Dependence of waveform of near-field coseismic ionospheric disturbances on focal mechanisms

Elvira Astafyeva,Kosuke Heki

doi:10.1186/bf03353206

Abstract

AbstractUsing Total Electron Content (TEC) measurements with Global Positioning System we studied ionospheric responses to three large earthquakes that occurred in the Kuril Arc on 04 October 1994, 15 November 2006, and 13 January 2007. These earthquakes have different focal mechanisms, i.e. high-angle reverse, low-angle reverse, and normal faulting, respectively. TEC responses to the 2006 and 2007 events initiated with positive and negative changes, respectively. On the other hand, the initial TEC changes in the 1994 earthquake showed both positive and negative polarities depending on the azimuth around the focal area. Such a variety may reflect differences in coseismic vertical crustal displacements, which are dominated by uplift and subsidence in the 2006 and 2007 events, respectively, but included both in the 1994 event.

Highlights

A large earthquake excites surface waves that go round the Earth several times, and body (P and S) waves that penetrate the core and reach the opposite side of the Earth
Total Electron Content (TEC) Response to the Earthquakes First we examine TEC responses to the 2006 earthquake, because this is the “typical” large event in subduction zones
The TEC responses to the 2007 earthquake, where the coseismic vertical movements were dominated by subsidence (Fig. 5(c)), were rather complicated

Summary

Introduction

A large earthquake excites surface waves that go round the Earth several times, and body (P and S) waves that penetrate the core and reach the opposite side of the Earth. Do the initial motion polarities of such ionospheric disturbances depend, like P-waves, on the earthquake focal mechanisms? Ionospheric disturbances after large earthquakes (Coseismic Ionospheric Disturbances, CID) are the superposition of perturbations by different origins such as coseismic vertical crustal movements (Calais and Minster, 1995; Afraimovich et al, 2001, 2006; Heki and Ping, 2005; Heki et al, 2006), propagating Rayleigh surface waves

Results

Conclusion