Post-seismic ionospheric response to the 11 April 2012 East Indian Ocean doublet earthquake

Abstract

The 11 April 2012 East Indian Ocean earthquake is unique because of its largest ever recorded aftershock. The main earthquake occurred with a magnitude of 8.6 Mw and was followed by a strong aftershock (8.2 Mw). Our analysis of the main shock indicates that the rupture was a mixture of strike-slip and thrust faults, and significant vertical surface displacements were observed during the event. The prime interest here is to study the post-seismic ionospheric disturbances, along with their characteristics. As both earthquakes had large magnitudes, they provided an opportunity to minimize the ambiguity in identifying the corresponding seismic-induced ionospheric disturbances. Approximately 10 min after both seismic events, the nearby ionosphere started to manifest electron density perturbations that were investigated using GPS-TEC measurements. The epicenters of both events were located south of the magnetic equator, and it is believed that the varying magnetic field inclination might be responsible for the observed north-south asymmetry in the post-seismic total electron content (TEC) disturbances. These disturbances are observed to propagate up to approximately 1,500 km towards the north side of the epicenter and up to only a few hundred kilometers on the south side. The frequency analysis of the post-seismic TEC disturbances after both earthquakes exhibits the dominant presence of acoustic frequencies varying between approximately 4.0 to 6.0 mHz. The estimated propagation velocities of the post-seismic TEC disturbances during the main shock (0.89 km/s) and aftershock (0.77 km/s) confirm the presence of an acoustic frequency as the generative mode for the observed TEC fluctuations.

Coseismic Contortion and Coupled Nocturnal Ionospheric Perturbations During 2016 Kaikoura, Mw 7.8 New Zealand Earthquake

“…The disposition of CIP is normally explained invoking surface displacements either at the epicenter or along the rupture as their source (e.g., Astafyeva & Heki, ; Heki et al, ; Rolland et al, ; Sunil et al, , ). However, the Kaikoura earthquake rupture constitutes contributions from two thrust zones of CCTZ and KCTZ; the total rupture duration of ~100 s (Zhang et al, ) is lower than the characteristic period of acoustic waves (~4 min) in upper atmosphere.…”

Near-field co-seismic ionospheric response due to the northern Chile Mw 8.1 Pisagua earthquake on April 1, 2014 from GPS observations

“…Reddy and Seemala, 2015;Sunil et al, 2015;Cahyadi and Heki, 2015;Chum et al, 2012;Rolland et al, 2011a,b;Tsugawa et al, 2011;Galvan et al, 2011;Saito et al, 2011;Heki, 2011;). These ionospheric perturbations carry traceable information about the earthquake itself that generated them.…”

“…In addition to the magnitude of the earthquake and focal depth, there is some evidence that the earthquake focal mechanism , atmospheric acoustic resonance conditions (e.g. at 3.7 and 4.4 mH z , Nishida et al, 2000;Rolland et al, 2013;Sunil et al, 2015;Tahira, 1995), directivity and apparent velocity (Heki and Ping, 2005), geomagnetic latitude, and other factors, can influence the intensity of ionospheric responses. While some of these aspects are addressed by Cahyadi and Heki (2015) using 21 earthquakes between M w 6.6 and 9.2, TEC response amplitudes during quiet and disturbed geomagnetic conditions have been compiled by Perevalova et al (2014), which can serve as ready reference to seismo-ionospheric studies.…”

“…It is evident that dense GPS arrays such as Southern California Integrated GPS Network (SCIGN) (Calais et al, 2003), Japanese GPS Earth Observation Network (GEONET, operated by GSI, Japan, Sagiya, 2004;Ogawa et al, 2012) Sumatra GPS Array (SuGAr) (Sunil et al, 2015;Cahyadi and Heki, 2013;Cahyadi and Heki, 2015) provide an opportunity to investigate ionospheric perturbations and their spatio-temporal characteristics at higher resolution than any other currently available techniques (Saito et al, 2001). For earthquakes with magnitude M w $ 6, the signal-to-noise ratio of these perturbations is small and may show up just above the noise level.…”

Co-seismic ionospheric GPS-TEC disturbances from different source characteristic earthquakes in the Himalaya and the adjoining regions

“…But for Moderate earthquakes of magnitudes Mw from 5 to 5.9, the perturbations tend to become small (Ducic et al, 2003). It has been shown in the previous studies that dense GPS arrays can provide an opportunity to investigate ionospheric perturbations in the most efficient manner (Reddy, 2016;Reddy and Seemala, 2015;Seemala and Valladares, 2011;Ogawa et al, 2012;Sunil et al, 2015;Heki, 2013, 2015). Some advanced techniques, such as HF Doppler sounding (Artru et al, 2004;Ogawa et al, 2012), DEMETER (Ryu et al, 2014), Over-The-Horizon Radar (Occhipinti et al, 2010), Faraday rotation measurements using linearly polarized electromagnetic signals from geostationary satellites (Davies, 1980), and GPS (Ducic et al, 2003;Heki, 2011;Saito et al, 2011) have also shown that ionospheric plasma perturbations can be generated by large earthquakes.…”