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Earthquake forewarning – A multidisciplinary challenge from the ground up to space

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Freund F.

Acta Geophysica

2013

tom Vol. 61, no. 4

775--807

Most destructive earthquakes nucleate at between 5-7 km and about 35-40 km depth. Before earthquakes, rocks are subjected to increasing stress. Not every stress increase leads to rupture. To understand preearthquake phenomena we note that igneous and high-grade metamorphic rocks contain defects which, upon stressing, release defect electrons in the oxygen anion sublattice, known as positive holes. These charge carriers are highly mobile, able to flow out of stressed rocks into surrounding unstressed rocks. They form electric currents, which emit electromagnetic radiation, sometimes in pulses, sometimes sustained. The arrival of positive holes at the ground-air interface can lead to air ionization, often exclusively positive. Ionized air rising upward can lead to cloud condensation. The upward flow of positive ions can lead to instabilities in the mesosphere, to mesospheric lightning, to changes in the Total Electron Content (TEC) at the lower edge of the ionosphere, and electric field turbulences. Advances in deciphering the earthquake process can only be achieved in a broadly multidisciplinary spirit.

Toward a unified solid state theory for pre-earthquake signals

100%

Freund F.

Acta Geophysica

2010

tom Vol. 58, no. 5

719-766

Many different non-seismic pre-earthquake signals have been reported but there is great uncertainty about their origin, their correlation to each other and to the impending seismic event. The discovery of stressactivated electric currents in rocks provides a possible explanation. Stresses activate electronic charge carriers, namely defect electrons in the oxygen anion sublattice, equivalent to O- in a matrix of O2-, also known as positive holes. These charge carriers pre-exist in unstressed rocks in a dormant, electrically inactive state as peroxy links, O3Si-OO-SiO3, where two O- are tightly bound together. Under stress dislocations sweep through the mineral grains causing the peroxy links to break. Positive holes, thus generated, flow down stress gradients, constituting an electric current with attendant magnetic field variations and EM emissions. The positive holes accumulate at the surface, creating electric fields, strong enough to field-ionize air molecules. They also recombine leading to a spectroscopically distinct IR emission seen in laboratory experiments and night-time infrared satellite images. In addition positive holes interact with radon in the soil, affecting the radon emanation.