Seismic retrofit Seismic retrofit Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries (US, Japan etc.) and late 1970s for many other parts of the world (Turkey, China etc.), many structures were designed without adequate detailing and reinforcement for seismic protection. In view of the
Seismic source are efficient seismic sources because of their reduced costs, ease of transport in difficult terrains, and lack of regular maintenance compared to other sources,the use of explosives is becoming restricted in certain areas, causing decline and increasing popularity for alternative seismic sources. For instance, hexanitrostilbene was the main explosive fill in the "thumper" mortar round canisters used as part of the Apollo Lunar Active Seismic Experiments. Generally, the explosive charges are placed between below ground, in a hole that is drilled with dedicated drilling equipment for this purpose. This type of seismic drilling is often referred to as "Shot Hole