Measurements of snow water equivalent (SWE) constitute an important input to hydrological models used to predict snowmelt runoffs. The new generation of such models use distributed snow data, including distribution of SWE, as input, and rely on it for calibration and validation. Using ground penetrating radar (GPR) from snowmobiles or helicopters is one of the methods to estimate SWE, and it allows for covering large areas in a short period of time. However, the accuracy offered by GPR is detrimentally affected by the presence of liquid water in the snow. This is a problem since when a snowpack is at its peak, and therefore of the largest interest, it has quite often started to melt so there might be liquid water in the snowpack. The present work is an attempt to solve this problem for SWE estimates made by multi-offset GPR operated from a snowmobile. The main idea is to use radar data already available, and to utilize, in addition to two-way travel time, radar wave attenuation, which both depend on snow wetness. Thus obtained liquid water content of a snowpack can be used to get more accurate estimates of SWE.Using radar wave attenuation to obtain liquid water content requires the relationship between liquid water content and electrical conductivity, which has to be established experimentally. The results of several series of experiments, first establishing this relationship for a specific salt content, and then confirming that variation in salt content does not significantly affect it, are presented in this work.However, there remains another problem to be solved. Attenuation caused by energy dissipation in the snow can only be determined from measured radar wave amplitude if losses due to reflection at the snow/ground interface are known. Since a multi-offset GPR system is in fact an array of antennas, several measurements can be made at each point with radar waves reflecting from the ground with different angles of incidence. It should therefore be possible to calculate angle-dependent reflectivity from radar wave amplitudes using Snell's law and one of Fresnel equations. However, applicability of this method in the presence of measurement errors has to be verified. Initial experiments point to problems due to antenna ring-down from the direct wave interfering with the reflected wave, so further tests of the method should be conducted, or ultimately another method to determine reflectivity of the snow/ground interface should be found. Theoretical and experimental results presented in this thesis lead to the conclusion that when SWE is estimated with a multi-offset GPR system, radar wave amplitudes, available in radar data, can be used to establish liquid water content of a snowpack and hence improve the accuracy of SWE estimates, provided that the problem with establishing reflectivity of the snow/ground interface is solved.

A great number of field measurements with different methods and instruments were conducted in attempts to develop a method for an optimal combination of various geochemical and geophysical methods in archaeological prospecting. The research presented in this thesis focuses on a study of how different anthropogenic changes in the ground can be detected by geochemical and geophysical mapping and how the results can be presented. A six-year pilot project, Svealand in Vendel and Viking periods (SIV), was the beginning of this work in which EM- measurements, gradiometer and GPR surveys together with phosphate mapping succeeded in detecting settlements, mainly from the Iron Age. During the project, a new field kit for soil phosphate analysis was also developed and patented. Another major project was the examination of the Kings’ Mounds in Old Uppsala where a multi method survey including two different slingrams, three different types of GPR equipments and two different gradiometers was used for detecting structures inside the mounds. The Thing Mound was interpreted not to be a burial mound. The layers indicated by the GPR survey are most probably natural glaciofluvial layers. At the Eastern Mound the measurements detected an excavation tunnel from 1846-47, some known old brick furnaces from the time of building of the church, the original esker surface and the central cairn. The survey also detected two linear structures from the mounds base to the top and a depression under the mound in the old esker. The linear structures were interpreted as possible boulder rows and the depression as a possible older burial preceding the construction of the mound. Other surveys with slingram and GPR were used to detect subsurface features at historical gardens and historical glass works. A number of surveys to detect older church remnants were also carried out. In a project at Arethousa, Greek Macedonia, slingram measurements pointed out possible subsurface stonewalls and a possible hearth, which were confirmed later by excavations. At Old Uppsala, Sweden a GPR survey was successfully used for detecting the older cathedral under the present church. The overall results led to a recommended concept of combined methods for archaeological prospecting, especially in northern Europe. Slingram measurements of both electrical and magnetic components combined with phosphate mapping and GPR surveys proved to be useful methods for such prospecting.

