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| Titel |
Rupture Propagation Imaging of Fluid Induced Events at the Basel EGS Project |
| VerfasserIn |
Jonas Folesky, Jörn Kummerow, Serge A. Shapiro |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092500
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| Publikation (Nr.) |
 EGU/EGU2014-6851.pdf |
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| Zusammenfassung |
| The analysis of rupture properties using rupture propagation imaging techniques is a fast
developing field of research in global seismology. Usually rupture fronts of large to
megathrust earthquakes are subject of recent studies, like e.g. the 2004 Sumatra-Andaman
earthquake or the 2011 Tohoku, Japan earthquake. The back projection technique is the most
prominent technique in this field. Here the seismograms recorded at an array or at a seismic
network are back shifted to a grid of possible source locations via a special stacking
procedure. This can provide information on the energy release and energy distribution of the
rupture which then can be used to find estimates of event properties like location,
rupture direction, rupture speed or length. The procedure is fast and direct and it only
relies on a reasonable velocity model. Thus it is a good way to rapidly estimate
the rupture properties and it can be used to confirm independently achieved event
information.
We adopted the back projection technique and put it in a microseismic context. We
demonstrated its usage for multiple synthetic ruptures within a reservoir model of
microseismic scale in earlier works. Our motivation hereby is the occurrence of relatively
large, induced seismic events at a number of stimulated geothermal reservoirs or waste
disposal sites, having magnitudes ML ≥ 3.4 and yielding rupture lengths of several hundred
meters. We use the configuration of the seismic network and reservoir properties of the
Basel Geothermal Site to build a synthetic model of a rupture by modeling the wave
field of multiple spatio-temporal separated single sources using Finite-Difference
modeling.
The focus of this work is the application of the Back Projection technique and the
demonstration of its feasibility to retrieve the rupture properties of real fluid induced events.
We take four microseismic events with magnitudes from ML 3.1 to 3.4 and reconstruct
source parameters like location, orientation and length. By comparison with our synthetic
results as well as independent localization studies and source mechanism studies in this area
we can show, that the obtained results are reasonable and that the application of back
projection imaging is not only possible for microseismic datasets of respective
quality, but that it provides important additional insights in the rupture process. |
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