The recent study by the scientists of the Indian Institute of Geomagnetism (IIG) has added a new dimension to our understanding of earthquakes. The research, part of the interdisciplinary program ‘Coupled Lithosphere-Atmosphere-Ionosphere-Magnetosphere System (CLAIMS)’, examines seismic signatures in the ionosphere with an aim to derive the seismic source characteristics.
The Role of IIG and It’s Interdisciplinary Program
As an autonomous entity within the Department of Science and Technology, IIG dedicates itself to the study of geomagnetism and related fields. Their program ‘CLAIMS’ mainly focuses on the transfer of energy to the atmosphere during Earth processes like earthquakes and tsunamis. This recent research fits seamlessly into the program’s overall agenda.
Understanding Co-seismic Ionospheric Perturbations
The study observed that the spatial distribution of co-seismic ionospheric perturbations (CIP), affiliated with earthquakes, mirrors the ground deformation pattern that develops around the epicenter. The CIP distributions are derived via the Total Electron Content (TEC) data provided by the Global Positioning System (GPS). Essentially, TEC measures the total number of electrons present between a radio transmitter and receiver. Furthermore, the CIP distribution was calculated at ionospheric piercing point (IPP) altitude.
When an earthquake occurs uplifting the Earth’s crust, pressure waves are generated in the atmosphere above. These waves amplify with increasing atmospheric heights and ultimately disturb the ionospheric electron density creating what is known as Co-seismic Ionospheric Perturbations (CIP).
The Complex Nature of CIP
Nevertheless, the evolution of seismic or tectonically-induced ionospheric perturbation is largely influenced by non-tectonic forcing mechanisms. Among the most significant non-tectonic influences include the orientation between the ambient geomagnetic field and seismic-induced neutral wave perturbations, orientation between the moving satellite line of sights and the wave perturbations, and the ambient ionospheric electron density gradient.
Challenges in CIP Identification
One of the main challenges encountered is that the ionosphere is highly dynamic. Perturbations in ionospheric electron density can have various origins, either from above (solar, geomagnetic) or below (lower atmospheric, seismic). This makes identifying CIP a complex task.
Inference and Implications of the Study
The study’s findings emphasize the importance of considering prevailing non-tectonic forcing mechanisms when studying the manifestation of CIP. Consequently, it is anticipated that this research will be instrumental in developing tools for ionospheric-based seismic source characterization.
The Role of Ionosphere
To contextualize the study, it is important to understand what the ionosphere is and its role. Lying 75 to 1000 km above Earth, the ionosphere is the layer of the Earth’s atmosphere that gets ionized by solar and cosmic radiation. It overlaps with the mesosphere, thermosphere, and exosphere, playing a crucial part in atmospheric science.