapur Earthquake, Eastern Development Region mostly affected and some parts of Central Development region affected, 721 deaths, 6553 people injured, 64174 private buildings, 468 public houses, 790 government buildings damaged, 1566 live stocks, 22 districts of eastern Nepal affected.
The April 2015 Nepal earthquake (also known as the Gorkha earthquake) killed more than 8,800 people and injured more than 23,000. It occurred at 11:56 NST on 25 April, with a magnitude of 7.8 on rector scale and a maximum Mercalli Intensity of IX (Violent). Its epicenter was east of the district of Lamjung, and its depth was of approximately 15 km (9.3 mi).It was the worst earthquake in Nepal since the 1934 Nepal–Bihar earthquake.
The earthquake also triggered an avalanche on Mount Everest, killing at least 19, making April 25, 2015 the deadliest day on the mountain in history.The earthquake triggered another huge avalanche in the Langtang valley, where 250 people were reported missing.
Wiki, Seismonepal, Sheetal Subedi and Tilottam Paudel