澳大利亚Gawler克拉通的大地电磁测深研究.pdfVIP

Magnetotelluric survey in Gawler Craton – Musgrave Seismic Acquisition Processing team Jingming Duan, Peter Milligan, Aki Nakamura, Jenny Maher, Josef Holzschuh, Ross Costelloe, Tanya Fomin, Leonie Jones Nov 2010 GOMA Seismic and MT workshop, Nov 2010 Acknowledgements • Russell Korsch, Richard Blewett, Narelle Neumann Geoscience Australia • Graham Heinson, Kate Selway, Stephan Thiel The University of Adelaide • Australian Government Onshore Energy Security Program for funding • Geodynamic Framework Project of Geoscience Australia • ANSIR/AuScope for MT equipment GOMA Seismic and MT workshop, Nov 2010 Outline • Magnetotelluric (MT) method • GOMA MT survey overview • Acquisition system and parameters • Data processing and analysis • MT survey preliminary results GOMA Seismic and MT workshop, Nov 2010 MT Definition • Magnetotelluric (MT) is a passive electromagnetic (EM) sounding technique • Measure variation in Earth’s natural electrical (E) and magnetic (B) fields in time series • Ratio of E / B use to derive resistivity distribution of Earth’s crust and upper mantle • Frequency range 10 kHz to 0.0001 Hz (0.0001 s to 10000 s) • Investigation depths of tens of metres to hundreds of kilometre GOMA Seismic and MT workshop, Nov 2010 MT Source Field • High frequencies 1 Hz from Spherics - Lightning (thunderstorm) activity world-wide • Low frequencies 1 Hz from - Interaction between solar wind and magnetosphere • Vary with periods on seconds, minutes, hourly, daily, yearly cycles GOMA Seismic and MT workshop, Nov 2010 Depth of Investigation • The depth of investigation depends upon frequenc