Seismic gap have occurred in previously-identified seismic gaps. Prior to the 1989 Loma Prieta earthquake, that segment of the San Andreas fault system recorded much less seismic activity than other parts of the fault. The main shock and aftershocks of the 1989 event occurred within the previous seismic gap. Immediately following the 2004 Indian Ocean earthquake, a seismic gap analysis of the seismic zones around the Pacific Ocean identified the Central Kuril segment of the Kuril-Kamchatka Trench subduction zone as the most likely to give rise to a major earthquake. This zone, 500 km in length, at that time had experienced no
Seismic risk condition. Acquiring and analyzing the specific data for an individual building or facility is one of the most expensive and daunting aspects of seismic risk estimation. Progress is made if one can calculate the 'fragility' or seismic capacity of the components within a structure. In 1999, ASTM produced guidelines for reporting seismic loss estimates on commercial properties, commonly known as Probable Maximum Loss or PML reviews. These guidelines specify the scope of work, qualifications of the reviewer, and proper nomenclature for reporting loss estimates. Seismic risk can be reduced by active programs that improve emergency response, and improve basic infrastructure.