The processes leading to the growth and inhibition of equatorial anomaly before major earthquake (EQ) were viewed in this paper by examining global Total Electron Content (TEC) that contoured over longitude sectors covering Africa to Pacific, in association with EQ events of Japan (M = 9) that occurred at 135°E to 145°E and 35°N to 40°N, on March 9 and 11, 2011 and of Indonesia (M = 8.6) that took place at 2.311°N, 93°E, in April 11, 2012. The paper focuses on the development of abnormal increase in density in the night sector around—10° latitude zone prior to the two major EQ events, though their epicenters are separated widely from the anomaly region. The F-layer density variations from relevant locations and TEC features obtained from GPS at Appleton anomaly crest station are utilized as supporting inputs. The possible sources leading to the anomalous development in density are discussed in the frame of EQ time consequences of lithospheric-atmospheric processes between the equator and beyond. The role of electric field generated by pre EQ preparatory activities and dynamical coupling modes through seismic fault line are brought in to the ambit of discussion.

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<p>The role of orographic factors in modifying atmospheric dynamics on the background of an impending earthquake (EQ) that might lead to propagation of a signal beyond the Line Of Sight (LOS) is examined in the paper. The analysis is based on the data of anomalous reception of VHF FM-signal at Gauhati University (GU, 26.15°N, 91.66°E), a station located in the sub Himalayan terrain. The signal reception records show that their anomalous appearance are associated closely with earthquake events of M &gt;5.0, a phenomenon identified as EQ precursor. To identify sources of such reception, the paper presents some analytical approaches involving the terrain factors, impending EQ and atmospheric variabilities. Finally, the contribution of location/topography of the transmitter, receiver and epicenter in modifying the EQ induced atmospheric factors, is brought in to the ambit of analysis for explaining the observed over horizon VHF signal propagation. A special reference is made on the EQ time drop in temperature, increase in humidity and hence modification in Radio Refractive Index (RRI) gradient, in favoring such reception. A model in support of the observation on EQ time lithosphere-atmosphere coupling relevant to widening of radio horizon limit is also proposed.</p>

Amongst a number of precursory features in the atmosphere observed through Electro Magnetic (EM) techniques, the variabilites of the lower and upper atmosphere are considered to have yielded reasonably satisfactory results, though reliabilities as nowcasting are yet to be ascertained . Of recent interest in such studies are the waves and undulations possibly generated by Earth Quake (EQ) preparatory processes. Even with number of studies taken up in relevance to this issue, more inputs are necessary to make comprehensive views of generation process of such waves with special reference to an impending EQ . Under this background the paper presents analysis of Total Electron Content (TEC) and Scintillation from GPS observation at Guwahati in identifying generation of waves prior to an earthquake for realizing Lithosphere -Troposphere -Ionosphere (LTI) coupling dynamical status caused by EQ preparatory processes. The anomalous appearance of satellites from beyond the normal Line of Sight (LOS) prior to an EQ and their positions analyzed through respective azimuthal status ( with PRN in each case) are finally utilized in identifying the sources associated with generation of waves. The role of EQ induced tropospheric parameters as Radio Refractive Index (RRI) and Effective Earth Radius are brought in to the ambit of discussions.