Time‐resolved study of charge generation and propagation in igneous rocks

Abstract

Abstract. Electrical resistivity changes, ground potentials, electromagnetic (EM), and luminous signals preceding or accompanying earthquakes have been reported many times, in addition to ground uplift and tilt and other parameters. However, no concept exists that would tie these diverse phenomena together into a physically coherent model. Using low-to medium-velocity impacts to measure electrical signals with microsecond time resolution, it is observed that when gabbro and diorite cores are impacted at relatively low velocities, --100 m/s, highly mobile charge carriers are generated in a small volume near the impact point. They spread through the rocks, causing electric potentials exceeding +400 mV, EM, and light emission. As the charge cloud spreads, the rock becomes momentarily conductive. When a granite block is impacted at higher velocity, --1.5 km/s, the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. After the sound waves have passed, the surface of the granite block becomes positively charged, suggesting the same charge carriers as observed during the lowvelocity impact experiments, expanding from within the bulk. which all nominally anhydrous minerals incorporate when crystallizing in H20-laden environments. The fact that positive holes can be activated by low-energy impacts, and their attendant sound waves, suggests that they can also be activated in the crust by microfractures during the dilatancy phase. Depending on where in the stressed rock volume the charge carriers are activated, they will form rapidly moving or fluctuating charge clouds that can account for earthquake-related electrical signals and EM emission. Wherever such charge clouds intersect the surface, high fields are expected, causing electric discharges and earthquake lights.

Ionospheric foF2 and TEC Anomalous Days Associated with M >= 5.0 Earthquakes in Taiwan during 1997-1999

“…However, this paper shows that the greatest chances of observing the decrease anomalies of the foF2 and TEC occur on the 4th days before the M ≥ 5.0 earthquakes under study. Although possible causal mechanisms are not fully understood (Bolt 1999;Freund 2000;Kim and Hegai 1999), we found that the lead time of anomalies to the M ≥ 6.0 earthquakes tends to be shorter than that to the M ≥ 5.0 earthquakes. Figure 3a depicts variations of the foF2 to be more fluctuated than those of the TEC.…”

Neural network based tomographic approach to detect earthquake-related ionospheric anomalies

“…Such a structure might provide a key to a possible solution to pre-seismic ionospheric anomalies. Recently, several mechanisms for lithosphere-atmosphere-ionosphere coupling, such as the atmospheric electric field, the atmospheric gravity wave (AGW), and gas emanation, have been proposed (Pulinets and Boyarchuk, 2004;Freund, 2000;Molchanov et al, 2006). If positive holes excited around the epicenter diffuse and outflow from the epicenter, an upward electric field is generated on the surface of the earth (Freund, 2000).…”

Preseismic lithosphere‐atmosphere‐ionosphere coupling

“…It has also been proposed that positively charged holes, associated with microfracturing prior to earthquakes, diffuse from the focal zone to the ground surface. There are laboratory experiments that sup port this possibility [Freund, 2000]. How ever, such preseismic electric fields on the ground followed by preseismic ionospheric anomalies have not yet been observed.…”