Interpretation of Microseismic Events of Large Magnitudes Collected at Cooper Basin, Australia and at Basel, Switzerland

Mukuhira, Yusuke and Nozaki, Hyuma and Asanuma, Hiroshi and Niitsuma, Hiroaki and Wyborn, D. and Häring, Markus O. (2010) Interpretation of Microseismic Events of Large Magnitudes Collected at Cooper Basin, Australia and at Basel, Switzerland. In: Proceedings World Geothermal Congress 2010. International Geothermal Association.

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Abstract

The authors analyzed microseismic events of large magnitudes collected during and after hydraulic stimulations at Cooper Basin, Australia in 2003 and at Basel, Switzerland in 2006. The characteristics of the large events and their similarity/difference to the neighboring events were evaluated using hypocentral distribution and source radius, similarity of waveforms, fault plane solutions and volumetric strains induced by microseismic events. It was found that some of the large events at Cooper Basin brought clear extensions of the seismic cloud into previously seismically silent zones suggesting that some kind of hydraulic barrier was broken by the large events. These events can be interpreted by single asperity slips in existing fractures. Meanwhile, it was revealed that most of the large events from the middle and deeper parts of the stimulated zone at Basel, where many hypocenters of other microseismic events can be seen, occurred as a result of the shear slip of multiple asperities. Shallow, large events at Basel whose hypocenters were estimated to be spatially independent from the seismic cloud, are very likely to occur in fractures sub-parallel to the stimulated zone. The mechanism of the large events is not universal and may depend on the site. The triggering mechanism of the large events remains unidentified.

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Item Type: Book Section
Additional Information: Congress held April 25-30, 2010, in Bali, Indonesia
Uncontrolled Keywords: HDR/EGS, microseismicity, stimulation, magnitude, Cooper Basin, Basel
Subjects: Methodology > Method and procesing > Collective properties of seismicity
Region > Australia > Copper Basin
Region > Switzerland > Basel
Inducing technology > Geothermal energy production
Project: SHEER project > COOPER BASIN: geothermal energy injection experiment