Volcanic earthquakes can provide significant insight into physical processes acting at volcanoes, such as magma accumulation and the mechanisms of deformation of the volcanic edifice. At the same time a statistical analyses of volcanic seismicity prior to an eruption (for example variations in the Gutenberg-Richter b-value – a measure of the proportion of large and small events) are a key component of the practical problem of forecasting eruptions. This thesis aims to tackle two key areas of research that are closely related to these important overall goals, by comparing seismic data obtained from currently-active volcanoes with direct field observation of faulting and fracturing from an exhumed extinct volcano. First I introduce a new approach that improves the accuracy and reliability of calculating spatial and temporal variations of the seismic b-value for frequency-magnitude distributions at active volcanoes, and apply it to several test cases. An extensive literature review highlights a large variability and lack of standardisation of methodology used to analyse frequency-magnitude distributions in the past. Motivated by this, I introduce and test a new workflow to standardise calculating completeness magnitudes of seismic catalogues. The review also highlights the fact that uncertainties in estimating the threshold magnitude of complete reporting have been ignored to date. Here I use synthetic catalogues to quantify this previously unidentified source of error, and provide a template to estimate the total error in b-value. In standard analysis it is also common to sample time windows subjectively, although this can introduce bias. Here I develop a new objective, iterative sampling method that calculates the b-value as a full probability density function which need not have a Gaussian error structure. Application of this method reveals ‘mode-switching’ behaviour for the first time in volcanic seismic catalogues. The results also show b-values often do have a value indistinguishable from that of tectonic seismicity (b=1 within error). Nevertheless there are also several robust examples of real high b-values, as high as 3.3. The second part of the study is based on a field campaign to investigate the fracture zones from an exhumed volcanic setting on the Isle of Rum, NW Scotland. Lithological and structural mapping is used to collect structural data that is then used to quantify and explain complex fracture patterns and the underlying intra-magma chamber processes that occurred there in the geological past. In particular I identify a singular collapse event within the youngest volcanic unit, the Central Intrusion. This is responsible for forming the observed igneous breccias and the lineaments on satellite images that I interpret as contemporaneous faults. Using appropriate scaling relations, I infer the b-value for the Rum lineaments data. This would have been relatively high, at a value of approximately 1.9. The final part of the study compares the fracture data on Rum to earthquake distributions at El Hierro volcano, Canary Islands. Here I show the level of fractal clustering is similar in both an extinct (60 Ma) and a currently active volcano. Both show similar high levels of clustering. However, in both cases there is a difference between the capacity and correlation dimensions (D₀≠D₂), implying the set of rupture sources or mapped fault traces form a multi-fractal set. Broadly, the scaling of fracture sets in an ancient volcano has similar properties to those observed in a modern volcano, except that the Rum data imply a greater absolute degree of spatial clustering of deformation than that for the recent unrest at El Hierro.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1968. / Bibliography: leaves [119]-122. / ix, 122 l illus., tables

Thesis (Ph. D.)--University of Washington. / Bibliography: l. [139]-143.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Includes bibliographical references (leaves 107-114). Also available on microfiche.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 141-147).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Orientador: Antonio José Ranally Nardy / Banca: Marcos Aurélio F. de Oliveira / Banca: Valdecir de Assis Janasi / Banca: Cristina Maria Pinheiros de Campos / Banca: José Eduardo de Oliveira Madeira / Resumo: Os traquitos e dacitos do tipo Chapecó (ATC) e dacitos e riolitos do tipo Palmas (ATP), de idade cretácica, compõem 2.5% dos ~ 800.000 km3 de lavas da Província Magmática do Paraná (PMP) geradas anteriormente à quebra de Gondwana... / Abstract: The Cretaceous Chapecó trachydacites-dacites (ATC) and Palmas dacites-rhyolites (ATP) make up 2.5% of the ~ 800.000 km3 of lava of the Paraná Magmatic Province (PMP), prior to Gondwana breakup... / Doutor

Ground deformation due to volcanic magma intrusion is recognised as an important precursor of eruptive activity at a volcano. The Global Positioning System (GPS) is ideally suited for this application by being able to measure three-dimensional coordinate changes of the monitoring points over time. Due to the highly disturbed ionosphere in equatorial regions, particularly during times of maximum solar activity, a deformation monitoring network consisting entirely of single-frequency GPS receivers cannot deliver baseline solutions at the desired accuracy level. In this thesis, a mixed-mode GPS network approach is proposed in order to optimise the existing continuous single-frequency deformation monitoring system on the Papandayan volcano in West Java, Indonesia. A sparse network of dual-frequency GPS receivers surrounding the deformation zone is used to generate empirical 'correction terms' in order to model the regional ionosphere. These corrections are then applied to the single-frequency data of the inner network to improve the accuracy of the results by modelling the residual atmospheric biases that would otherwise be neglected. This thesis reviews the characteristics of existing continuously operating GPS deformation monitoring networks. The UNSW-designed mixed-mode GPS-based volcano deformation monitoring system and the adopted data processing strategy are described, and details of the system's deployment in an inhospitable volcanic environment are given. A method to optimise the number of observations for deformation monitoring networks where the deforming body itself blocks out part of the sky, and thereby significantly reduces the number of GPS satellites being tracked, is presented. The ionosphere and its effects on GPS signals, with special consideration for the situation in equatorial regions, are characterised. The nature of the empirically-derived 'correction terms' is investigated by using several data sets collected over different baseline lengths, at various geographical locations, and under different ionospheric conditions. Data from a range of GPS networks of various sizes, located at different geomagnetic latitudes, including data collected on Gunung Papandayan, were processed to test the feasibility of the proposed mixed-mode deformation monitoring network approach. It was found that GPS baseline results can be improved by up to 50% in the midlatitude region when the 'correction terms' are applied, although the performance of the system degrades in close proximity to the geomagnetic equator during a solar maximum.

Understanding the nature of mud volcanism, mechanisms of formation, types of eruptions and their relationship to the hydrocarbon systems provides important information about subsurface conditions and geological processes within the South Caspian Basin. A 2D seismic grid in southeastern offshore Azerbaijan is used to define the areal distribution of mud volcanoes and to make a classification of the mud volcanoes based on characteristic seismic features. As a result detailed database for each determined mud volcano is constructed. Analysis of different parameters from this database shows that there is a high concentration of mud volcanoes at the southern part of the study area. It is coincides with the distribution of the subsurface structures within the basin. Mud volcanoes with low relief (several tens of meters) are mainly concentrated in the northeast. Conversely, mud volcanoes with large vertical relief (greater than 200 m) are clustered in the southwest part of the basin. Mud volcano development in the South Caspian Basin is generally linked to faults, which in some instances are detached at the basement level. By using interpreted seismic surfaces it is possible to determine relative time of mud flows from the mud volcanoes. Timing of mud flows reveals to the actual activity of the mud volcanoes and it gives valuable information about possible mechanism of mud volcanism within the South Caspian Basin. Previous studies of the onshore mud volcanoes in Azerbaijan and the results from current work conclude that mud volcano formation within the South Caspian Basin is mainly controlled by tectonic forces and overpressured sediments. Mud volcano activity is not always related to the Maykop organic reach shale succession. It can occur at shallow depths by pressure breakthrough from any stratigraphic zone.