Ionospheric disturbances triggered by the 25 April, 2015 M7.8 Gorkha earthquake, Nepal: Constraints from GPS TEC measurements

Coseismic Traveling Ionospheric Disturbances during the Mw 7.8 Gorkha, Nepal, Earthquake on 25 April 2015 From Ground and Spaceborne Observations

“…The initial positive phase observed in south of epicenter is further found to propagate with a supersonic velocity of ~2.39 km/s. This velocity of ~2.39 km/s observed in Figure is consistent with the reported velocities of 2.4 and 2.6 km/s by Reddy and Seemala () and Catherine et al (), respectively, for VTEC perturbations which they have attributed to Rayleigh wave. Further, Chen et al, () have shown that the Rayleigh wave‐induced perturbations in VTEC is ~1.6 km/s in the near field of 0–500 km epicentral distance, which is further increased to 2.35 km/s at 500–1,500 km and 2.74 km/s at 1,500–4,000 km in the far field.…”

“…They have further reported that the average propagation velocity of induced TEC perturbations due to shock acoustic wave and Rayleigh wave is ~1180 m/s and 2400 m/s, respectively. Catherine et al () have reported east‐west asymmetry in the initial arrival time of coseismic ionospheric TEC perturbations. They have also mentioned that the TEC perturbations are predominantly in the east and southeast directions and completely absent in the north of epicenter.…”

“…Recent studies have made early reports on the coseismic ionospheric disturbances observed from ground-based GPS receivers (Reddy & Seemala, 2015;Catherine et al, 2016;Sunil et al, 2017;Chen et al, 2016) and satellite observations (Sun et al, 2016) during this Nepal Gorkha earthquake over Indian subcontinent region. Reddy and Seemala (2015) have studied coseismic ionospheric TEC perturbations and reported that the induced TEC perturbations are due to two modes, namely, shock acoustic wave and surface Rayleigh wave-induced perturbations.…”

On the Co‐Seismic Ionospheric Disturbances (CIDs) in the Rapid Run Ionosonde Observations Over Allahabad Following Mw 7.8 Nepal Earthquake on April 25, 2015

“…It is found one-to-one correspondence between Doppler signal and seismic waves (e.g., Yuen et al, 1969). Catherine et al (2017) also have investigated the Nepal earthquake using GPS TEC observations and suggested that these Rayleigh wave induced acoustic waves are not propagated to northern latitudes but they propagated to southern latitudes which is in agreement with Reddy and Gopi (2015) but in contrast to Joshi et al (2017) modeling work. This can be overcome by using rapid run ionograms (high resolution) to study the infrasonic wave signatures in the ionograms.…”

“…This can be overcome by using rapid run ionograms (high resolution) to study the infrasonic wave signatures in the ionograms. We believe that if rupture propagation can be factored in SAMI2 model, the results could be similar to Catherine et al (2017). It is known that the near field that is excited by co-seismic vertical displacement propagates as acoustic waves and gravity waves in the ionosphere.…”