Remote Sensing and Statistical Analysis of Fracture Populations Around Lake Thingvallavatn, SW Iceland

• Main Author: Oxenstierna, Johan
• Format: Others
• Language: English
• Published: Uppsala universitet, Institutionen för geovetenskaper 2012
• Subjects: Geology; Geologi
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182201

This study aims at a description and statistical analysis of tectonic and magmatic fractures in the Western Volcanic Zone (WVZ) on Iceland. Two fracture populations are studied with respect to their distance to the Hengill volcano: The southern area is between 0-10 kilometers from the volcano and the northern area is between 16-25 kilometers from the volcano. The description and analysis of fractures is carried out separately for the two areas as well as for the two areas together to test different mapping procedures, statistical methods and the influence of the volcano on the properties of the fractures. There are various reasons for considering this an important study: Firstly, this is not an extensively researched field and there are many unanswered methodological questions on how to map and describe the fractures. In this study, problems such as how maps are stitched and georeferenced, how fractures are divided into segments and mapped in respect to topography, are discussed. The potential errors caused by these methodological problems are concluded to be large enough to significantly affect statistical tests analyzing fracture populations. In the analysis part, the properties of the fracture populations are studied using Kolmogorov Smirnov and χ 2 goodness-of-fit tests, scatter-plots, simple count and ratios among other methods. It was found that the fracture populations follow distributions that are not easily defined, but that they are of the same and quantifiable type. With more data their common distribution could therefore be modeled, and the factor by which the Hengill volcano affects the strike of fractures per distance unit from the volcano could be calculated. It was also found that magmatic fractures are formed in a similar, but not necessarily the same stress-field as tectonic fractures. Therefore change in magma pressure might change the local stress regime around magmatic fractures, affecting their strike.