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Title: The relationship between intraplate earthquakes and temperature
Author: Emmerson, B.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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The thermal conductivity of mantle rocks is strongly dependent on temperature, and has been shown to have a significant effect on the modelled thermal structure of cooling oceanic plates. This dissertation models temperatures in subducting slabs, taking into account the temperature-dependence of the relevant physical parameters, and investigates the maximum temperatures, potential temperatures, and homologous temperatures up to which intraslab earthquakes occur. An analysis of the world’s subduction zones reveals that intraslab seismicity is consistent with being limited to material having potential temperatures less than 600 °C. Apparent exceptions to this pattern occur in regions where the Nazca Plate subducts subhorizontally beneath South America, with which the final study in this dissertation is concerned. The unusual subduction geometry in the Peruvian and Pampean segments of the South American subduction zone keeps the overriding plate and the subhorizontal subducting slab in contact for several hundreds of km. Thermal modelling including this unusual geometry shows the subducting slab to be relatively cold in these regions, as compared with typical subduction zones where more immediate contact with the mantle wedge results in a hotter slab temperature structure. In the Peruvian and Pampean regions, intraslab seismicity is found to occur at potential temperatures less than 600 °C. Furthermore, the continental mantle above the slab is shown to be cold enough to generate earthquakes. Teleseismic waveform-modelling is used to constrain 39 earthquake focal depths, and confirms that the continental mantle of Peru is indeed seismogenic.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available