Ionospheric response following the M_w 7.8 Gorkha earthquake on 25 April 2015

Abstract

A detailed observation of the coseismic ionospheric disturbances (CIDs) after the Mw 7.8 Gorkha earthquake has been carried out using total electron content (TEC) data from 333 GPS stations. This inland earthquake occurred on 25 April 2015, at a depth of ~15 km. Following the quake at 6:11 UT, groups of CIDs were observed from 06:18 to 07:00 UT. The CIDs we observed could be classified into three groups: CIDs related to gravity waves (GWs), CIDs related to acoustic waves (AWs), and CIDs related to seismic Rayleigh surface waves. The GW‐related CIDs traveled at a velocity of ~500 m/s. They were mainly observed to the south and north of the epicenter, within 600 km of the event, with a maximum amplitude of 0.18 total electron content unit (TECU; 1 TECU = 1016 el m−2). The AW‐related CIDs traveled at a velocity of ~700–1400 m/s. They could be observed for 1000 km in all directions from the epicenter, with an amplitude of ~0.3 TECU. The CIDs related to Rayleigh waves could be observed only to the east of the epicenter, at a maximum distance of 1800 km. They had an apparent velocity of ~2.0–2.3 km/s. Through comparing the seismogram data from Incorporated Research Institutions for Seismology to the TEC data, we found that the azimuthal characteristics of the ground vibrations agree with the directivity of the CIDs related to Rayleigh surface waves.

Depletion and Traveling Ionospheric Disturbances Generated by Two Launches of China's Long March 4B Rocket

“…This might occur due to the north-south geomagnetic field ( Figure 5) strongly inhibiting the eastward/westward propagation of ionized particles. The north-south asymmetry propagated TIDs are found in many TEC observation of TIDs, for example, Calais et al (2002), Heki and Ping (2005), Astafyeva et al (2011), andLiu et al (2017), and are primarily due to the inclination of the geomagnetic field. As the rockets are moving in the ionosphere, the launch-induced ionospheric disturbances could strongly be influenced by the geomagnetic field immediately after ignition.…”

“…To avoid multipath signals and the possible errors from converting the sTEC to the vTEC, we used only TEC observations with elevations greater than 30° . For a more detailed process, please refer to Calais and Minster (), Mannucci et al (), Ding et al (), Yue et al (), Xiong et al (), and Liu et al ().…”

Relating Far‐Field Coseismic Ionospheric Disturbances to Geological Structures

“…In this work, a single-layer ionosphere model was used, and the height of the layer was set to 350 km. More detailed information about the data processing can be found in Liu et al (2017) and Liu et al (2018).…”

“…Differences in these parameters can be partly related to the varied velocities of Rayleigh surface waves in different regions. In addition, seawater around epicenters is also a factor that can cause differences between inland earthquakes and submarine earthquakes and is topic of ongoing research (Inchin et al, 2020(Inchin et al, , 2021Liu et al, 2017). The impact of geological structures on far-field CIDs is understudied, particularly for inland earthquakes.…”

Chinese ionospheric investigations in 2016–2017

“…Liu HT et al (2017) carried out a detailed observation of the coseismic ionospheric disturbances (CIDs) after the M w 7.8 Gorkha earthquake by using TEC data from 333 GPS stations. This inland earthquake occurred on 25 April 2015, at a depth of ~15 km.…”