Major earthquakes led to stunning changes in Kashsh district, Gujarat state: study

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A study of sediment samples has revealed that the major earthquake events of the past 30,000 years have led to stunning changes in the landscape of the Cattrol Hill Fault in the Kashish District of Gujarat. These surprising geological facts about the fault’s seismic history in the recent geological past necessitate a review of seismic hazard assessment and mitigation strategies in the Kashch Basin, given its proximity to the industrial corridor and major settlements, including the city of Buj.

Earthquakes are one of the natural hazards that geologists still face with their complex nature. The complexity is attributed to its spread across space and time. Earthquakes in the Kasha region are very complex because they are characterized by multiple seismic sources in the form of many east-west fault lines, which release continually accumulating tectonic pressures at intervals that produce earthquakes. Real-time monitoring of seismicity since the devastating 2001 Bug earthquake indicates that most faults in the region, such as the Kasesh Main Fault (KMF), the Southern Wagd Fault (SWF), the Gedi Fault (GF) and the Island Belt Fault (IBF) are seismically active. However, seismic activity along other faults such as the Cattrol Hill Fault (KHF) is not apparent, making the task of estimating and mitigating seismic hazards in the region a scientifically complex process.

Geoscientists from the Department of Geology, Maharaja Sayajirao University of Baroda, Vadodara, are trying to decipher seismic activity in Katch using geological methods. Recent focused studies of this research group led by Professor LS Shamial and later Professor DM Moriah on the poorly understood Cattrol Hill Fault (KHF) have estimated the length of the surface rupture caused by three large-scale earthquakes during the past ~30,000 years to be approximately 21 km. This study was conducted through field mapping and the use of sophisticated field tools such as ground penetrating radar and laboratory equipment such as scanning electron microscope to analyze sediment samples.

This research published in “Engineering Geology” and “Earth’s Surface Processes and Earth Shape” is made possible by advanced scientific equipment funded mainly under the FIST program of the Department of Science and Technology, Government. India. The equipment located at the Department of Geology, Maharaja Sayajirao University of Baroda, Vadodara, is actively used in advanced research in geological and allied sciences.

The team of geologists at the university conducted a high-magnification scanning electron microscope study of the surface of sediment samples collected along the fault line, which showed features indicative of surface cracking. Based on various inferred fault parameters such as surface rupture length, displacement and slip rate, the study shows that the Cattrol Hill Fault (KHF) has produced large-scale seismic events over the past approximately 30,000 years, and is thus a reliable seismic source. Capable of generating a surface rupture hazard in the Kachah Basin.

Moreover, field geomorphological studies revealed that the events led to stunning changes in the landscape, as evidenced by the disruption and reorganization of the Junawari River channel in the rift zone. It is interesting that these events ruptured the surface, whereas the 2001 Boge earthquake (Mw 7.7) did not rupture the surface. Ancient earthquakes along the Cattrol Hill fault caused a surface rupture, possibly because they originated at relatively shallow depths. However, these events show a much longer recurrence interval for the King Fahd reservoir on the millennia scale compared to other seismically active faults in the Kasha Basin.

(with input from PIB)

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