As Gujarat prepares to observe the 25th anniversary of the devastating 2001 earthquake next month, a groundbreaking scientific study has provided crucial insights into why certain regions, particularly Kutch, experience frequent tremors. The answer lies deep beneath the Earth's surface, in a complex network of interacting fault lines and crustal deformations.
The Science Behind Gujarat's Shaking Ground
Researchers from the Institute of Seismological Research (ISR) in Gandhinagar, in collaboration with Maharaj Agrasen University in Himachal Pradesh, conducted an extensive analysis to 'scan' Gujarat's underground structure. Their study, published in the prestigious Elsevier journal Tectonophysics, examined over 1,300 tremors recorded between 2008 and 2024. This data was gathered from a network of 56 permanent and 20 temporary seismic stations spread across the state.
The research paper, titled 'Complex nature of the crustal anisotropy in the western margin of the Indian subcontinent and its geodynamic implications,' was authored by Sowrav Saikia, Rakesh Prajapat, Sumer Chopra, Santosh Kumar, Vinay Kumar Dwivedi from ISR, and Vikas Kumar from both ISR and Maharaj Agrasen University.
Kutch Rift Basin: A Hotspot of Deformation
Lead researcher Sowrav Saikia told TOI that the most striking finding was the exceptional nature of the Kutch region. Geologically known as the Kutch rift basin, this area exhibits significantly higher levels of crustal deformation compared to the rest of Gujarat. Crucially, this deformation aligns strongly with major active fault systems.
The primary faults identified include the Kutch Mainland Fault, South Wagad Fault, Allah Bund Fault, and Gedi Fault. These are the very fault systems responsible for historical large earthquakes in the region. The study notes that Kutch has recorded at least four earthquakes of magnitude 6 or above, including the massive magnitude 7.8 quake in 1819 at Allah Bund and the magnitude 7.7 earthquake in 2001 that devastated the region.
Varying Deformation Patterns Across Gujarat
The researchers focused on studying anisotropy, which refers to the directional dependence of deformation within the Earth's crust. They aimed to determine if this deformation aligned with large, known fault lines or was influenced by smaller local structures.
The findings revealed a geographical split. In Saurashtra and the Narmada rift basin of South Gujarat, the crustal deformations closely follow the patterns of local fault structures. However, the scenario is different in North Gujarat and the Cambay rift basin. Here, the direction of deformation aligns more with the broader, relentless northward movement of the Indian tectonic plate as it pushes against the Eurasian plate.
This interaction creates immense and persistent stress accumulation within the crust, especially in confined areas like Kutch where multiple faults interact.
Long-Term Implications for Seismic Hazard Assessment
The study carries significant implications for understanding Gujarat's seismic future. In the short term, it explains the frequent earthquake activity in specific zones. In the long term, it indicates that regions like Kutch are likely to remain seismically active for the foreseeable future due to the complex and ongoing tectonic processes.
When asked about implications for building codes and vulnerability assessments, the researchers clarified that prescribing specific changes was not the study's primary focus. However, they emphasized that their work provides a vital scientific framework for examining deformation and stress within the crust.
By pinpointing zones of active deformation and their controlling fault systems, the study offers invaluable data for earthquake hazard assessment. This scientific information can be integrated with engineering standards, urban planning initiatives, and risk mitigation studies to enhance Gujarat's preparedness for future seismic events.
The research underscores the importance of continuous seismic monitoring and incorporating advanced geological understanding into the state's disaster resilience strategy, especially as it remembers one of its most tragic natural disasters a quarter-century later.
