Near-seismic effects in ULF fields and seismo-acoustic emission: statistics and explanation

Abstract

Part of Special Issue "Precursory phenomena, seismic hazard evaluation and seismo-tectonic electromagnetic effects"Abstract. Preseismic intensification of fracturing has been investigated from occurrence analysis of seismo-acoustic pulses (SA foreshocks) and ULF magnetic pulses (ULF foreshocks) observed in Karimshino station in addition to seismic foreshocks. Such analysis is produced for about 40 rather strong and nearby isolated earthquakes during 2 years of recording. It is found that occurrence rate of SA foreshocks increases in the interval (−12, 0 h) before main shock with 3-times exceeding of background level in the interval (−6, −3 h), and occurrence probability of SA foreshocks (pA∼75%) is higher than probability of seismic foreshocks (ps∼30%) in the same time interval.ULF foreshocks are masked by regular ULF activity at local morning and daytime, nevertheless we have discovered an essential ULF intensity increase in the interval (−3, +1 h) at the frequency range 0.05-0.3 Hz. Estimated occurrence probability of ULF foreshocks is about 40%. After theoretical consideration we conclude: 1) Taking into account the number rate of SA foreshocks, their amplitude and frequency range, they emit due to opening of fractures with size of L=70-200 m (M=1-2); 2) The electro-kinetic effect is the most promising mechanism of ULF foreshocks, but it is efficient only if two special conditions are fulfilled: a) origin of fractures near fluid-saturated places or liquid reservoirs (aquifers); b) appearance of open porosity or initiation of percolation instability; 3) Both SA and ULF magnetic field pulses are related to near-distant fractures (r<20-30 km); 4) Taking into account number rate and activation period of seismic, SA and ULF foreshocks,it is rather probable that opening of fractures and rupture of fluid reservoirs occur in the large preparation area with horizontal size about 100-200 km.

On Es-spread effects in the ionosphere connected to earthquakes

“…1, the number of Es-spread observations is presented as function of the local time for "background" and "seismoactive" days separately. The seismo-active time interval of the two hours before midnight is in agreement with the results of the observation of ULF-fields connected with earthquakes (Molchanov et al 2004(Molchanov et al , 2005. By Molchanov et al (2004Molchanov et al ( , 2005) ULF variations of the magnetic field are found in the frequency region of 0.05-0.2 Hz.…”

“…By Molchanov et al (2004Molchanov et al ( , 2005) ULF variations of the magnetic field are found in the frequency region of 0.05-0.2 Hz. The authors of the present work suggest that the increase of the Es-spread phenomena before earthquakes is caused by an enhanced activity of acoustic pulses with frequencies of the order of 0.05 Hz, which propagate from the region of earthquake preparation up into the atmosphere and ionosphere.…”

Lithosphere-atmosphere-ionosphere coupling as governing mechanism for preseismic short-term events in atmosphere and ionosphere

“…A question arises immediately: what means earthquake preparation process in a large zone order of hundred kilometers as it is followed from abovementioned observational facts and from observation of nearseismic effects (e.g. Molchanov et al, 2004c)? It is evident that conventional seismology theories (nucleation, dilatancydiffusion, dilatancy instability, consolidation and so on) have failed to explain neither our results, nor seismic data itself (absence of large stress accumulation and dilatancy, existence of deep EQs etc.…”

TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece

“…(Svets et al, 2004;Biagi et al, 2003;Crowley and McCrea, 1988;Afraimovich, 2000); ii) Local such as atmospheric or underground explosions, volcanoes, extreme weather phenomena (Calais et al, 1998;Jacobson and Carlos, 1988;Afraimovich et al, 2000); iii) Earthquakes (Afraimovich et al, 2001;Molchanov et al, 2004;Molchanov et al, 2005;Meister et al, 2002;Liperovsky et al, 2002;Shvets et al, 2004).…”