<p>Høye poretrykk utgjør en risiko for boreoperasjoner på Norsk Sokkel og internasjonalt. Denne risikoen kan reduseres dersom man har kjennskap til poretrykksforholdene før boring. Poretrykk er også en viktig parameter for felt i produksjon, og kunnskap om hvordan dette utvikler seg over tid vil kunne ha stor betydning for økt oljeutvinning. Seismiske data inneholder informasjon om poretrykket og kan derfor bidra til økt kunnskap på dette området. Avhandlingen tar for seg hvordan hastighets- og amplitudeinformasjon fra seismiske data kan brukes for å estimere poretrykk.</p> / <p>Abnormally high pore pressures in the subsurface pose a hazard to drilling operations worldwide. The problem is not unusual on the Norwegian Continental Shelf. Knowledge of the pore pressure prior to drilling may reduce the risk related to drilling in high pressure zones. Pore pressure is also a vital paramter for producinig fields, and knowledge of how the pressure develops over time can be important for increased oil recovery. Seismic data contain information on the pore pressure and may contribute to increased understanding of subsurface pressure conditions. The thesis deals with methods for estimation of pressure from seismic velocity and amplitude data.</p>

Høye poretrykk utgjør en risiko for boreoperasjoner på Norsk Sokkel og internasjonalt. Denne risikoen kan reduseres dersom man har kjennskap til poretrykksforholdene før boring. Poretrykk er også en viktig parameter for felt i produksjon, og kunnskap om hvordan dette utvikler seg over tid vil kunne ha stor betydning for økt oljeutvinning. Seismiske data inneholder informasjon om poretrykket og kan derfor bidra til økt kunnskap på dette området. Avhandlingen tar for seg hvordan hastighets- og amplitudeinformasjon fra seismiske data kan brukes for å estimere poretrykk. / Abnormally high pore pressures in the subsurface pose a hazard to drilling operations worldwide. The problem is not unusual on the Norwegian Continental Shelf. Knowledge of the pore pressure prior to drilling may reduce the risk related to drilling in high pressure zones. Pore pressure is also a vital paramter for producinig fields, and knowledge of how the pressure develops over time can be important for increased oil recovery. Seismic data contain information on the pore pressure and may contribute to increased understanding of subsurface pressure conditions. The thesis deals with methods for estimation of pressure from seismic velocity and amplitude data.

<p>A great number of field measurements with different methods and instruments were conducted in attempts to develop a method for an optimal combination of various geochemical and geophysical methods in archaeological prospecting. The research presented in this thesis focuses on a study of how different anthropogenic changes in the ground can be detected by geochemical and geophysical mapping and how the results can be presented.</p><p>A six-year pilot project, Svealand in Vendel and Viking periods (SIV), was the beginning of this work in which EM- measurements, gradiometer and GPR surveys together with phosphate mapping succeeded in detecting settlements, mainly from the Iron Age. During the project, a new field kit for soil phosphate analysis was also developed and patented.</p><p>Another major project was the examination of the Kings’ Mounds in Old Uppsala where a multi method survey including two different slingrams, three different types of GPR equipments and two different gradiometers was used for detecting structures inside the mounds. The Thing Mound was interpreted not to be a burial mound. The layers indicated by the GPR survey are most probably natural glaciofluvial layers. At the Eastern Mound the measurements detected an excavation tunnel from 1846-47, some known old brick furnaces from the time of building of the church, the original esker surface and the central cairn. The survey also detected two linear structures from the mounds base to the top and a depression under the mound in the old esker. The linear structures were interpreted as possible boulder rows and the depression as a possible older burial preceding the construction of the mound.</p><p>Other surveys with slingram and GPR were used to detect subsurface features at historical gardens and historical glass works. A number of surveys to detect older church remnants were also carried out. In a project at Arethousa, Greek Macedonia, slingram measurements pointed out possible subsurface stonewalls and a possible hearth, which were confirmed later by excavations. At Old Uppsala, Sweden a GPR survey was successfully used for detecting the older cathedral under the present church.</p><p>The overall results led to a recommended concept of combined methods for archaeological prospecting, especially in northern Europe. Slingram measurements of both electrical and magnetic components combined with phosphate mapping and GPR surveys proved to be useful methods for such prospecting.</p>

