Microgravity Estimation of Filling up the Near Surface Mineshaft - Example of the Gravity Modelling Usage

The study presents an example of application of the microgravity method in estimation of the degree of filling up old mineshafts, whose existence may be dangerous for the near surface and the infrastructure located on the area. The field data was collected in the area of mining excavations located near the city of Olkusz (Lesser Poland province). The relaxations spreaded in the surrounding of an unfilled object caused emergence of the near-surface deformations, futhermore it causes damages of buildings. An essential part of this study was to discover which objects had been totally filled up and do not create any danger for surrounding infrastructure, and which mineshafts are filled to insufficient extent. One of useful methods of quantitative interpretation of gravity image is gravity modelling. It consist in the calculation of the gravity effect for the customary models and its comparison with measured gravity anomaly, in order to obtain compatibility between field and teoretical curve (with margin of RMS error).