Delineation of Earthquake-Induced Buried Palaeochannels Through Remote Sensing and Geophysical Surveys

The present study focuses on identifying and interpreting palaeochannels in the eastern part of the Great Rann of Kachchh (GRK), near Khadir Bet Island in the Kutch district of Gujarat, India. This region is historically significant due to the hypothesized course of the ancient Lost River. The aim of the study is to distinguish the subsurface signatures of water eruption (sand injection) due to soil liquefaction after Bhuj Earthquake (2001, 7.7M). Landsat NIR-band imagery was utilized to identify areas affected by water eruption. A comparison of pre-earthquake and post-earthquake satellite data revealed distinct spectral signatures indicative of water eruption, suggesting significant surface changes following the seismic event. To investigate the subsurface characteristics of the affected area, Ground Penetrating Radar (GPR) of 40 MHz and 100 MHz and Electrical Resistivity Tomography (ERT) surveys were conducted along a 400 m profile. The radargrams revealed several subsurface discontinuities characterized by disrupted reflection patterns, which are interpreted as buried palaeochannel networks. The ERT inverse model provided a two-dimensional resistivity distribution along the profile to a depth of approximately 93 m. A prominent low-resistivity zone was identified between 200 and 240 m along the profile, particularly at depths ranging from 20 to 60 m. Resistivity values within this zone range from 0.569 to 3.16 Ω·m, indicating the presence of water-saturated sediments and suggesting the occurrence of an ancient river channel or a fault-controlled depositional feature. In contrast, higher-resistivity zones on either side of the anomaly likely represent compact, relatively dry, or rocky strata that act as geological boundaries. The integrated interpretation of Landsat imagery, GPR, and ERT data demonstrates the effectiveness of geophysical and remote sensing techniques for mapping buried palaeochannel systems in saline environments and subtle geomorphic settings. The study establishes a systematic framework for palaeochannel identification and provides a basis for future investigations.