Acoustic emission events interpreted in terms of source directivity

0525378 - GFÚ 2021 RIV CH eng J - Journal Article
Kolář, Petr - Petružálek, Matěj - Lokajíček, Tomáš - Šílený, Jan - Jechumtálová, Zuzana - Adamová, Petra - Boušková, Alena
Acoustic emission events interpreted in terms of source directivity.
Pure and Applied Geophysics. Roč. 177, č. 9 (2020), s. 4271-4288. ISSN 0033-4553. E-ISSN 1420-9136
R&D Projects: GA ČR(CZ) GA16-03950S; GA ČR(CZ) GA18-08826S
Institutional support: RVO:67985530 ; RVO:67985831
Keywords : source directivity * Haskell source * acoustic emission * source mechanism inversion
OECD category: Environmental and geological engineering, geotechnics; Geology (GLU-S)
Impact factor: 2.335, year: 2020
Method of publishing: Limited access
https://link.springer.com/article/10.1007/s00024-020-02517-w

During inversion for the source mechanisms of laboratory acoustic emission events, relatively high misfit values (expressed as the RMS of the inverted equations) were observed. Our experiment was performed on Westerly Granite. A processed set of data consisting of 2405 acoustic emission events was used and a semi-homogeneous velocity model was considered. A correction for sensor radiation patterns and individual sensor constants was taken into account, and an acausal attenuation model was assumed. Source mechanisms were inverted for the moment tensor. The application of a more sophisticated medium model improved inversion quality only for some events. Introducing the source directivity, a standard approach for earthquakes with magnitudes larger than approximately 4, increased the number of successfully inverted events. Directivity was introduced using a Haskell source model. Optionally unilateral and bilateral versions of the source were considered. Lower values of RMS for the Haskell source model were considered to justify the directivity approach. This formalism enables us to select the preferable fault from the two nodal planes within the fault plane solution. The rupture directions were observed to tend to the dip direction of the preferred fault. They were found to be preferably subparallel to slip directions for acoustic emissions with a significant DC component. The source time functions retrieved from the seismograms are in agreement with finite source theory.
Permanent Link: http://hdl.handle.net/11104/0309535