Abstract:
Ionospheric response to the recent 25 April 2015 Gorkha, Nepal earthquake is studied in terms of Global Positioning System-Total
Electron Content (GPS-TEC) from the viewpoints of source directivity, rupture propagation and associated surface deformations, over
and near the fault plane. The azimuthal directivity of co-seismic ionospheric perturbations (CIP) amplitudes from near field exhibit excellent
correlation with east-southeast propagation of earthquake rupture and associated surface deformations. In addition, the amplitude
of CIP is observed to be very small in the opposite direction of the rupture movement. Conceptual explanations on the poleward directivity
of CIP exist in literature, we show the observational evidences of additional equator ward directivity, interpreted in terms of rupture
propagation direction. We also discuss the coupling between earthquake induced acoustic waves and local geomagnetic field and its
effects on near field CIP amplitudes. We suggest that variability of near field CIP over and near the fault plane are the manifestations of
the geomagnetic field-wave coupling in addition to crustal deformations that observed through GPS measurements and corroborated by
Interferometric Synthetic Aperture Radar (InSAR) data sets.
