In mountain tunneling, it is important from the point of construction safety and effectiveness to obtain information on the weak zones such as fracture zone ahead of the face, which may pose problems during construction. To provide long-term outlook for tunnel work without disturbing excavation, the authors have developed a tunnel seismic reflection survey method known as the Taisei Blast Excavation Prospecting (T-BEP). This method extends the maximum surveyable distance beyond 350 m, doubling or tripling the capability of other conventional methods. However, complicated works are necessary in the preparation and measurement processes, and there are safety concerns. Therefore, we have improved the old T-BEP and developed a new version. In this paper, we present an overview of the new version and report the results of comparative validation experiments between the new and old T-BEPs.