ARKHANGELSK, May 6. /TASS/. Russian scientists developed and patented a method to recognize local seismic events in the Arctic, head of the seismology laboratory at the Laverov Federal Research Center for Integrated Arctic Studies (the Urals Branch of the Russian Academy of Sciences), Corresponding Member of the Russian Academy of Sciences Galina Antonovskaya told TASS.
This method allows specialists to distinguish earthquakes from, for example, the destruction of ice domes, thus helping experts to predict iceberg formations.
"We have taken into account events, so-called volume waves on seismograms, to locate events and determine their locations. The corner frequency (angular frequency) is responsible for the focal zone size. The earthquake source is much bigger than the source of an ice event. We have also considered the frequencies accompanying these events. We've analyzed a big amount of data, split them into groups, identified patterns, and analyzed where exactly the event was located: on a fault zone or, for example, on the edge of a glacier. As a result, we have shown and proven these differences, which allowed us to obtain a patent," the expert said.
Highly sensitive sensors of seismic stations record events of different origin and magnitude. The equipment records fluctuations of the Earth's surface caused by both natural and man-made phenomena. However, in the Arctic, in addition to local events of man-made origin, such as open blasting operations in quarries and in construction of port facilities, ice domes and ice quakes are collapsing, which seismic sensors also can detect.
Seismologists may interpret recorded events in different ways. "Sensors record all incoming signals, and our task is to distinguish between them. To get an objective picture, we build up a time-spectral analysis by analyzing the spectra and frequencies at which these events are recorded. The resulting diagrams show characteristic features. For example, industrial explosions are accompanied by monochrome stripes, which allows us to identify such types of signals as man-made, since natural events look different on diagrams," the laboratory's leading researcher Yana Konechnaya said.
Difference between earth and ice quakes
The center's scientists have developed methods to distinguish between ice and seismic events based on statistical data obtained from a single station installed in the Severnaya Zemlya Archipelago's ground, rather than on ice.
According to Antonovskaya, when developing the methods, specialists eyed spectral-temporal diagrams (Swan diagrams) of recorded events, their angular frequencies, and used statistical methods to split events into two types: a local earthquake and an ice quake.
This methodology has been applied to events recorded on the Franz Josef Land Archipelago, where scientists have obtained a big amount of data indicating that only ice quakes are recorded around 50 km from the seismic station, while earthquakes occur much further away - at a distance of about 150-200 km.
The glaciers destruction is an urgent problem for the polar regions. These processes may cause dangerous situations and hinder navigation in the Arctic Ocean seas, and the operation of the Northern Sea Route. The obtained methods may be used in forecasting iceberg formations.