Study of Integrated Geophysical and Geological Research Methods on Mapping Weakness Structures in Bedrock at Urban Areas

Abstract

This abstract present one example site from a short project where the idea was to develop integrated geophysical and geological research methods for the urban studies for detecting fracturing and mapping weakness structures in the bedrock. The sample case is located in the route of planned west metro line in the City of Espoo. The area is called Hannusjarvi. The geophysical methods included old airborne interpretations as well as different ground geophysical test measurements together with geological interpretations from existing data and interpretations. Bedrock drilling data for this project was distributed by the West Metro Project. The old interpretations of weakness zones were produced in two earlier projects using aerogeophysical data and topographic models combined with structural geological analysis. The use of different ground geophysical methods was considered according to methodological and geological features. Magnetic, gravimetric, ground penetrating radar, electrical resistivity tomography and electromagnetic methods were utilized in test with new geological mapping. The combined geological and geophysical interpretation gave promising results and new information about the possible fractures and weakness zones in the vicinity of the new metro line. The ongoing excavation of the metro tunnel gives data to verify the geophysical and structural geological interpretations made in this project.