A review of the seismicity of the Cameroon Volcanic Line observed by two
local seismic networks
Abstract
The Cameroon Volcanic Line (CVL) is a linear feature of volcanism that
begins off the western coast of Africa with several islands and
continues on shore through Cameroon further into the African continent.
Equatorial Guinea’s Bioko Island is the largest and last of the CVL
volcanic islands. It is home to three shield volcanoes: Pico de Basile,
Pico Biao, and Gran Caldera de Luba. Eruptive history is only known for
Pico de Basile which erupted within the past 100 years, and steam vents
were observed as recently as 2012. There is no permanent seismic
monitoring; the closest seismic stations are in Cameroon and have not
reported data since 2015. The CVL is of scientific interest and has been
studied by several groups. Most geophysical studies focus on the area
around Mt. Cameroon, the most active volcano in the system. A network of
seismic stations was installed across the entire country from 2005-2007.
There has been no successful geophysical surveys of the island portion
of the line. In Nov-2017 Drexel University, supported by the Bioko
Biodiversity Protection Program (BBPP) and the Universidad Nacional de
Guinea Ecuatorial (UNGE), installed 4 broadband seismometers on Bioko.
Two stations were installed in March of 2019.Preliminary earthquake
detection and location was completed with an automated STA/LTA
algorithm. Initial locations use the global IASP91 model and events were
relocated with a local model. Events cluster in two areas: those near
Bioko Island and those near Cameroon. Between 12-Dec-2017 and
17-Feb-2018, 77 events were recorded. Local magnitudes range between
0.16and 2.61. Of these events, 49 are located near Cameroon and 28 are
near Bioko. Most of the depths are upper to mid-crust. Analysis of the
entire data set yields 458 events with 367 near Bioko Island and 91 near
Cameroon. The range in local magnitude is -0.28 – 3.86. Our preliminary
results show seismicity associated with Bioko Island as well as
Cameroon. Locations match well with events recorded by the regional
network previously installed in Cameroon. In addition, the rate of
seismicity recorded from2017-2019 is comparable to what was observed
from the Cameroon network when distance is taken into account. Data has
been retrieved in Feb-2018, Nov-2018, and Mar-2019. The next service was
scheduled Mar-2020 but the trip was canceled due to travel restrictions.