Double-Difference Seismic Event Relocation: A Study of the Applications and Limitations of the Relocation Problem

Biegel, Katherine M.

Double-Difference Seismic Event Relocation: A Study of the Applications and Limitations of the Relocation Problem

dc.contributor.advisor	Dettmer, Jan
dc.contributor.author	Biegel, Katherine M.
dc.contributor.committeemember	Eaton, David W. S.
dc.contributor.committeemember	Gilbert, Hersh Joseph
dc.contributor.committeemember	Innanen, Kristopher A. H.
dc.contributor.committeemember	Kao, Honn
dc.date	2024-11
dc.date.accessioned	2024-08-14T18:39:26Z
dc.date.available	2024-08-14T18:39:26Z
dc.date.issued	2024-08-12
dc.description.abstract	Earthquake relocation provides refined earthquake catalogs based on additional considerations or data beyond the initial earthquake location estimates. Double-difference relocation, in particular, utilizes the assumption that ray paths in close proximity to one another will pass through a similar earth velocity structure. The method minimizes the residual difference for pairs of these travel time observations to refine event locations. This thesis focuses on the application of three double-difference methods based on differing geometries of data pairing: event-pair relocation, station-pair relocation, and double-pair relocation. In this thesis, I introduce a previously unavailable software, relocDD-py, that implements all three of these relocation methods along with a complete workflow, including data preparation, automated variable selection, and post-relocation uncertainty analysis. This software is developed in Python using many widely implemented Python packages to allow for integration into existing seismic workflows. In addition, I present studies that apply this software and methodology at various scales, including (1) a large-scale tectonic study of complex plate subduction and the resulting seismicity in Alaska and Yukon where we find direct evidence of the Totschunda-Fairweather Connector fault; (2) a regionally observed induced seismicity event with analysis of the entire earthquake sequence from Peace River, Alberta where we find activation of multiple sub-parallel faults; and finally (3) a densely monitored induced seismicity experiment which ruptured a complex network of pre-existing faults near Fox Creek, Alberta where we find limits on the depth of seismicity to the hydraulic fracturing depth. Double-difference relocation can improve existing catalogs even in sparsely monitored areas and can reduce relative location uncertainty to such a degree that detailed three-dimensional interpretation of fault structures is possible. In many cases, event-pair relocation, the most widely applied double-difference method, is sufficient to improve relative uncertainties and maintain absolute location uncertainties. However, in cases with complex velocity models and dense monitoring, the double-pair method can improve relative uncertainties beyond event-pair relocation, which may identify additional seismicity features. The double-pair method is more computationally expensive and, therefore, is not necessary in all cases. All three double-difference relocation methods have an important role to play in earthquake and other seismic event relocation and catalog refinement. My work provides a software tool and a standardized workflow for the implementation of double-difference relocation in seismic studies.
dc.identifier.citation	Biegel, K. M. (2024). Double-difference seismic event relocation: a study of the applications and limitations of the relocation problem (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/119410
dc.language.iso	en
dc.publisher.faculty	Science
dc.publisher.institution	University of Calgary
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	seismology
dc.subject	earthquakes
dc.subject	tectonics
dc.subject	induced seismicity
dc.subject	earthquake source studies
dc.subject	earthquake location
dc.subject.classification	Geophysics
dc.title	Double-Difference Seismic Event Relocation: A Study of the Applications and Limitations of the Relocation Problem
dc.type	doctoral thesis
thesis.degree.discipline	Geoscience
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.