-
Osservatorio Sismologico MZS
Programma Nazionale di Ricerche in Antartide
The Very-Broadband Seismographic Observatory at Terra Nova Bay (TNB) was installed during the 1988-89 Campaign, and has been operating since then.
The seismological station is composed of state-of-the-art equipment, that is: very broad band high dynamics seismometers, high resolution advanced 24 bit data loggers, accurate GPS timing, and some workstations for auxiliary acquisition and data analysis.
The regular operation of the Observatory consists of unmanned, continuous recording of seismometric data. During summer, engineers carry out maintenance and upgrading of all instrumentation.
It is possible to dial up the station, all year long, for data retrieval and monitoring of the state of the health of all the equipment. We are looking forward to get availability of a permanent Internet access, in order to transmit data worldwide in real time.
A similar observatory is in operation at Concordia Station, Dome C. Here, we have excavated a vault in the ice, at a depth of 12 meters below the snow surface, in order to achieve the best coupling with the sensors (compact ice), and a very stable environment, particularly for temperature. At the surface there is a shelter containing data loggers, communication equipment, and power supply. The seismic station works continuously and permanently, thanks to the st winter-over opening of Concordia Station. Both seismographic observatories are part of the global federative network FDSN.
In addition, we also periodically carry out studies of microseismicity next to TNB, by means of temporary surveys. In the last years, we conducted a number of seismological campaigns in the area of the David Glacier, Victoria Land, in cooperation with researchers of Geological and Nuclear Sciences (Lower Hutt, NZ), and we are planning to carry out new experiments. The portable network equipment is composed of 9-12 portable seismological stations, powered by solar cells and batteries.
All activities follow the recommendations of IASPEI (Int. Ass. of Seismology and Physics of the Earth's Interior) through the Federation of Digital Seismographic Networks (FDSN). In Italy, all data recorded are analysed, validated, and distributed following international standards and protocols. As mentioned above, modern satellite communication technology will be used in the near future to achieve remote control of the equipment, and data telemetry, in order to reach the best performance for remote, unmanned observatories.
A real advancement of the knowledge of Earth structure and earthquake source mechanisms can only be achieved through an improved global coverage using state-of-the-art seismographs. The distribution of seismographic stations is still far from optimal: the southern hemisphere is very irregularly covered, and Antarctica is almost completely devoid of modern instrumentation. This is particularly limiting, for instance, for studies of the properties of the inner core of the Earth, which are latitudinally dependent (axial anisotropy and possible differential rotation of inner core and mantle) and therefore require more observations positioned at high latitude. These are the main reasons why Antarctica represents an observation point of special interest to global seismology, and seismograms there recorded have particular value. Antarctica is also a continent largely unknown to Earth Sciences, and seismological data are essential to solve the apparent geodynamic paradox we face today: surrounded by spreading ridges (which would induce compressive stresses) the continent is instead marked by a great rift structure, and it is characterized by a scarce, largely unknown, seismicity.
Microseismicity of the Antarctic continent is very little known, and the relation between glacial dynamics and tectonics is not yet well understood. Following the recommendations of the SCAR Group of Specialists on Antarctic Neotectonics (ANTEC) we are carrying out these studies by means of two other field installations of the temporary network, to gather further data to complement those given by permanent observatories (TNB, Scott, Dry Valleys) and those already recorded in the field (our 2003-4 experiment, the American TAMSEIS campaign ending in one year) in order to better determine focal depths, focal mechanisms, and crustal structure. Because of its position in the interior of the Antarctic continent, in a wide area devoid of seismographic instrumentation, Dome C also represents an extremely important vantage point for seismology. Its distance from the sea and wave-induced disturbance makes Dome C a potentially very quiet site. Its distance from other stations make its interest high for global seismological studies, for determination of continental lithospheric structure, and for detection of intra-plate seismicity. For these reasons, the ANTEC SCAR GoS emphasized the importance of seismic arrays in the continental interior. Preliminary measurements done during previous summer campaigns resulted in the design and the installation of the central observatory. We are now planning to carry out additional tests for the configuration of more challenging remote stations during the next campaign, and to finish the small-aperture array.
All activities at Dome C are in cooperation with Ecole et Observatoire de Physique du Globe of Strasbourg University, France. The microseismic campaigns are in cooperation with Scientists from the Institute of Geological and Nuclear Sciences (Lower Hutt, NZ).