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Slow-moving landslides exhibit persistent but non-uniform motion at low rates which makes them exceptional natural laboratories to study the mechanisms that control the dynamics of unstable hillslopes. Here we leverage 4.5+ years of satellite-based radar and optical remote sensing data to quantify the kinematics of a slow-moving landslide in the tropical rural environment of the Kivu Rift, with unprecedented high spatial and temporal resolution. We measure landslide motion using sub-pixel image correlation methods and invert these data into dense time series that capture weekly to multi-year changes in landslide kinematics. We cross-validate and compare our satellite-based results with very-high-resolution Unoccupied Aircraft System topographic datasets, and explore how rainfall, simulated pore-water pressure, and nearby earthquakes control the overall landslide behaviour. The landslide exhibited seasonal and multi-year velocity variations that varied across the landslide kinematic units. While rainfall-induced changes in pore-water pressure exerts a primary control on the landslide motion, these alone cannot explain the observed variability in landslide behaviour. We suggest instead that the observed landslide kinematics result from internal landslide dynamics, such as extension, compression, material redistribution, and interactions within and between kinematic units. Our study provides, a rare, detailed overview of the deformation pattern of a landslide located in a tropical environment. In addition, our work highlights the viability of sub-pixel image correlation with long time series of radar-amplitude data to quantify surface deformation in tropical environments where optical data is limited by persistent cloud cover and emphasize the importance of exploiting synergies between multiple types of data to capture the complex kinematic pattern of landslides.

The East African Rift System (EARS) is an active continental rift zone that hosts a diverse range of processes that result in recent and ongoing crustal deformation. To analyze these processes, we used Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) to complement the sparse GNSS velocity field with high resolution measurements of line-of-sight (LOS) deformation between 2015 and 2022. A broad survey approach was employed to detect new signals within the central section of the EARS, and to establish a baseline for future studies focused on tectonic, volcanic, and/or hydrologic deformation and change spanning geodetic time scales. With this regional approach, we were able to resolve signals varying over time-spans of a few weeks to several years that have magnitudes greater than ∼1 cm/yr. Our resulting deformation field shows a diverse range of signals related to the processes listed above as well as other unknown sources. This includes up to 8.5 cm/yr of groundwater-related subsidence in Nairobi, up to 70 cm of LOS displacement during the eruption of Nyiragongo in 2021, and steady uplift in the Manyara basin with a rate of 2.8 cm/yr. We update previously published InSAR measurements of Mount Suswa volcano, and the geothermal fields in Olkaria. We also show LOS change ranging between 2 and 5 mm/yr over a distances of approximately 200 km spanning the Kenya Rift with the greatest differential rates occurring south of Lake Turkana. More generally, our results highlight the ambiguity of relying solely on the sparse network of GNSS for studies such as those characterizing tectonic motion and rift opening. Such studies are likely missing many important signals and/or includes sites that are contaminated with signals unrelated to the target process. • InSAR complements the GNSS velocity field in the EARS, revealing high-resolution LOS deformation between 2015 and 2022. • Identified a diverse range of volcanic, tectonic, and anthropogenic deformation signals. • Illuminated the limitations of sparse GNSS networks for comprehensive deformation analysis. [ABSTRACT FROM AUTHOR]

We present an overview of the installation, operation, and initial results of the 15-station KivuGNet (Kivu Geodetic Network) in the Kivu Region, Central Africa. The network serves primarily as a research and monitoring tool for active volcanic, earthquake, and plate boundary processes in the region. Continuous operation of in-situ measurement networks in naturally and politically harsh environments is challenging, but has proven fruitful in this case. During the operation of the network since 2009, KivuGNet has captured: co-eruptive deformation from two eruptions of Nyamulagira (in 2010 and 2011–2012); inter-eruptive deformation, which we interpret as a combination of plate motion across the Western – East Africa Rift, and decreasing deep-seated magma accumulation under the Nyiragongo-Nyamulagira region; co-seismic deformation from the M w 5.8 August 7, 2015 Lwiro earthquake at the western border of Lake Kivu. We hope that this study will serve as a motivation for further implementation of in-situ geodetic networks in under-monitored and under-studied sections of the East African Rift. [ABSTRACT FROM AUTHOR]

In the frame of the Belgian GeoRisCA multi-risk assessment project focusing on the Kivu and northern Tanganyika rift region in Central Africa, a new probabilistic seismic hazard assessment has been performed for the Kivu rift segment in the central part of the western branch of the East African rift system. As the geological and tectonic setting of this region is incompletely known, especially the part lying in the Democratic Republic of the Congo, we compiled homogeneous cross-border tectonic and neotectonic maps. The seismic risk assessment is based on a new earthquake catalogue based on the ISC reviewed earthquake catalogue and supplemented by other local catalogues and new macroseismic epicenter data spanning 126 years, with 1068 events. The magnitudes have been homogenized to Mw and aftershocks removed. The final catalogue used for the seismic hazard assessment spans 60 years, from 1955 to 2015, with 359 events and a magnitude of completeness of 4.4. The seismotectonic zonation into 7 seismic source areas was done on the basis of the regional geological structure, neotectonic fault systems, basin architecture and distribution of thermal springs and earthquake epicenters. The Gutenberg-Richter seismic hazard parameters were determined by the least square linear fit and the maximum likelihood method. Seismic hazard maps have been computed using existing attenuation laws with the Crisis 2012 software. We obtained higher PGA values (475 years return period) for the Kivu rift region than the previous estimates. They also vary laterally in function of the tectonic setting, with the lowest value in the volcanically active Virunga – Rutshuru zone, highest in the currently non-volcanic parts of Lake Kivu, Rusizi valley and North Tanganyika rift zone, and intermediate in the regions flanking the axial rift zone. [ABSTRACT FROM AUTHOR]

The study of rift basin's morphology can provide good insights into geological features influencing the development of rift valleys and the distribution of volcanism. The Kivu rift segment represents the central section of the western branch of the East African Rift and displays morphological characteristics contrasting with other rift segments. Differences and contradictions between several structural maps of the Kivu rift make it difficult to interpret the local geodynamic setting. In the present work, we use topographic and bathymetric data to map active fault networks and study the geomorphology of the Kivu basin. This relief-based fault lineament mapping appears as a good complement for field mapping or mapping using seismic reflection profiles. Results suggest that rifting reactivated NE-SW oriented structures probably related to the Precambrian basement, creating transfer zones and influencing the location and distribution of volcanism. Both volcanic provinces, north and south of the Kivu basin, extend into Lake Kivu and are connected to each other with a series of eruptive vents along the western rift escarpment. The complex morphology of this rift basin, characterized by a double synthetic half-graben structure, might result from the combined action of normal faulting, magmatic underplating, volcanism and erosion processes. [ABSTRACT FROM AUTHOR]