The overall goal of SEMEP was the development of methodologies that could provide information leading to possible short-term forecasting of the occurrence of earthquakes. A joint satellite and ground-based analysis covering two different seismic zones increases the chance of finding electromagnetic perturbations related to different geophysical conditions. In order to reach this goal the following four major scientific objectives were identified:
- The diagnostics of electromagnetic ionospheric perturbations above seismo-active regions and their correlation with ground VLF/LF observations were used to advance our understanding of the coupling between the solid earth and the ionosphere prior to the occurrence of earthquakes.
- The development of physical models that explain the associated seismo-electromagnetic turbulence identified in satellite data.
- The identification of reliable signatures for the precursor phases of earthquakes based on temporal and spatial variations of the signal parameters obtained from multi-station VLF/LF measurements in Europe and the Far East. This improves our knowledge of the physics of earthquake precursors and has enabled the development of practical methods for the short-term forecast of strong earthquakes.
- The investigation of the convective mechanism for the generation of gravity waves in the Earth's atmosphere. Theoretical investigation of the coupling of large scale atmospheric structures with ionospheric perturbations.
The realisation these objectives resulted in the following activities:
- Development of short-term methods for determining the time, location and magnitude of impending earthquakes using multi-station ground observations and satellite observations.
- Analysis of simultaneous satellite and ground VLF signals of ionospheric perturbations, both connected with earthquakes and related to ionosphere/magnetosphere natural processes (magnetic storms, solar flares etc.), in the Asian and European regions.
- Consideration of non-linear wave-wave interactions from correlations of VLF signal spectrum broadening, ionospheric turbulence and electron density perturbations in the upper ionosphere in association with seismic disturbances, volcanic eruptions and magnetic storms;
- Investigations of plasma waves and plasma parameters;
- Estimation of the spatio-temporal scales of earthquake related precursory phenomena and study of the dependence of seismo-electromagnetic phenomena on geological and geophysical properties of the crust.
- Development of theoretical models of energy penetration from the earthquake epicentre, through the atmosphere and ionosphere to the satellite altitudes.
The project was broken down into six scientific work packages corresponding to the type of data used and methods applied to their analysis. The work packages WP1-WP4 were related to satellite data analysis, WP5 concerned base-ground observations, and WP6 covered theoretical investigations of the coupling between Earth's lithosphere, atmosphere and ionosphere.
- Workpackage 1 - VLF/LF signal from ground transmitters received on the DEMETER satellite
- Workpackage 2 - Theoretical and experimental studies of plasma waves in the vicinity of earthquake epicentres
- Workpackage 3 - VLF transmitter signal broadening
- Workpackage 4 - Space plasma parameters from COSMOS-900 and DEMETER data
- Workpackage 5 - Ground-based observations in VLF/LF networks
- Workpackage 6 - Theoretical investigation of the coupling between Earth lithosphere, atmosphere and ionosphere
WP1 involved the development of data processing methods for VLF/LF signals received on board a low Earth orbiting satellite to search for long-period seismic effects and also the correlation of satellite observations of electromagnetic anomalies above seismo-active regions with ground-based VLF/LF observations.
WP2 investigated electric and magnetic fields and their fluctuations associated with earthquakes using multi-satellite data analysis. Experimental results were used in the development of physical models to explain the associated seismo-electromagnetic turbulence.
WP3 was initially aimed at investigating and characterising effects responsible for the broadening of VLF transmitter signals. However, preliminary investigations showed that the relative amplitudes of signals from dual frequency transmitters were very sensitive to perturbations in the ionospheric plasma environment. As a result, the focus of this workpackage was redirected to investigate this phenomena in more detail.
WP4 investigated fluctuations in the ionospheric plasma parameters in relation to seismic activity.
The aim of WP5 was to provide support for satellite observations for the identification of wave-plasma anomalies recorded above seismically active regions. This also included the improvement of current techniques for the analysis of ground-based, multi-station VLF observations for reliable the selection of local perturbations in the ionosphere connected with seismic events and to distinguish between those resulting from global disturbances. The second aim of the WP was the correlation of the spatial-temporal scales of earthquakes related to precursory phenomena with geological and geophysical properties of the Earth crust.
WP 6 investigated theoretical models for the transfer of energy from the region of the earthquake epicentre into the upper atmosphere and ionosphere.
This strategy ensured that each of the individual workpackages delivered major advances while the collective effort across WPs remained focused on integration to achieve the main objectives of the project.
The participants of the SEMEP project have accumulated substantial experience in study of earthquake related phenomena using ground-based and satellite observations. New methods investigating the global diagnostics of seismicity using both DEMETER and ground based VLF signals were developed and tested using seismic observations from Japan. These comparative studies (involving the integration of different advanced theoretical and experimental studies) included the clarification of the physical mechanisms responsible for generating the seismo-electromagnetic phenomena and the development of theories for energy penetration from earthquake epicentre, through the atmosphere and ionosphere and up to satellite altitudes.
The implementation of the SEMEP project has filled several significant gaps in our understanding of the physics of the formation of ionospheric disturbances caused by seismic activity. The results have enabled further development of the methods used for short-term forecasting and early detection of large-scale natural disasters such as earthquakes and volcanic eruptions.