A mathematical model of lithosphere–atmosphere coupling for seismic events

Abstract

Significant evidence of ionosphere disturbance in connection to intense seismic events have been detected since two decades. It is generally believed that the energy transfer can be due to Acoustic Gravity Waves (AGW) excited at ground level by the earthquakes. In spite of the statistical evidence of the detected perturbations, the coupling between lithosphere and atmosphere has not been so far properly explained by an accurate enough model. In this paper, for the first time, we show the result of an analytical-quantitative model that describes how the pressure and density disturbance is generated in the lower atmosphere by the ground motion associated to earthquakes. The direct comparison between observed and modelled vertical profiles of the atmospheric temperature shows the capability of the model to accurately reproduce, with an high statistical significance, the observed temperature fluctuations induced by strong earthquakes.

On the Geomagnetic Field Line Resonance Eigenfrequency Variations during Seismic Event

“…Finally, it is worth noticing that the variation of f * does not show any dependence on earthquake magnitude (not shown). Such result agrees with Carbone et al [15], who demonstrated that the emission of a non-evanescent AGW, generating FLR variation, does not depend on the individual earthquake parameter alone, but on both the combination of the length of the fault, the PGA, the time duration of the EQ, etc (see dispersion relation in Carbone et al [15]), and the local atmospheric scale height.…”

“…Finally, in the case of the absence of a co-seismic AGW emission, no possible f * variations can be detected (10 case event, see Table 1). Such a hypothesis is confirmed by Carbone et al [15], showing that the atmospheric fluctuations excited by a generic seismic event on the top of the first layer of the atmosphere can be evanescent. In fact, depending on the characteristic parameters of the EQ (length of the fault, peak ground acceleration strong time duration and so on), a the propagation of the AGW up to the ionosphere can be prevented.…”

“…As a consequence any alteration in the ionospheric plasma density induces a variation in the corresponding eigenfrequency. Consequently, we do interpret the f * changes observed in our 28 EQ events (see Table 1) as caused by the ionospheric plasma density variation induced by the emission of a co-seismic AGW leading to a pressure gradient [15].…”

“…In 28 events, we found a clear sudden decrease of the magnetospheric FLR eigenfrequencies, while in 10 cases we did not find any f * variation. The proposed explanation is that the plasma density at the footprint of the field line magnetically connected to the EQ location was modified of about ∆ρ 15%, by a gradient pressure fluctuations ∇p den induced by a propagation of an AGW emitted during the EQ occurrence [15,16]. At low latitudes the magnetospheric field lines are fully surrounded by the ionosphere and the FLR eigenfrequencies, depending on both the magnetic field and the plasma density along the field line [19,31], is expected to decrease [23,26,32].…”

“…Searches for possible seismo-ionospheric effects were also performed before the earthquake by the satellite Interkosmos-19 operating at F-region altitudes, providing for the first time evidence for an increase of both the intensity of VLF noise, in the frequency range between 140 Hz to 15 kHz, and for disturbances of the electron density at a distance from the epicentres up to a few 1000 km [3,14]. More recently, Carbone et al [15], Piersanti et al [16] started the development of an analytical model of the coupling between lithosphere-atmosphere-ionosphere-magnetosphere to be submitted to detailed experimental verification (M.I.L.C.). In the M.I.L.C.…”