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Titel: Inversion for local stress field inhomogeneities
Sonstige Titel: Inversion nach lokalen Spannungsinhomogenitäten
Sprache: Englisch
Autor*in: Reinhardt, Jörg
Schlagwörter: Bebenschwarm; Spannungsinversion; Marienbader Störung; Marienbader Verwerfung; Novy Kostel; Marianske Lazne Fault; Eger Graben; earthquake swarm; stress inversion; Vogtland/NW-Bohemia
GND-Schlagwörter: Spannungstensor; Spannung <Geologie>; Schwarmbeben; Vogtland; Spline-Interpolation; Eger Graben; Interpolation; NURBS; Marienbad
Erscheinungsdatum: 2007
Tag der mündlichen Prüfung: 2007-05-22
Zusammenfassung: 
In this thesis, the 1997 Vogtland/NW-Bohemia swarm has been selected for the
analysis of inhomogeneities in the stress field because two predominant
nearly perpendicular flat zones of seismicity are visible in the hypocentre
distribution implying inhomogeneities in the stress field. This is unusual
compared to other swarms originating from this area. An existing dataset of
waveform data, P- and S-phase picks, and master event locations has been
analysed regarding similarity of waveforms, location refinement, and
estimation of relative moment tensors. The latter are used together with a
regional dataset of 50 single focal mechanisms and 125 focal mechanisms from
the 2000 hydraulic fracturing experiment at the KTB for an estimate of the
regional homogeneous and the locally inhomogeneous stress field.

An automated processing procedure consisting of coherence analysis,precise
relocation, relative moment tensor inversion, and stress trajectory
determination has been set up. The coherence analysis has been successfully
applied using a new method that uses three component seismograms. 457 events
are separated into 13 multiplets of similar waveforms of at least size 8.
Another result are precise relative arrival time measurements which are fed
into the precise relocation program "hypoDD". Two nearly perpendicular
structures are found in the hypocentre distribution. 352 moment tensors are
estimated using a relative moment tensor inversion. Three different algorithms to distinguish between fault plane and auxiliary plane are
successfully applied to them. A regional homogeneous stress inversion using
the focal mechanisms of the single events and selected events from the other
datasets has been applied yielding (azimuth/plunge) sigma1=(147°/9°),
sigma2=(10°/78°), and sigma3=(238°/8°). The dense population of moment
tensors for the 1997 swarm inside a volume of aproximately 1 km^3 has been
systematically subdivided using a moving box technique. A locally homogeneous
stress inversion has been applied to each subset that consists of at least 10
measurements. The resulting deviatoric stress tensors are arranged on a
regular grid and their components are smoothed using Non Uniform Rational
B-Splines (NURBS) depending on three spatial parameters. The resulting sigma1
and sigma3 trajectories are visualised by projecting part of them into the The plane structures derived from the hypocentre distribution are consistent
with the fault planes that have been selected from moment tensors and with
the patterns found in the stress trajectories. Neutral points regarding the maximum and minimum horizontal stresses, sigmaH and sigmah, respectively,are
identified. The results of this work support the model of fluid induced seismicity and migrating fluids.
URL: https://ediss.sub.uni-hamburg.de/handle/ediss/1781
URN: urn:nbn:de:gbv:18-33491
Dokumenttyp: Dissertation
Betreuer*in: Dahm, Torsten (Prof. Dr.)
Enthalten in den Sammlungen:Elektronische Dissertationen und Habilitationen

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