Monitoring Land Surface Deformation Associated with Gold Artisanal Mining in the Zaruma City (Ecuador)

Abstract

<jats:p>Underground mining can produce subsidence phenomena, especially if orebodies are surficial or occur in soft rocks. In some countries, illegal mining is a big problem for environmental, social and economic reasons. However, when unauthorized excavation is conducted underground, it is even more dangerous because it can produce unexpected surficial collapses in areas not adequately monitored. For this reason, it is important to find quick and economic techniques able to give information about the spatial and temporal development of uncontrolled underground activities in order to improve the risk management. In this work, the differential interferometric synthetic aperture radar (DInSAR) technique, implemented in the SUBSOFT software, has been used to study terrain deformation related to illegal artisanal mining in Ecuador. The study area is located in Zaruma (southeast of El Oro province), a remarkable site for Ecuadorian cultural heritage where, at the beginning of the 2017, a local school collapsed, due to sinkhole phenomena that occurred around the historical center. The school, named “Inmaculada Fe y Alegria”, was located in an area where mining activity was forbidden. For this study, the surface deformations that occurred in the Zaruma area from 2015 to 2019 were detected by using the Sentinel-1 data derived from the Europe Space Agency of the Copernicus Program. Deformations of the order of five centimeters were revealed both in correspondence of known exploitation tunnels, but also in areas where the presence of tunnels had not been verified. In conclusion, this study allowed to detect land surface movements related to underground mining activity, confirming that the DInSAR technique can be applied for monitoring mining-related subsidence.</jats:p>

A Mineralogical Museum as a Geotourism Attraction: A Case Study

“…The museum receives 700 tourists a year, with higher values in 2015, 2016 and 2017 than in 2018, 2019 and 2020 (Figure 4). The reasons for the visits' evolution are mainly (i) the problems derived from the land in-stabilities [68] and subsidence events in Zaruma city linked to illegal gold mining [49,69,70], which caused a decrease in the tourist influx in the district in 2018 and 2019, and (ii) the global pandemic by COVID-19 in 2020.…”

Multi-temporal relative landslide risk analysis for sustainable development of rapidly growing cities

“…Sentinel-1A and B images (ascending and descending pass) acquired between October 2016 and May 2019 were processed using the Coherent Pixel Technique -Temporal Phase Coherence (CPT-TPC) approach (Mora et al 2003;Iglesias et al 2015). The obtained Line of Sight mean displacement rates were post-processed through the application of the kernel density estimation (KDE) algorithm, allowing to identify unstable areas (UAs) affected by ongoing deformations (Di Martire et al 2016;Guerriero et al 2019;Ammirati et al 2020). Identified unstable areas were used as a guide for aerial imagery interpretation and subsequent field surveys.…”

Surface and Underground Geomechanical Characterization of an Area Affected by Instability Phenomena in Zaruma Mining Zone (Ecuador)

“…From the orographic point of view, the environment presents high slopes where mass movements linked to triggers such as heavy rainfalls, deforestation, seismic activity, civil works (e.g., roads), and mining are frequent. Since 2015, in addition to occasional landslides, there have been several subsidence events linked to the existence of illegal gold mining [16,38,[49][50][51]. One of the most relevant subsidence events was the one that originated the collapse of the La Inmaculada School in the center of Zaruma in 2017 [49,51].…”

“…Since 2015, in addition to occasional landslides, there have been several subsidence events linked to the existence of illegal gold mining [16,38,[49][50][51]. One of the most relevant subsidence events was the one that originated the collapse of the La Inmaculada School in the center of Zaruma in 2017 [49,51]. This event caused an increase in restrictions on mining activity below the urban area of Zaruma (Figure 1b) defined in the decree of the mining exclusion zone (EZ) (Ministerial Agreement No.…”