What can be the reason behind natural disestar?

Islamic history says about many generations/tribes/cities which were destroyed with natural disasters, as a punishment of their wrongdoings. Quran brought out various types of stories about theses. It pointed out that when people crossed their limits in wrongdoing, then Allah punished them with natural disasters, and the people who were righteous was rescued. Though it was never said that natural disaster won't happen in random. But it focused about a cause of natural disaster. (From my personal experience, I'd say, everything really happen for a purpose. But I do know only about my life, not about others not even about the whole world. As we fall sick sometimes and we don't care much about these just because we don't get time to think about these. But when I was sick during a critical(during my final) time and was so sick, even hospitalized for the first time and that made me thoughtful about the reason(I do want to mention that I felt like I was responsible for this, while I was facing various obstacles with life I had a lots of complains about these and used to say why don't I die! and the answer came just after one year later). And later on, 6 months ago I got into an accident, after that I got many advices, suggestions from well wisher to be careful about my movements, how I got into the accident! (but, cant help to say, that day when I was going outside I repeatedly was praying to Allah to protect me from an incident) And that day I broke my leg, first time serious accident in my life and had to stay home for few months. And it helped me from not to face the thing I was afraid of. So, was it an answer, wasn't these things were purposeful? PS: I do know about mine, not about others. Trust me, every wrong thing happened to me, I find a reason behind it that I should care about.) Today earthquake happened in my country in high scale. And in some other countries (ex-Nepal) many people died. My country is in high risk too. So, according to these thoughts, I was wondering, what is the actual reason behind natural disasters? I didn't know about any Islamic research on it. If there is any, what is the answer? Does disaster can happen just randomly or its an admonition from our creator? To the wrongdoers?