KivuSNet: The First Dense Broadband Seismic Network for the Kivu Rift Region (Western Branch of East African Rift)

Single-Station Seismo-Acoustic Monitoring of Nyiragongo's Lava Lake Activity (D.R. Congo)

“…On the seismic spectrogram (Figure 8A), the secondary microseismic peak is clearly dominant between 0.1 and 0.3 Hz. Above 0.3 Hz, the continuous harmonic volcanic tremor is well-detected, preferentially below 1 Hz among all seismic stations of the KivuSNet network Oth et al, 2017) but it could be also detectable until 1.5 to 2 Hz as observed here for KBTI. Higher frequency contents until 4-5 Hz are discernable during night periods.…”

“…Congo, Rwanda, Burundi) regional network KivuSNet (see Oth et al, 2017 for more details about the network). This site is equipped with a broadband seismometer (Nanometrics Trillium Compact 120 s−100 Hz) and a smallaperture array (20 m) of three infrasound sensors manufactured by Boise State University (e.g., Johnson and Ronan, 2015).…”

“…Volcano-tectonic locations are obtained using a "picking-free" cross-correlation based technique adapted to low SNR events (see Barrière et al, 2017) and a simple low-resolution 1-D velocity model with two layers between 0 and 30 km depth for the Virunga Volcanic Province (VVP) (Mavonga et al, 2010). Precise hypocenter determination is adversely impacted by the use of this rough velocity model and relatively poor station coverage around the volcano (see Oth et al, 2017). A daily count is tabulated when at least 8 stations located in the VVP are available.…”

“…It is now well-known that variations of (near-) surface activity at active volcanoes, either effusive or explosive, can be efficiently monitored by analyzing the coupled infrasound and seismic signals (e.g., Matoza et al, 2009Matoza et al, , 2010Ichihara et al, 2012;Richardson and Waite, 2013;Ulivieri et al, 2013). The seismicity characteristics of Nyiragongo and, more generally, of the entire Virunga Volcanic Province (VVP), are not very well known because of the lack of a permanent, local monitoring infrastructure until recently (Pagliuca et al, 2009;Oth et al, 2017). There is very little knowledge of the seismic activity preceding the two last eruptions in 1977 and 2002, such as sequences of tremor and volcano-tectonic activity recorded by only two analog seismometers in [2001][2002], thus preventing the understanding and the detection of similar pre-eruptive processes (Kavotha et al, 2002;Komorowski et al, 2004).…”

“…The progressive deployment of a new local broadband seismic network, mostly between 2015 and 2017, has already provided some important and new insights into seismicity patterns accompanying Nyiragongo's activity Oth et al, 2017). These first studies have notably allowed for the detection and location of a continuous background, lowfrequency (<1 Hz) seismic tremor source at Nyiragongo volcano, most likely related to spattering activity of the persistent lava lake such as observed at Kilauea volcano (Patrick et al, 2016).…”