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Title: Earthquake source properties in the Hellenic and Aleutian Islands' subduction zones
Author: Liakopoulou, Fotini
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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This thesis provides information on earthquake source properties for recent, moderate-sized (5.5 < mb < 6.5) earthquakes in the Hellenic and Aleutian subduction zones. This is achieved through the analysis of teleseismic observations from the Global Digital Seismograph Network. The relative amplitude method of Pearce and Rogers is used to determine source orientations for all events studied, placing constraints on fault plane solutions typically to better than 5' in angle. This method is able to compute well-constrained solutions even when P-wave first motion polarity cannot be read unambiguously, because it includes polarity and amplitude information for phases other than direct P. Body-wave modelling is carried out to determine other earthquake source parameters including depth, seismic moment, seismic source dimensions, rupture velocity and stress drop. Broadband seismograms (recovered from short-period records) are used because they give a more complete representation of the source radiation for moderate-sized earthquakes than do conventional short- or long-period records. A two-dimensional finite dislocation model is used in the calculation of the synthetic seismograms. This model gives a more realistic representation of the earthquake source than does the point-source model. A plane-layer velocity structure both at the source and the receiver areas is assumed. Seven earthquakes associated with the Hellenic subduction zone are studied. Thrust components are present in the solutions for most events, in agreement with the overall compressional stress regime of the subduction zone. However, strike-slip components are found in events associated with transform faults identified by geological, morphological and seismic data. Forward body-wave modelling is carried out for three of these events. Seven earthquakes associated with the Aleutian Islands subduction zone are also studied. Most are found to have thrust mechanisms and fault strikes consistent with coupling of the lithospheric plates. One earthquake occurred in the oceanic crust beneath the trench, and is characterized by normal faulting with the tensional axis perpendicular to the arc. Solutions for other events are found to include a strike-slip component, consistent with local variations in deformation (e.g. adjacent to the Amlia fracture zone). One earthquake was situated within the upper part of the double Benioff zone beneath the Kamchatka peninsula. The down-dip direction of compression suggested by the orientation of the P-axis for this event is consistent with unbending stressed in the upper half of the subducting lithosphere. Body-wave modelling is carried out for five of these events.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available