During 1979, an oil prospecting project was initiated in the south of Sweden, outside the coast of the municipality of Skåne. No drilling program was initiated, and the project was put on ice. However, with the oil prices of today and the interest in carbon dioxide storage, the area could once again be interesting. In this thesis, 3 seismic lines have been reprocessed with new software, Claritas, in an attempt to obtain information of the area. The thesis is also thought of as an easy to read tutorial as to how oil prospecting works. The result of the reprocessing showed that the new software could reduce multiples and high- and low frequency noise with an fx-decon filter. / Under 1979 inleddes ett projekt med oljeprospektering utanför Skånes kust i södra Sverige. Inget borrprogram initierades och projektet lades ned. Med dagens oljebrist och intresset för koldioxidförvaring så skulle området än en gång kunna vara intressant. I detta examensarbete har därför 3 seismiklinjer omprocesserats med ny programvara, Claritas, i ett försök att förbättra vår bild av detta område. Examensarbetet är även tänkt att fungera som en inledande litteratur om hur oljeprospektering fungerar. Resultatet av omprocesseringen av seismikdatat visade att man med den nya programvaran kunde reducera multipler och hög- och lågfrekvent brus med ett fx-decon filter.

When analysing volcanic seismicity and volcanic events, it is often interesting to focus on tremor, which is a signal of long duration. This is because not much is known about tremor. Unlike earthquakes, sources of tremor are difficult to locate due to them not having any clear onsets in the seismic signal. Different location methods can be used to attempt to locate tremor sources, one of which incorporates correlation of seismic signals between two different recording stations. This method is sensitive to the frequency content in the signal, and will not operate correctly if the signal consists of non-tremor signals, e.g. earthquakes. Earthquakes generally contain higher frequencies than tremor, and if these are present in the signals being correlated, this will affect the location method negatively. Therefore, it is desirable to try to detect these events containing other frequencies, to be able to remove them from the data and improve the location method. Constructing this method is the objective of the study, and is done using the programming language Matlab. The method uses correlation between the amplitude spectra of short adjacent time intervals of the bigger time series, in an attempt to detect when the spectral signature of the time series radically changes. An outlier is deemed to exist when the correlation coefficient from the comparison falls beneath a pragmatically chosen multiple of standard deviation from the mean of coefficient values. The objective of the study has been achieved, by constructing a method using correlation between time intervals to detect sudden fluctuations in the spectral shape of the time series. The method does seem promising, however, the accuracy of the method now needs to be rigorously tested. Time has not allowed for this to be done in this study, and is left for future research. / När man analyserar vulkaniska händelser och seismik är det ofta intressant att fokusera på tremor, vilket är långvariga händelser. Detta är p.g.a. att inte mycket är känt om des-sa. Till skillnad från jordbävningar, så är orsaken till tremor svår att lokalisera eftersom dom inte har en tydlig början i den seismiska signalen. Olika lokaliseringsmetoder kan användas för att försöka lokalisera dessa orsaker, varav en är en metod som använder sig av korrelationen mellan den seismiska signalen för två olika mätstationer. Denna metod är känslig för innehållet av frekvens i signalen som används i jämförelsen, och kommer inte fungera lika bra om signalerna innehåller annat än endast tremor, t.ex. jordbävningar. Jordbävningar innehåller generellt högre frekvenser än tremor, och ifall dessa är närvarande i signalerna som används i jämförelsen kommer detta påverka metoden negativt. Därför är det önskvärt att försöka hitta dessa händelser som ger upphov till andra frekvenser, för att sedan kunna avlägsna dessa och förbättra lokaliseringsmetoden. Målet med detta projekt är därmed att konstruera denna metod, och detta genomförs i programmeringspråket Matlab. Metoden använder sig av korrelation mellan amplitudspektrum av korta närliggande tidsintervall från den större tidsserien, för att försöka detektera när frekvensinnehållet i signalen ändras radikalt. Ett interval anses vara en avvikelse närkorrelationskoefficienten från jämförelsen faller under en pragmatiskt vald multipel av standardavvikelsen av medelvärdet av korrelationskoefficienterna.Målet med projektet har uppfyllts, genom att konstruera en metod som använderkorrelation mellan tidsintervall för att detektera plötsliga fluktuationer av dom frekvensersignalen innehåller. Metoden verkar lovande, men noggrannheten av den behöver nu testas rigoröst. Tyvärr kunde inte detta utföras inom tidsgränserna av detta projekt, och får lämnas som framtida forskning.

