A brief tilt and strain survey was conducted in the Krafla-Namafjall area in the North of Iceland during August of 1979 in order to study the feasibility of applying solid earth tidal observations in the exploration of volcanic geothermal systems. The rationale of the survey was based on the expectation that various types of geological structures such as rift zones and magma chambers can lead to observable distortions of the local solid earth tidal amplitude field. The field procedure consisted in measuring the local tidal amplitudes and comparing them with normal theoretical amplitudes at the same location. The Krafla volcanic complex is a central volcano traversed by a N-S trending fissure swarm, that has been tectonically and volcanically active since December 1975. Accompanying this activity have been periodic inflations of the Krafla caldera, presumably caused by a flow of magma into a local magma chamber and resulting in long term tilts of the order 0.5 ��rad/day that have been observed at two sites south and southeast of the caldera. In computing theoretical amplitudes the effects of the ocean tides need to be estimated. In the case of north Iceland they are found to be of the same magnitude as the solid earth tides. The amplitudes of the M��� ocean loading tilt at Krafla are estimated to be 0.066 ��rad and 0.032 ��rad for the NS and EW components respectively. The most noteworthy result was obtained at a site in the Namafjall geothermal area inside the active Krafla fissure swarm. The ratios of the observed to the theoretical M��� tidal tilt amplitudes at this site as estimated by a least squares spectral analysis method are found to be 0.9 �� 0.3 and 3.2 �� 1.5 for the NS and EW components respectively. On the basis of some simple order-of-magnitude estimates we can exclude one of the numerous nearby fractures as a possible cause for the EW tilt anomaly and conclude that it is most likely to be generated by a large body of magma below the Krafla fissure swarm. Due to thermoelastic noise other tilt data obtained during this survey turned out to be less reliable. However, our work at a site east of the fissure swarm and southeast of the caldera indicated a possible anomaly. The strain data are highly contaminated by thermal noise and could not be successfully analyzed. These results tend to confirm that tidal tilt observations can be of use in explorations of volcanic and geothermal systems. Our work indicates that a few improvements of the simple field techniques adapted may enhance the quality of data. These include (1) increasing the instrument resolution, (2) selecting sites with surface layers that are incapable of transmitting thermal stresses and (3) obtaining more extensive higher quality temperature recordings, that should enable the thermal noise to be largely removed. / Graduation date: 1981

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Graduation date: 1979

Thesis (M.Sc.) -- University of Adelaide, Dept. of Applied Mathematics, 1981. / Typescript (photocopy).

Thesis (S. M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2009. / Cataloged from student submitted PDF version of thesis. Includes bibliographical references (p. 41-43).

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 30-31).

Proefschrift--Technische Hogeschool, Delft. / Cover title; added t.p., in Dutch. Includes bibliography.

Thesis (Ph. D.)--University of Washington. / Bibliography: l. [111]-113.

Current and temperature data were acquired in the source region of the Somali Current, jointly by the Universities of Kiel and Miami, as part of the INDEX pilot studies. The data were acquired over a six-month period (January-July, 1976) which spans the springtime Monsoon reversal. The experiment and the data are described in Düing and Schott (1978). This thesis describes the results of the spectrum analysis of fluctuations found in data from the experiment's two southernmost sensor locations. It is found that, once the annual cycle is removed, most of the variance in these current and temperature records resides in subinertial fluctuations. The most prominent spectral feature is a 40- to 50-day peak. This 40- to 50-day period is coincident with that of the global-scale circulation cells found in the tropical atmosphere by Madden and Julian (1971 and 1972). The analysis of wind stress and wind stress curl data for the years 1976 and 1979 presented in this thesis indicate that the 40-to 50-day oscillation was present over the Western Indian Ocean during these years. It is suggested here that wind-forcing excites a long coastally trapped wave. To test this idea, a wind-forced quasi-geostrophic, three-layer model and a reduced-gravity model incorporating lateral mean current shear are applied to the Somali Current regime. Model results suggest that the wind forcing is strong enough to excite the observed current and temperature fluctuations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.