Two‐mode ionospheric response and Rayleigh wave group velocity distribution reckoned from GPS measurement following Mw 7.8 Nepal earthquake on 25 April 2015. Issue 8 (27th August 2015)

• Record Type: Journal Article
• Authors: Reddy, C. D.; Seemala, Gopi K.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 8(2015:Aug.)
• Page Start: 7049
• Page End: 7059
• Publication Date: 2015-08-27
• Subjects: Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021502
• Languages: English
• ISSNs: 2169-9380

Abstract

<abstract abstract-type="main" id="jgra52020-abs-0001"> <title>Abstract</title> <p>The coseismic‐induced ionospheric total electron content (TEC) perturbations were analyzed following the <italic>M<sub>w</sub></italic> 7.8 Nepal earthquake (28.147°N, 84.708°E; depth ~15 km) that occurred on 25 April 2015 at 06:11:26 UTC. The ionospheric response is due to both the modes, i.e., shock acoustic waves (slow mode) and Rayleigh wave induced (fast mode). The continuous Global Positioning System (GPS) data at about 60 sites from various GPS networks have been used in the present study. All the sites within epicentral distance of ~2400 km and 70°–170° azimuth recorded the Rayleigh wave‐induced TEC response, while the sites within ~400–2200 km in the same azimuth recorded the response from both the modes. The maximum coseismic‐induced peak‐to‐peak TEC amplitude is ~1.2 total electron content unit, 1 TECU = 10<sup>16</sup> el m<sup>−2</sup>. From Hodochron plot, the apparent Rayleigh wave velocity has been determined as ~2400 m/s on the average and the acoustic wave velocity as 1180 m/s, both these waves being discernible beyond ~1200 km of epicentral distance as also evident from Hodochron plot and wavelet spectrographs. We reckoned the Rayleigh wave group velocities using ionospheric response at selected radial pairs of stations and validated. The ionospheric response distribution seen mainly depending on the epicentral distance, satellite geometry, directivity of radiation pattern, and the upper crustal heterogeneity. This study highlights the characteristics of ionospheric response consequent to the 2015 Nepal earthquake.</p> </abstract>