Transportation networks, with tunnels as their integral parts, are considered to be of paramount importance when the risk under strong earthquakes is considered. Namely, accessibility of roads affects the speed and the scope of the emergency measures to be provided in the very immediate postearthquake emergency and relief operations. In addition, the seismically induced damage to the infrastructure could severely affect the economy of a region due to the time required to restore the functionality of the network. Moreover, underground structures are quite often located under densely populated urban areas. Considering all the former facts, these structures require very high standards in terms of their stability and safety.

In this respect, the paper is dealing with an overview of the current state of achievements in the area of seismic design codes for underground facilities, with an aim to point out to that nowadays, in spite of a significant step forward in the scientific–research work concerning seismic analysis of tunnels over the past decade or two, yet, even in the most developed countries, there still exists a lack of systematic and precisely established seismic design rules for tunnels and underground structures, which are of huge importance.