EARTHQUAKE SURFACE FAULT RUPTURES AND THEIR INVESTIGATIONS

Abstract

Surface fault ruptures occur during very strong earthquakes with rather shallow hypocentres. They are primary earthquake effects, because they are the surface manifestation of the slip of two tectonic blocks, which for most earthquakes occur only at depth. They are characteristic of areas of the world with large tectonic deformations, such as Turkey, California, Taiwan and New Zealand. The largest fault ruptures are several tens of kilometres long with displacements of up to several metres, and can severely damage buildings, roads, railways and embankments. For critical infrastructure such as nuclear power plants, water dams and oil pipelines, the damage or collapse of which would produce catastrophic secondary effects, it is mandatory to demonstrate, through extensive investigations, that the danger of surface rupture is negligible. Surface ruptures are studied by geological, geomorphological, geodetic and geophysical methods. Among them, remote sensing methods, such as satellite radar interferometry and airborne laser scanning methods, have made the greatest progress in the past few decades. In Slovenia no earthquake surface rupture associated with a documented earthquake has yet been proven, although it has very likely occurred in the largest historical earthquakes. For this reason all necessary investigations are being carried out for critical infrastructure. Near Slovenia, an earthquake occurred in Petrinja (Croatia) in December 2020 with surface rupture displacements of up to 0.5 m.