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Title: Exploiting F Statistics from Array Seismograms for Characterising Earthquake and Explosion Sources
Author: Heyburn, Ross
ISNI:       0000 0001 3555 6656
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2007
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In this thesis, two applications of the F-detector (a processing technique that under certain conditions optimally detects correlated signals crossing an array of seismometers) are described and tested. In the first application, the F trace and its associated probability theory, are used to place uncertainty bounds on the signal-to-noise ratios of P and the depth phases pP and sP arriving on short-period P seismograms recorded at teleseismic distances. The relative amplitude metho~ is often used to determine focal mechanisms that are compatible with the observed relative amplitudes of P, pP and sP. Here upper and lower signal-to-noise ratio bounds on P, pP and sP, calculated using the F trace and its associated probability, are used as the input for the relative amplitude method. This method is tested on several well-studied earthquakes and is found to be effective for earthquakes deeper than around 15 km. The F trace and its associated probability can also be used to help identify depth phases on P seismograms recorded at teleseismic distances, and hence estimate earthquake depth. A method of processing seismic array data to calculate F probability traces which optimally highlight candidate depth phases is developed. The F probability traces are then converted from functions of delay time relative to P, into functions of source depth. These can then be combined for a network of stations to give a single trace which can be interpreted in terms of source depth. This method allows earthquake depths for small-to-medium sized earthquakes to be estimated quickly and with minimal analyst input. The method is applied to a series ofearthquakes located in a range of tectonic environments, it is effective for many of the earthquakes analysed here with body-wave magnitudes greater than approximately 4.0, and depths greater than around 10 km. However in regions where the geological structure is complex (e.g., island arcs), the method gives mixed results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available