A great number of the urban areas in Ethiopia are situated within the Great Rift Valley of Ethiopia, a system consisting of depressions and large faults. As a region with significant seismic activities, it is vital that careful planning is implemented to avoid constructing buildings on flat surfaces as they can amplify ground motion in the case of an earthquake.   This study was conducted in Adama, a city located within the rift system, to map and characterize the subsurface of a construction site with seismic refraction and investigate whether this is an optimal area to construct a building should an earthquake occur. Seismic refraction is based on Snell’s law, specifically the case of the critical angle, which is when the refracted angle is at 90 degrees and a number of the energy from the wave is rebounded back to the surface in accordance with Huygen’s Principle.       Seismic waves were generated with a sledgehammer and recorded with 24 vertical geophones. The acquired data was then analysed with SeisImager and produced a 2D-tomography of the site with the corresponding velocity layers for a P-wave. Comparing the P-wave velocities to a table of Seismic Velocities of Rocks and Various Materials, one could determine that the subsurface layers consisted of rock soils, sand and silt. These are incredibly loose materials that will amplify ground motion during earthquake crisis and are therefore not optimal or ideal for constructing buildings.

A high resolution magnetic survey was carried out at the archaeological site of Birka, situated approximately 20 km west of Stockholm. A new-generation optically pumped cesium magnetometer, G-858 from Geometrics, with a maximum sensitivity of 0.01 nT was used in the survey. An area of totally 504 m2 was covered in three windy days in September 1997 with the cesium magnetometer working in vertical-gradient mode. Remnants of the old houses, some of the oldest ditches and an earlier excavation could be seen in the gradient data after processing. Also a total-field measurement was carried out to search for the oldest defence wall at Birka. The bad positioning that followed with the continuous-scan mode made the data very difficult to process efficiently. Some processing was done in Matlab to eliminate effects that might be caused by the geology, but no substantial archaeological results emerged.This work shows that high resolution magnetic surveys can be efficient in detecting archaeological remains even in a very heterogeneous soil, provided very sensitive equipment and correct choice of method. It also emphasized the importance of good positioning in a survey.

The Rajapalot gold-cobalt project in northern Finland is an exciting, relatively new discovery, still being explored with hopes to start mining in the future. The area was found by a IP/Resistivity survey in 2013. Extensive geophysical follow-up surveys have delineated several electromagnetic targets, one of which, named Raja, is the target anomaly this master thesis is built upon. A TEM survey was carried out during late August to early September 2018. The data collected was analyzed, processed and later modelled in Maxwell using Leroi, a CSIRO module. Three separate models are produced with one, two, and three plates respectively. The result is compared to existing VTEM and resistivity models. / Rajapalot guld-kobolt-projektet i norra Finland är en spännande, relativt ny upptäckt som fortfarande undersöks med hopp om att starta gruvbrytning i framtiden. Området upptäcktes via en IP/Resistivitets-undersökning under 2013. Omfattande geofysiska undersökningar har avgränsat flera elektromagnetiska anomalier, varav en, döpt Raja, är den anomali som den här masteruppsatsen är uppbyggd kring. En TEM-undersökning utfördes under slutet av augusti, början av september 2018. Insamlade data analyserades, bearbetades och modellerades senare i Maxwell med hjälp av Leroi, en insticksmodul från CSIRO. Tre separata modeller togs fram med respektive, en, två, och tre plattor. Resultatet jämfördes mot befintliga VTEM-, och resistivitetsmodeller.