8 causes of Earthquake - Maha-parinibbana Sutta Buddha as part of the noble eightfold path preached that killing any organism is an unskillful action which results in bad karma. He also preached that every buddhist monk's final aim should be nibbana. In the Maha-parinibbana Sutta, it's mentioned that one cause for earthquake is a monk attaining enlightenment. Earthquakes result in the killing of atleast few organisms. So that should mean a monk should not pursue enlightenment. How does a practicing buddhist monk address this apparent contradiction?

Thanks.
There are instances where the earth trembled due to certain significant event or a very meritorious person. But I do not think these are not very serious tremors. In recent times also these have happened. E.g.

Sometimes, even in this unhappy atmosphere, there would be a ray of hope. Sayagyi had said that on my arrival in India, nature would give a sign of my future success. I travelled by air from Yangon (Rangoon) and, as it happened, when I descended from the plane in Calcutta there was an earth tremor. The next day I read in the newspapers that it had affected a large area of northern India. To me it was as if the country was thrilled to regain the long-lost jewel of the Dhamma.
Signs of this kind had occurred in the time of the Buddha. Was this nature’s way of expressing joy at the rebirth of the Buddha’s teaching through the return of Vipassana? However, when I recalled the present difficulties, I felt that perhaps the earthquake had just been a coincidence and that it was senseless to give it importance. I needed to understand and accept the existing situation, which was bleak.

Source: First Vipassana Course In India
Killing many beings who a meritorious may cause natural disasters. In the past there is a Tsunami which hit Sri Lanka when an Arahat was killed. In such cases life may get harmed.
Being enlightened is beneficial to oneself and others. Generally as far as I know earth tremors arising from this do not harm beings.