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Workshop Earthquakes: Ground-based and Space Observations

Workshop Earthquakes: Ground-based and Space Observations. AN ELECTROMAGNETIC PROCESS REGULATES EARTHQUAKE ACTIVITY. Gerald Duma Central Institute for Meteorology and Geodynamics Vienna, Austria. Studies performed. 10-year research pogramme Several cooperations in Europe,

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Workshop Earthquakes: Ground-based and Space Observations

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  1. WorkshopEarthquakes: Ground-based and Space Observations AN ELECTROMAGNETIC PROCESS REGULATES EARTHQUAKE ACTIVITY Gerald Duma Central Institute for Meteorology and Geodynamics Vienna, Austria

  2. Studies performed • 10-year research pogramme • Several cooperations in Europe, Asia, America • Effect verified for many earthquake zones worldwide • Plausible interpretation and model

  3. Observations (1996) – daily range AUSTRIAM  2.5, 1901-1990 Geomagnetic Observatory

  4. Observations (1997) – daily range Mt. VESUVIUS volcanic eqs, area 10 x 10 km , 1.8  M3.1, 1972-1996, 1400 events Duma, Vilardo (INGV), 1998 Geomagnetic Observatory

  5. A seismic daily cycle • Aristoteles • Pliny the Elder,  79 A.D. eruption of Mt.Vesuvius • Tams, 1926 • Conrad, 1932 • Shimshoni, 1972 • Lipovics, 2000, 2005 • Schekotov & Molchanov, 2005 • Poorly investigated in recent decades, no interpretation given yet

  6. A seismic daily cycle 3 sub-periods 20th century AUSTRIA M  2.5 May 31 – June 18, 1997 Earthquake swarm in Austria, region IMST

  7. A seismic daily cycle • Observed in many main seismic regions • Earthquakes M  5 and M  6 • A very powerful geodynamic process acting!

  8. Observations (1996) – long term AUSTRIAM  3.1 (Io  5°) Obs WIK, comp N ‚ secular variation‘ Geomagnetic Observatory

  9. Mechanism, models? • Dependence on Local Time  Process related to sun • A mechanism which penetrates the whole Earth‘s lithosphere • Tides ?  No! • High energy mechanism • Can a few nT influence tectonic performance?

  10. The electromagnetic model • Geomagnetic variations in a conductive lithosphere • Maxwell‘s equations (E-H) • ‚Telluric currents‘ associated with all natural geomagnetic variations (frequency range from min – solar cycle)

  11. The electromagnetic model • Telluric currents and forces F = e . [ ve . B ] F ... mechanic force vector e ... electron charge ve ... velocity vector B ... magnetic field vector ‚Lorentz force‘ ve e B F

  12. The electromagnetic model • Magnetic observatories monitor: H(t) ~ IH(t) ~ FV(t) vertical force

  13. The electromagnetic model • Regional mechanic moment, torque Tr P1 P2 r I2 ≠ I1

  14. The electromagnetic model • The gradient of H(t) reflects the change of regional torque Tr(t) (azimuth Az) P Torque axis

  15. Energy – diurnal variation • The dayside Sq induced lithospheric current vortex (Chapman, Bartels, 1940; Matsushita, 1968) A large scale current field, covering  1/3 of the northern Earth‘s hemisphere T = MM x H

  16. Energy – diurnal variation • The mechanic moment of Sq for a single loop (Duma, Ruzhin, 2003) The example demonstrates: The deformation energy provided to the lithosphere by a single current loop, radius 1500 km and current 10 kA, is equivalent to the energy of an earthquake M 5,1.

