Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil

Abstract

Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can affect natural and built environments, threatening public safety. The use of multiple geophysical approaches may offer an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their efficiency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited the depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline.

Identification of Karstification Zoning and Aquifer Channels in Karst Basin at Sendang Biru Beach, Malang-Indonesia: A Case Study

“…The process of karstification often results in natural underground cavities. As a result, dissolution occurs, allowing the formation of caves or creating sinkholes [17]. According to Sahrina et al [25], the epikarst zone is concentrated from rainwater infiltration.…”

“…In addition, this identification has been verified with moderate to high chargeability values with a spreading pattern to a depth of 40 m. It has also been confirmed by Schmutz et al [16] that fractured limestone found in potential natural anomalies has a negative value. Thus, the relatively large accumulation of water flow to the location is interpreted as an aquifer catchment area, and it is the cause of the karstification process of dissolving carbonate rocks [17,62].…”

“…doline cover debris [13][14][15][16]. Then, epikarst features with geophysics [17], and microgravity, ERT, and seismic application to detect karst sinkholes [17,18]. Furthermore, a combination of ERT, IP, and SP methods was applied for the investigation of groundwater in the dissolution process of rock due to intrusion [19], zone of mineralization of graphite content [20], and environmental contamination due to landfill leakage [21].…”

A semi-automatic approach for doline mapping in Brazilian covered karst: the way forward to vulnerability assessment

“…Dolines are characteristic of karstic environments that denote the predominance of subsurface solution processes as outcomes of the interaction of slightly acidic water with soluble rocks such as carbonates. Together with the epikarst, dolines serve as a reservoir for water for the underground environment (Williams, 2008) and a direct connection between surface morphology and underground environments (fauna and speleothems) making their detailed investigation an essential step in the cave vulnerability and hazard assessment (Hussain et al, 2020a(Hussain et al, , 2020b. The identification and mapping of dolines can also be used to obtain morphometric data for karstification rate estimation and to determine the evolution of karst landscapes (Williams, 1972;Day, 1976).…”

“…The example can be taken off the Corrente river basin including APANRV, where there is still non-availability of detail databases required for the accurate identification of the dolines. An attempt had been made in the past for such identification using different geophysical techniques by Hussain et al, (2020aHussain et al, ( , 2020b. However, the scale of the study was too small to be considered for the assessment on a large scale.…”