Earthquke-related variation in Schumann Resonance (SR) spectra and Q-bursts as simulated with a global TDTE Network

Abstract:

The monitoring of earthquakes with SR has been reported by Nickolaenko and Hayakawa (Nickolaenko and Hayakawa 2014, 2006, Hayakawa 2005). Despite the presence of many SR observatories globally, the observation of SR anomalies caused by earthquakes is rare. And the physical mechanism for the SR anomaly is not clear. Further attention to methods for observing SR anomalies caused by earthquakes is needed. A simulation approach based on Nelson’s 2DTelegraph Equation (TDTE) Network (Nelson, MIT doctoral thesis, 1967) is developed. The Earth-ionosphere cavity is discretized into 24×24 tesserae. This network approach is more flexible than an analytical model, especially for a model with day-night asymmetry. The relation of the magnitude of the anomaly and the geometrical arrangement among source, receiver and disturbed zone is discussed for the uniform model. The perturbed zone size is computed according to the estimated size of the earthquake preparation zone. For example, the radius of the perturbed zone is about 1000km when the earthquake magnitude is about Ms=7.0. The intensity variations for the first four SR modes are compared between perturbed and unperturbed models. In addition, the spectral characteristics at different distances between source and disturbed zone are analysed. Interestingly, the electric field shows different variation than the magnetic field in response to the localized perturbation. For the uniform model with single Q-burst source, when the height of the local ionosphere is decreased, the electric field is increased and reaches nearly 50% in intensity in the perturbed zone in the uniform model. However, in contrast, the magnetic response is far less pronounced. It shows almost no variation. But for multisource excitation, the electric field and magnetic field both show dramatic response which reaches nearly 100% variation for some special modes. And the big variation is not restricted to the perturbed zone. The variations show complicated relationships with the different geometrical arrangements among three sources and receivers.