Seismic source mechanism extended for rupture propagation estimate: a chance for the fault identification?

0488247 - GFÚ 2018 RIV CL eng C - Konferenční příspěvek (zahraniční konf.)
Šílený, Jan
Seismic source mechanism extended for rupture propagation estimate: a chance for the fault identification?
Proceedings of the Ninth International Symposium on Rockbursts and Seismicity in Mines. Santiago: Editec S.A., 2017 - (Vallejos, J.), s. 133-139. ISBN 978-956-7356-07-2.
[RaSim9. International Symposium on Rockbursts and Seismicity in Mines /9./. Santiago (CL), 15.11.2017-17.11.2017]
Grant CEP: GA ČR(CZ) GA16-03950S
Institucionální podpora: RVO:67985530
Klíčová slova: alternative to moment tensor * shear-tensile crack * radiation directivity * joint inversion * direction of rupture propagation * rupture speed
Obor OECD: Volcanology

The mechanism is an inherently point-source attribute of seismic source focus containing no information on the rupture propagation. The traditional description by the moment tensor offers little chance to absorb additional parameters related to finite-extent focus. Its alternative - the shear-tensile crack - is advantageously more flexible thanks to the fact that it is a physical model. It is the simplest extension of the traditional pure shear-slip model represented by complementing it with a phenomenon describing an opening or closing within the focal zone. This is achieved by allowing a deviation of the slip off the fault plane. As extreme cases of the oblique slip, the model involves both the pure shear and the tensile crack. Technically, its advantage is a smaller number of parameters needed for its description: there are 5 parameters only, i.e. one parameter less than for an unconstrained moment tensor. A smaller number of parameters is an advantage in the inverse process, expressed in its greater robustness, which is important especially in sparse monitoring configurations. For this reason and thanks to a grid search approach to the inverse task, we can optimize additional parameters during the search for the mechanism. The rupture velocity vector modifying the radiation pattern by the directivity effects is the first one at hand. We search for its direction constrained to lie within the fault plane marked by the mechanism. The speed of the rupture is considered either as fixed or free parameter. The grid search applied allows a detailed mapping of the model space with the advantage of constructing the confidence regions of all the source parameters involved – related both to the mechanism and to the rupture propagation. In this way, the error of the determination of the individual features of the source can be estimated.
Trvalý link: http://hdl.handle.net/11104/0282857