3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Seismotectonic and seismic hazard studies for Madagascar(2022) Rakotondraibe, TsiriandrimananaMadagascar is an island that was once situated in the centre of the Gondwana supercontinent but is now located 1000 km from the East African Rift and about 2000 km from the mid-ocean ridge of the Indian Ocean. Its separation from the African continent (ca. 165-130 Ma) and the Indian sub-continent (ca. 90 Ma) and mantle upwelling that gave rise to the recent volcanism (ca. 28-0.5 Ma) has had significant impact on the geological structure and neotectonics of the island. This thesis focuses on the seismotectonic evolution of Madagascar and assesses the seismic hazard. Data for this project was derived from the 28-station MAdagascar – COmoros-MOzambique (MACOMO) array, as well as stations from the concurrent SEismological signatures in the Lithosphere/Asthenosphere system of SOuthern MAdagascar (SELASOMA) and Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel (RHUM-RUM) projects, and permanent stations of the national seismological network. The combined 56 stations provided a better distribution and density than any previous study. The thesis is presented in three main parts. The first part focuses on seismicity and focal mechanisms. The 695 events recorded and located during the 23-month period of MACOMO observations in 2011-2013 have magnitudes that vary from M1 to M5.3. Twenty-three focal mechanism solutions were determined using Pwave first motion polarities and some clear S-wave polarities. In agreement with previous studies, it was found that central Madagascar is the most seismicallyactive region. Most earthquakes are located near known faults. Normal faulting dominates the central area, while strike-slip and reverse fault mechanisms are predominantly observed near the Antsaba and Sandrakota shear zones in the north, and the Bekily and Ampanihy shear zones in the south. The focal mechanism studies revealed extensional faulting in central Madagascar, which can be explained by the reactivation of older faults by a thermal bulge underlying the region. The faulting style was not well defined in the northern and southern parts as few solutions were determined due to the lower density of stations. In the second part of this thesis, 182 focal mechanism solutions were used to study the characteristics of the stress field. Calculations were performed using a linear inversion technique based on the Michael (1984) method and using a recently calculated velocity model of Madagascar. Results give shape ratios (i.e., relative magnitude of stress axes) that vary from 0.7 to 0.9; a maximum principal stress axis (σ1) that is near-vertical and a minimum principal stress axis (σ3) that is nearhorizontal with a NW-SE orientation. This corresponds to a normal faulting regime. The regional variation of stress and the characteristics of the shape ratio and friction values were determined. The average direction of the stress field is approximately NW-SE in central Madagascar, and trends W-E in the southern and northern parts of the island. In central Madagascar the shape ratio and friction vary from 0.83 to 0.97 and 0.45 to 0.65, respectively; while in the northern and southern parts of Madagascar they vary from 0.3 to 0.5 and 0.5 to 0.7, respectively. The third part of the thesis reports on the assessment of the seismic hazard in Madagascar using data from a catalogue that combines data from the NDC (National Data Center), bulletins produced by the current study for the period between 1975 and 2016, as well as historical earthquake data. The analysis reveals that Madagascar has moderate seismic activity with local magnitude ML ≤ 6. The relationship between the moment magnitude MW and local magnitude ML values was estimated in order to unify magnitude characteristics and create the homogeneous catalogue that is required for seismic hazard studies. A Probabilistic Seismic Hazard Assessment approach (PSHA) was performed using the Kijko and Sellevoll (KS) and Cornell-McGuire methods with two different ground motion models. In order to implement the alternative parameter values in seismic hazard calculation and to attribute uncertainties associated to the input parameter, a logic tree formalism was applied. The Peak Ground Acceleration (PGA) values near major towns in the central region for 10% and 2% probability of occurrence in 50 years are 0.04 g and 0.11 g, respectively. The spectral acceleration for 1.0 s and 3.0 s vary from 0.001 g to 0.01 g and 0.001 g to 0.005 g for 10% probability of vii occurrence in 50 years, respectively; and from 0.02 g to 0.10 g and 0.002 g to 0.01 g for 2% probability of occurrence in 50 years. This work demonstrates that the deployment of additional temporary seismic stations significantly improved our understanding of the seismotectonics of Madagascar, particularly in the northern and southern regions. In summary, we obtained a new magnitude relation, more accurate epicenter locations, better focal mechanism descriptions, and improved the assessment of seismic hazard.Item Entrepreneurial intention in Madagascar's rural areas: The predictive role of the theory of planned behaviour(2018) Ratsimanetrimanana, FenosoaIn Madagascar, a country ranked among the poorest in the world, the major type of entrepreneurship encountered, particularly in rural areas, is a form of self-employment, where individuals, by obligation, decide to create their own job, not for the sake of pursuing opportunity-based entrepreneurship, but to secure livelihood. Subsequently, as the need to be self-employed presupposes intention, this thesis examined the Theory of Planned Behaviour (TPB) as a predictive model in the formation of entrepreneurial intention (El) among the self-employed, in a rural under-researched context. More specifically, through a deductive approach, this study aimed to verify the predictive role of TPB, in its entirety. This was done through the formation process of El and measuring the influence of cognitive variables and psychological factors (counterfactual thinking, dispositional optimism, entrepreneurial alertness) and the contextual factor (access to finance) on the relationship between TPB dimensions and El in Madagascar's rural areas, where gender and level of education could play a role. The purpose underpinning the research was actualized through adopting a cross-sectional survey. The population object of the research was a sample of 1 500 self-employed individuals living in Madagascar's rural areas, obtained through cluster sampling with a quota. The research instrument used was an interview questionnaire consisting of five separate sections, with items inspired by those that have been successfully tested in the frameworks of similar previous work. The research was nonexperimental and adopted either a regression mechanism or a bootstrap method to establish the causal relationship between the variables under study. The results of the study reveal that the