8 July 2019, the XXVII General Assembly of the International Geodetic and Geophysical Union (IUGG) was held in Montreal, Canada. This is a unique scientific event that takes place every four years. The main goal of the conference is to unite a large number of scientists from different countries working in the field of Earth and space sciences to exchange the latest scientific achievements.
Palais des Congrès, Montreal, Canada
The International Union of Geodesy and Geophysics (IUGG) is a non-governmental scientific organization, one of the 40 that make up the International Science Council (ISC). Its interests cover a variety of Earth studies, including solid Earth dynamics, earthquakes and volcanoes, hydrological cycle including snow, ice, and glaciation, science of the atmosphere and ocean, as well as magnetic and gravity fields of the Earth.
It should be noted that this year marks IUGG centennial with the theme “Beyond 100: The next century in Earth and Space Science”. The meeting program included presentation of IUGG work results in 2015-2018. One of the main issues on the agenda was the choice of the venue for the next General Assembly in 2023.
Scientific program of the Assembly included more than 5 thousand presentations on the main areas of geophysical research supported by the eight international associations that make up the IUGG: International Association of Cryosphere Sciences (IACS); International Association of Geodesy (IAG); International Association of Geomagnetism and Aeronomy (IAGA); International Association of Hydrological Sciences (IAHS); International Association of Meteorology and Atmospheric Sciences (IAMAS); International Association for the Physical Sciences of the Ocean (IAPSO); International Association of Seismology and Physics of the Earth's Interior (IASPEI); International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI).
IUGG 2019 had about 200 scientific sections, in which almost 4,000 scientists from 90 countries discussed advanced research in the field of Earth and space sciences. All information about the conference, as well as abstracts, are presented on the website www.iugg2019montreal.com .
FGBU “VSEGEI” was represented by Head of the Department of Regional Geophysics and Geophysical Mapping Dr. T.P. Litvinova and Geophysicist of the Department of Forward Geophysical Bases GGK-200 K.M. Antashchuk.
T.P. Litvinova presented an oral paper in the IAGA section “A22 Significant Achievements in Magnetic Field Studies induced by IUGG over its 100-Year History” – “Significant advances in aeromagnetometric researches in Russia over 100 years”.
K.M. Antashchuk made an oral presentation in the IAGA section “A20 Geophysical Survey Technology for Mining Exploration” - “Study of the Chaun-Chukotka Folded Zone (the Chukotka Fold Area) Based on Joint Interpretation of Geophysical Data”. The presentation was prepared jointly with FGBU “VSEGEI” staff A.I. Atakov, K.N. Mazurkevich. It featured the intermediate results of a comprehensive interpretation of geophysical methods for the Chaun-Chukotka folded zone, including the results of airborne magnetic and gravity surveys on sheet R-59, seismic surveys and MT sounding on regional lines 2-DV and 2-DV-A. The main research results are a diagram of tectonic structure of the area, built on the basis of data from potential fields, including multidirectional tectonic faults. According to the results of studies on regional lines, it was shown that northeast striking discontinuous faults control the sinking of the Palaeozoic basement in the southeast direction. A change in mineragenic zones on the surface is associated with the basement dipping. In general, the presentation was fully consistent with the level and theme of the section.
This section also featured presentations on marine electrical exploration: CSEM, TEM, and IP, in the prospecting and study of sulphide deposits in MOR areas. Since marine modifications of these methods are quite young, work and data inversion technologies are being actively developed, 3D inversion algorithms are being elaborated to consider the complex seafloor bathymetry in MOR areas.
A large number of presentations were devoted to the application of MT studies for prospecting for ore deposits in a wide frequency range that can localize anomalies from the level below crust to local anomalies associated directly with ore target.
It should be noted that in the majority of reports on MT studies, 3D inversion is used in the ModEM software (www.modem-geophysics.com). Of course, when solving regional tasks and mapping deep anomalies, the use of 3D inversion is the most appropriate tool, because avoids a large number of errors associated with 2D approximation. At the same time, it should be noted that with more detailed work and studying to depths of several kilometres, 2D and 1D inversions remain, at the moment, more relevant, because allow to achieve a good resolution and structured geoelectric section.
