Non-Double-Couple Components in Moment Tensors of Aftershock Seismicity and Laboratory Earthquakes [thesis]

Eva Stierle, Universitätsbibliothek Der FU Berlin, Universitätsbibliothek Der FU Berlin
Recent developments in waveform data-acquisition technology in combination with improved methods of modelling of seismic waves have enabled us to study the details of physical processes in earthquake sources with an unprecedented accuracy. This has revealed that the common assumption that earthquakes represent shear faulting on a planar rupture in an isotropic Earth's crust is too simplistic and does not explain data adequately. The complexities of the earthquake process are, in particular,
more » ... enced by the presence of non- double-couple (non-DC) components frequently observed in seismic moment tensors. Early studies showed, however, that non-DC components are difficult to determine accurately being often contaminated by numerical errors. The non- DC components are sensitive to noise in the input data, to errors in the modelling procedure, to a velocity model, to an earthquake location and to the amount of data in terms of the focal sphere coverage. In addition, their physical origin covers a broad range of possibilities, which further complicates the interpretation of the non-DC components. Therefore, high- quality data with good focal sphere coverage and detailed knowledge of the medium are essential for determining reliable non-DC components. This thesis deals with the determination and error analysis of the non-DC components of seismic moment tensors. In the thesis, the state-of-the-art moment tensor inversion algorithms are refined and extensive synthetic tests are performed in order to study the uncertainties and resolvability of the non-DC components. By analysing high-quality waveform data of earthquakes on various scales, the non-DC components are retrieved and suggestions for their physical origin are given. On the field scale, the aftershock sequence of the Mw=7.4 1999 Izmit earthquake in northwestern Turkey is analysed. The analysed earthquake catalogue contains waveforms of more than 4000 relative relocated events observed at 35 three-component short-period seismic stations surrounding the rupture zo [...]
doi:10.17169/refubium-5156 fatcat:57opfyirmnfergu4lrawp6rwse