  17. Energy – diurnal variation • 60% of total moment concentrates in a 30° segment H I

  18. Modelling the electromagnetic effect • Data for H(lat,long) to compute gradient • Daily variation: hourly mean values • Model of Sq telluric current vortex • Regional observatory data (lati, longi) • Long term: annual mean values • Retrieved from IGRF, 1900-2010 (grid data) • Regional observatory data (lati, longi)

  19. Case studies – Regions Austria Taiwan California Baikal region

  20. Case studies – Austria(M ≥ 3.2, Gradient H – N10W) Diurnal range Long term Gradient H from IGRF10 (1900-2010) Gradient H from Sq-Model 1900 - 2003

  21. Case studies – Taiwan(M ≥ 5, Gradient H – N55E) Diurnal range Long term Gradient H from IGRF10 (1900-2010) Gradient H from Sq-Model 1973 - 1998

  22. Case studies – Baikal area(M ≥ 5, Gradient H – N00E) Diurnal range Long term Gradient H from Sq-Model Gradient H from IGRF10 (1900-2010) 1900 - 1980 2001 - 2006

  23. Case studies – California(M ≥ 6, Gradient H – N30E) Diurnal range Long term Gradient H from IGRF10 (1900-2010) Gradient H from Sq-Model 1970 - 2005

  24. Case study – earthquakes 2004-2006 2004 08 01 – 2006 12 31, M  5 IONIAN IS S-ITALY AEGEAN

  25. Case study – earthquakes 2004-2006 1965 – 1989 (25 yrs, PDE) Gradient H (N85E) IONIAN ISLANDS Seismic activity – Local Time M  5 1990 – 2003 (14 yrs, PDE) 2004 08 01 – 2006 12 31 M  5 n = 11 (PDE)

  26. Case study – earthquakes 2004-2006 1910 – 1980 (72 yrs, INGV) S-ITALY Seismic activity – Local Time M  5 2004 08 01 – 2006 12 31 M  4.5 n = 11 (PDE) 2004 08 01 – 2006 12 31 M  5 n = 4 (PDE)

  27. Case study – earthquakes 2004-2006 Aegean Sea Aegean Sea vs. Crete Seismic activity – Local Time M  5 2004 08 01 – 2006 12 31 M  5 n = 4 (PDE) Aegean Sea / Strongest events 2004-2006: 2006 01 08 UT=113455.64 lat=36.31°long=23.21°d=66 km M=6.7 Crete 2004 08 01 – 2006 12 31 M  5 n = 5 (PDE)

  28. Case study – earthquakes 1963-2006 Aegean M  4, n = 956 (NOA) AEGEAN vs. IONIAN IS Seismic activity – long term M  4 Gradient H from IGRF10 Ionian Is M  4, n = 237 (NOA)

  29. Case study – earthquakes 1963-2006 S-Italy M  5, n = 57 (INGV+PDE) S-ITALY vs. IONIAN IS Seismic activity – long term M  5 Ionian Is M  5, n = 36 (NOA)

  30. Novel aspects • External sources – causing geomagnetic variations - strongly influence seismic activity (trigger) • Origins: solar radiation, ionosphere, Sq ; magnetic dynamo • Answer to daily rhythm of seismic activity (LT) • Monitoring the process: easy by geomagnetic observatories • Predictability: systematic diurnal, seasonal, secular variations (IGRF 2010) • Not yet investigated: influence of magnetic storms • Faster monitoring of variations by space observations ?

  31. Observations (1997) – long term Mt. VESUVIUS volcanic eqs, area 10 x 10 km , 1.8  M3.1, 1972-1996, 1400 events Duma, Vilardo (INGV), 1998 Duma, Vilardo (INGV), 1998 n: annual number of eqs M  1.8, 1972-1996 sf: annual number of solar flares (103)

  32. Tectonic settings & faulting mechanisms in Greece (Dewey et al., 1973 / A. Tzanis, UOA, 2003)

  33. Model of Sq telluric current vortex • Fits observed Sq-variations at observatories • Computes grad H(LT)

  34. H – current density

  35. The electromagnetic model • Magnetic observatories monitor horizontal force FhC (t)

  36. Energy – diurnal variation • Sq: solar controlled, heating, ionization, tides(Chapman, Bartels, 1940)

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