Delhi comes under seismic zone 4.Even a small tremor can make much damages in Delhi. In 1960 4.8 riktar scale earthquake in Delhi-Gurgaon circle made cracks in few buildings but not any catastrophic damages.Delhi is densely populated city.There is always risks of major damages.About 3 major faults will be responsible for earthquake in Delhi.Faults means interactions or junction where tectonic plates meet.