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Title: Moment tensors for teleseismically recorded earthquakes
Author: Bowers, David
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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P waveforms from small intraplate earthquakes observed at teleseismic distances often exhibit discrete arrivals which are easily interpreted in terms of a direct P phase and associated surface reflections. These arrivals contain information about the P and S radiation pattern at the source. This thesis attempts to quantify how much information about the source is contained in seismograms from small disturbances. In the first study, regional surface waves and P waves recorded at teleseismic distances by short period (SP), long period (LP) and broadband (BB) seismographs are analysed to determine the source parameters of the Völkershausen seismic disturbance of 13 March 1989. This disturbance is the source of some controversy, with many proposed source mechanisms, including a shallow multiple mine collapse. Application of the relative amplitude method and forward modelling of the P waveforms recorded at teleseismic distances suggest that the data are consistent with a sub-vertical normal dip slip fault striking northwest-southeast at a depth of 6.5 km. Forward modelling of the surface waves recorded by the Blacknest broadband network shows that the observed surface waves are consistent with this source model. Examination of SP seismograms from the French network and waveforms from the Gräfenberg array, in the distance range 100 to 500 km, show no large Rg phase, which would be expected for a shallow mine collapse. In a second study, over 50 small earthquakes in the 1976 Gazli sequence were analysed based on SP array station recordings. Pearce et al (1980) studied 21 of these earthquakes using the relative amplitude method (Pearce 1977, 1980), assuming an a priori double couple source, and found that the observed waveforms were consistent with 45° reverse dip slip faults striking northwest-southeast.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available