Scientists have explained the mechanism of occurrence of unusual earthquakes that occur at a depth of more than 40 km below the earth’s surface. A study by geologists from the University of Plymouth is published in the scientific publication Nature Communications. In addition, they released a large documentary called Pseudo Tachiliter.
Despite the unusual and almost unexplored mechanisms of the occurrence of these types of deep-seated earthquakes, they account for up to 30% of inland seismic activity. For example, the Bhuj earthquake in 2001 in India, as well as almost all seismic activity in the Himalayas, are associated with these processes.
An international group of scientists led by Professor Heidi Morstang from the University of Plymouth, in his study, came to the conclusion that such processes can be caused by the interaction of various zones of masses moving deep underground. This happens extremely slowly, however, these processes load neighboring blocks of hard rocks in the deep crust. As a result, they do not withstand this pressure, and powerful earthquakes occur.
Although earthquakes are only a temporary component of such seismic deformation cycles, they release a significant fraction of the stored energy in regions with slowly moving rock masses.
As part of the research, geologists studied the lower crust of the Lofoten Islands, since this region is one of the few areas of the Earth with exhumed bark. This layer is covered with pseudotachilites – hardened rock, which is considered the result of seismic activity of underground rocks.
“Lofoten Islands provide a unique place to study the effects of earthquakes in the lower crust. But if you look at sections of open rock with a width of more than 15 m, we will see examples of slowly forming deformation of the rock. It causes earthquakes that occur at a depth of up to 30 km. The model we developed provides a new explanation of the causes and consequences of such earthquakes in many places where this happens”.
Lucy Campbell, Researcher at Plymouth University
As part of the study, director of the University of Plymouth, Heidi Morstang, created a 60-minute documentary called Pseudotachilite, about the process of exploring these regions. The film premiered at the International Film Festival in Bergen in 2019.