ABSTRACT - The online social media networks have become an important source for detecting real-world happenings in this modern digital world. Event detection has become an essential research topic nowadays because it illustrates different scenarios during crisis or events as it contains significant information about them. Several approaches exist for detecting and analyzing events which provide valuable information for various applications like disaster and crisis management, detecting disease outbreak, health monitoring, traffic management and opinion mining. Traditional event detection methods that are proposed for handling large, formal and structured documents are not suitable for social media networks due to its unique characteristics such as restricted length, unstructured phrases, time sensitivity and massive information. This article provides a survey of methods used for detecting event in online social media and also gives an outline of challenges that are faced in handling social media post.