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Reference Events in sub-Saharan Africa and expected improvements from AfricaArray

Reference Events in sub-Saharan Africa and expected improvements from AfricaArray. Andy Nyblade, Rick Brazier, and Angela Marie Larson Pennsylvania State University, USA Paul Dirks and Ray Durrheim, University of Witwatersrand Lindsay Linzer, Council for Scientific and Industrial Research

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Reference Events in sub-Saharan Africa and expected improvements from AfricaArray

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  1. Reference Events insub-Saharan Africa and expected improvements from AfricaArray Andy Nyblade, Rick Brazier, and Angela Marie Larson Pennsylvania State University, USA Paul Dirks and Ray Durrheim, University of Witwatersrand Lindsay Linzer, Council for Scientific and Industrial Research Gerhard Graham, Council for Geoscience

  2. Location accuracy criteriaBondar et al (2003)

  3. Sub Saharan African Seismicity (M > 3) and Stations 1997-2007 (IRIS catalog) Outline Examples of previous event studies and problems with producing reference events New opportunities for developing GT

  4. Previous studies with M≥4Hofstetter and Beyth (2003) Standard catalog seismicity (1960-2000) and focal mechanisms using moment tensor inversions and first motion polarities Poor locations - events are typically not well relocated

  5. Previous studies with M≤3Keir et al (2006) EAGLE deployment (2001-2003) Good event location with many events probably meeting GT criteria BUT, most events are too small (M≤3) to be of interest regionally

  6. A few successesGT Events in Ethiopia and Tanzania

  7. GT5 (Local) Ethiopian events Tanzanian From project event catalogs Ethiopia: 256 events Tanzania: 2500 events Resulting in only 8 GT events

  8. Opportunities for new reference eventsTemporary deployments Tanzania 1994-1995 South Africa Seismic Experiment (SASE) 1997-1999 Ethiopia/Kenya 2000-2002 EAGLE 2001-2003 Cameroon 2005-2007

  9. Afar Deployments Ethiopia, UK, and USA joint deployment Fissure eruption with ongoing seismicity Large local/regional network is being installed

  10. Cameroon1/2005-1/2007Penn State, Washington U., IRGM (Cameroon) and University of Yaounde I (Cameroon) Two local events from the first year of the deployment with m>4 Work in progress to develop a catalog of local events from both years

  11. AfricaArray - A public-private partnership supporting capacity building and research linked to Africa’s natural resource sector • to support in-situ training and research programs to help build a scientific workforce --initially in geophysics • As part of the training and research programs, create a network of shared scientific observatories (initially broadband seismic stations) to promote education, research, and community building “AfricaArray” = array of training programs + array of research projects + array of partnerships and collaborations + array of scientific observatories

  12. AfricaArray Backbone Network 24 BB stations 6/07 28 BB stations by 12/07 24-bit data loggers Variety of BB sensors Data recovery 70-80% Data retrieval: S. Africa - daily Elsewhere - monthly

  13. An example of a GT event recorded by AA stations • Itezhi-Tezhi, Zambia • Installed Jan. 2006 • Guralp 3T sensor • RefTek data logger • Mozambique Earthquake • 22 February, 2006 • Mw 7.0 TEZI, Zambia Vertical ground displacement

  14. AfricaArrayTemporary Networks Congo Craton - Industry 2007-2010 PIRE - NSF 2007-2010 Mine network - DOE 2007-2010, then part of AA backbone

  15. Data for creating new reference events • In-mine networks • AA surface mine network • AA backbone stations

  16. AfricaArray - creating opportunities for reference events • Combine data from permanent and temporary stations • Using data from the mine network and permanent (backbone) stations For more information, please visit the AfricaArray web site: www.africaarray.psu.edu or come to the annual AfricaArray workshop (July 17, 18, 2007, Jburg)

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