The section “Advances in EMI Theory” was mainly devoted to the issues of EM data inversion. J. Velimsky (Charles University, Prague, Czech Republic) made presentation “Recovering the Mantle Electrical Conductivity from Swarm: Results after 5 Years”, which examined the results of 1D and 3D data inversion obtained after 5 years of the mission of the Swarm satellite and ground-based observatories.
In the section “Joint inversion of different geophysical data sets”, presentations on joint 3D inversion of altitude, geoid surface, heat flux, surface seismic waves, geochemical data, and MT soundings for studying the global tectonic structure were of particular interest. It is worth noting the most interesting results that were demonstrated in other sections that were able to visit. The section “Electromagnetic Signals Generated by Volcanic Eruptions/Activity, Fluid Pressure, Earthquakes Aseismic Fault Slip” shows the results of EM observations, both in the MT and ultra-long range, showing the presence of variations associated with earthquakes and volcanic eruptions a few days before the event. Changes in resistivity are associated with changes in fluid saturation of rocks. Changes in the signals of ultra-long-range radio stations are associated with changes in the propagation conditions of radio waves during the preparing earthquakes.
The section “Probing the Earth's Lithosphere and its Dynamics Using Geophysical Modelling” contained a large number of presentations. The following main directions can be distinguished according to the methods used in research. One of the leading ground-based research methods is the integration of seismic and MT sounding data with potential fields. Another area is the use of satellite magnetic observations.
A large number of presentations were devoted to the problem of space weather. This direction is one of the fastest growing, which is associated with its significance for humanity. GICs (geomagnetic induced currents) pose a great threat to both the private and economic sectors, because even short-term failure of power lines can lead to catastrophic consequences. GICs predicting is an important task. However, at the moment there is no universally accepted model of the magnetosphere-ionosphere-thermosphere system, the development of which is necessary for a correct forecast. Significant complexity is represented by the small number of events and their irregularity, which does not allow the correct application of generally accepted statistical methods. The main direction in the field of forecasting is the use of data from magnetic observatories and MT observations to calculate electrical components. When applying this approach, it is necessary to consider the complex three-dimensional nature of the EM field source. The possibility of using ground-based and satellite observations is also shown, allowing you to set the points with the highest activity at the moment. Then, electric fields are simulated for these points using ground-based data. It is shown that using this approach, it is possible to make a forecast for a specific power line 15 minutes before the event.
In general, based on the results of the sections visited, the following main directions actively developing at the moment can be formulated:
- joint 3D inversion of geophysical data;
- issues related to space weather;
- marine operations using EM methods with a controlled source and methods for solving inverse problems for the data obtained;
- airborne electromagnetic sounding and methods for solving inverse problems for the obtained data;
At the exhibition held simultaneously with the conference, the following organizations were represented, among others. AGCOS – Canadian manufacturers of MT equipment (including generators and marine observation stations). Phoenix Geophysics – Canadian manufacturers, one of the world leaders in the production of MT equipment (including generators), GEM – Canadian manufacturers of equipment for ground and airborne magnetic exploration and ultra-long-range electromagnetic sounding. AGCOS and Phoenix Geophysics presented the latest developments in MT techniques and CSEM. It can be noted that the AGCOS MT recorders are multichannel (have 8 independent channels), allow you to implement a large number of electrical prospecting methods (MT sounding, electrotomography, transient electromagnetic method) and are not inferior to competitors in technical specifications. Details of the equipment specifications can be found on the company's website www.agcos.ca. Phoenix Geophysics recorders (company website www.phoenix-geophysics.com) also have 8 channels, but their purpose is set by the manufacturer – 3 electric and 5 magnetic, which, in general, is a drawback. At the same time, AGCOS is less well-known in the MT equipment market and, to date, in Russia there is no experience in its use.
The venue of the upcoming IUGG 2023 General Assembly is Berlin (Germany).