predictive role of TPB, in its entirety, with regard to El, was observed only among the male group of respondents. The level of education did not influence the TPB, in its entirety, in predicting El. The relationship between the attitude towards behavior dimension and El was slightly moderated by dispositional optimism and entrepreneurial alertness. Among the overall respondents, cognitive counterfactual thinking, dispositional optimism, and entrepreneurial alertness moderated faintly the relationship between the subjective normal dimension and El. Page The relationship between the perceived behavioral control dimension and El was a little moderated by cognitive counterfactual thinking, dispositional optimism, and entrepreneurial alertness within the overall group of respondents. Access to finance weakly moderated the relationship between cognitive variables and El. Through the thesis, an opportunity to contribute to the advancement of the TPB model emerged when the moderate effects of cognitive variables and psychological factors, as well as the contextual factor, are accounted for with regard to the relationship between TPB dimensions and El. This approach allowed for the expansion of the theory by integrating more contextualized concerns. At a practical level, the thesis suggested that cognitive variables and psychological factors as well as the contextual factor, as antecedents to El, need to be nurtured to stimulate increased entrepreneurial initiatives within an environmental context relevant to women, comprising of the design, development and delivery of entrepreneurial training, mentoring, and incubation programs. For future investigations, it would be interesting to scrutinize how cultural dimensions might influence the relationship between TPB dimensions and El.Item Molecular Genetic Variation in the Malagasy(2001) Dorf, CindyABSTRACT The island of Madagascar has been separated from Africa for almost 70 million years and was the last of the major land masses to be colonised by humans. Several theories concerning Malagasy origins have been proposed, but the prehistory of the Malagasy is still unresolved. Historical, archaeological, linguistic and genetic data suggest two major contributors to the Malagasy, namely African and Indonesian populations, with additional contributions from Arab, Indian, Chinese and various other Asian sources. All the islanders speak a common language called Malagasy, and although there are dialectical differences, these are not sufficient to elucidate the geographic origins of the proto- Malagasy. Some studies have reported that differences in physical appearance and culture between populations occupying different regions of the island may suggest different ancestral histories. In this study, we made use of information from three different genetic systems, namely mitochondrial DNA (mtDNA), the Y chromosome and several autosomal DNA markers to trace the origins of the males and females who contributed to the gene pool of the present-day Malagasy. We found that the mtDNA 9-bp deletion was present, throughout the island, at a total frequency of 22.5%. The 1.1 kb mtDNA control region was sequenced from 228 Malagasy individuals from which one hundred and twenty four unique mtDNA types, defined by 151 nucleotide changes were derived. Studies have shown that when the 9-bp deletion is used in conjunction with mtDNA control region sequence variation, the 9-bp deletion is a useful marker to trace population affinities. We were able to demonstrate that an overall Asian to African contribution of approximately 2:1 is indicated in present-day Malagasy populations. We used the Y Ala polymorphism (YAP) in conjunction with M9 to distinguish between African and non-African Y chromosomes. Overall, an African contribution of 78.2% and a non-African contribution of 21.85% was calculated. To gain insight into the autosomal DNA found in the Malagasy, we made use of three loci with population specific alleles (Sbl9.3, AT3id and APO-4) and the human mannose binding protein. Again, we observed both African and Asian affinities in the various Malagasy ethnic groups. By jointly analysing all the marker systems that were used, we were able to demonstrate a close relationship between ethnic groups from the different geographic regions on the island, and found the Malagasy to be a relatively homogeneous population. To test the ethnic and geographical structure present on the island, we conducted an analysis of molecular variance (AMOVA). These tests showed little biological support in favour of such hierarchies. A correlation analysis showed that very weak correlations exist between the data generated by the different genetic systems. Furthermore, by vividly demonstrating the differential input from males and females to the present-day Malagasy, this study also illustrates the advantages of combining mtDNA data with Y chromosomal results from the same individuals.Item The influence of cultural dimensions on entrepreneurial intention in Madagascar's rural areas(2014-07-10) Ratsimanetrimanana, Fenosoa A.Understanding the triggers of the intention was, is and will be at the heart of scholars’ preoccupations when dealing with the universe of entrepreneurship. This unique pioneering research aimed at comparing the Malagasy main ethnic groups in terms of measures of cultural dimensions and perceived desirability and examining the effects of this perceived desirability on the relations between cultural dimensions and entrepreneurial intention. A non-experimental cross-sectional survey, based on a cluster sampling with quota approach comprising three sub-samples of ethnic groups and a structured questionnaire directly administrated by trained interviewers, was the source of data of the research. The use of relevant robust statistical tests characterised the data processing of the research, which revealed that there is no important difference in the measures of cultural dimensions among main ethnic groups in Madagascar’s rural areas. The level of perceived desirability and the relationships between cultural dimensions and entrepreneurial intention are not importantly moderated by perceived desirability among the main ethnic groups in Madagascar’s rural areas. Furthermore, it has been discovered that to some extent, Madagascar would not be a country of ethnic diversity and beginning to understand the Malagasy entrepreneurial profile based on cultural dimension, perceived desirability and entrepreneurial intention is possible. Within the context of an unprecedented level of poverty of the population of Madagascar, which strangles the way to a harmonious and sustainable development, the findings of the research would make an invaluable contribution to the setting up or the refining of policies and strategies targeting the promotion of entrepreneurship in general and self-employment in particular. It is broadly acknowledged that the key to alleviating poverty is based on the encouragement of self-employment of all individuals.