We performed an integrated analysis of the coseismic slip, afterslip and aftershock activity of the 2014 M_w8.1 Pisagua earthquake. This earthquake seems to be spatially located between two major historical earthquakes, the 1868 M_w8.8 earthquake in southern Peru and the 1877 M_w8.5 earthquake in northern Chile. Continuous GPS data were used to model the coseismic slip of the mainshock and the largest aftershock (M_w7.6). The afterslip was modeled for 273 days (end of year 2014) after the largest aftershock, revealing two patches of afterslip: a southern patch between the mainshock and the largest aftershock and a patch to the north of the mainshock. Observations from the seismic network indicate that aftershocks were concentrated near the southern patch. Conversely, the northern patch contained hardly any aftershocks, indicating a dominant aseismic slip. The Pisagua earthquake occurred within a prominent, curved section of the Andean subduction zone. This section may have acted as a barrier for the largest historical earthquakes and as an isolated segment during the Pisagua earthquake.

To unravel the relationship between earthquake and tsunami using ionospheric total electron content (TEC) changes, we analyzed two Chilean tsunamigenic subduction earthquakes: the 2014 Pisagua M_w 8.1 and the 2015 Illapel M_w 8.3. During the Pisagua earthquake, the TEC changes were detected at the GPS sites located to the north and south of the earthquake epicenter, whereas during the Illapel earthquake, we registered the changes only in the northward direction. Tide-gauge sites mimicked the propagation direction of tsunami waves similar to the TEC change pattern during both earthquakes. The TEC changes were represented by three signals. The initial weaker signal correlated well with Acoustic Rayleigh wave (AW_Rayleigh), while the following stronger perturbation was interpreted to be caused by Acoustic Gravity wave (AGW_epi) and Internal Gravity wave (IGW_tsuna) induced by earthquakes and subsequent tsunamis respectively. Inevitably, TEC changes can be utilized to evaluate earthquake occurrence and tsunami propagation within a framework of multi-parameter early warning systems.

The quantity and accuracy of satellite-geodetic measurements have increased over time, revolutionizing the monitoring of tectonic processes. Global Navigation Satellite System (GNSS) and satellite radar signals provide observations beyond ground deformation, including how earthquake and tsunami processes affect variations in the ionosphere. Here, we study the Hunga Tonga Hunga Ha’apai (HTHH) volcanic eruption 2022 and its associated tsunami propagation with the analysis GNSS derived Total Electron Content (TEC), Synthetic Aperture Radar (SAR) Sentinel-1 data, complemented with tide gauge observations. We utilize GNSS sites data within a ~ 5000 km radius from the volcanic eruption for estimating the ionospheric perturbation as Vertical TEC. We give evidence on the detection of acoustic gravity, internal gravity, and atmospheric Lamb waves signatures in the TEC perturbation. In particular, the internal gravity waves that concentrated in the southwest of Tonga, directly correlates with the observed tsunami propagation direction as accounted by the tide gauge measurements. However, the acoustic gravity wave signature in the TEC is dominant in the north direction suggesting a surface deformation, which could be verified using Sentinel-1A SAR amplitude data. The analysis presented herein shows that within 5 h of the volcanic eruption, the central part of the HTHH island landscape disappeared with the biggest explosion. The unprecedented detail resolved by integrating satellite data yields previously unknown details of the deformation of the 2022 HTHH volcano eruption.

The impact of total solar eclipse of July 2, 2019 on the Ionosphere is studied using 24 Chilean GPS stations north–south of the totality path. The total solar eclipse passed through Coquimbo region from ~ 16:38 CLT (~ 20:38 UTC) to ~ 16:40 CLT (~ 20:40 UTC) and maximum eclipse was observed ~ 16:39 CLT (~ 20:39 UTC). The total electron content (TEC) derived from GPS signals shows peculiar features. At the totality stations TEC variations are small (~ 0.39 TECu), but it shows significant decrease (maximum ~ 2.24 TECu) for stations located south and increase (maximum ~ 3.89 TECu) for the stations located north of totality of the surface. The wavelet analysis of VTEC timeseries shows the presence of strong atmospheric gravity waves (AGWs) of duration ~ 30 to 60 min at the stations located north of totality. Thus, the results suggest an interplay between eclipse effect on the ionosphere plasma density and eclipse generated AGWs induced plasma density perturbation provided the peculiar features.

This study investigates the ionospheric responses to two successive geomagnetic storms that occurred on 7–8 and 10–11 October 2024 over the Indian equatorial and low-latitude sector. Using GNSS-derived vertical total electron content (VTEC) measurements and the Global Ionosphere Map (GIM)-derived VTEC variation, supported by O/N₂ ratio variations, equatorial electrojet (EEJ) estimates, and modeled equatorial electric fields from the Prompt Penetration Equatorial Electric Field Model (PPEEFM), the distinct mechanisms driving storm-time ionospheric variability were identified. The 7–8 October storm produced a strong positive phase in the morning sector, with VTEC enhancements exceeding 100 TECU, followed by sharp afternoon depletions. This short-lived response was dominated by prompt penetration electric fields (PPEFs), subsequently suppressed by disturbance dynamo electric fields (DDEFs) and storm-induced compositional changes. In contrast, the 10–11 October storm generated a more complex and prolonged response, including sustained nighttime enhancements, suppression of early morning peaks, and strong afternoon depletions persisting into the recovery phase. This behavior was mainly controlled by DDEFs and significant reductions in O/N₂, consistent with long-lasting negative storm effects. EEJ variability further confirmed the interplay of PPEF and DDEF drivers during both events. The results highlight that even storms of comparable intensity can produce fundamentally different ionospheric outcomes depending on the dominance of electrodynamic versus thermospheric processes. These findings provide new insights into storm-time ionospheric variability over the Indian sector and are crucial for improving space weather prediction and GNSS-based applications in low-latitude regions.