Physical vulnerability assessment and household preparedness of Buea Municipality to seismic hazards from Mount Cameroon Eruptions: A cause for concern

Abstract

Earthquakes associated with volcanic eruptions from Mount Cameroon can impact society and building infrastructures. This study  therefore aimed to assess the following: i) the geological features (rock/soil types) and its characteristics in selected localities within Buea  municipality; ii) past-eruption/earthquake impact assessment on buildings; iii) physical vulnerability of buildings infrastructure and  iv) household preparedness to earthquake hazards. The study utilized a mixed-method approach, combining quantitative and qualitative  techniques. Geological characteristics was assessed through site visits across the selected ten localities by physical observation and rock  sample collection. Past-eruptions (1959, 1982, 1999, 2000) impacts assessment on buildings and household preparedness to earthquakes  were evaluated using structured questionnaires. Building vulnerability was assessed using the ENSURE and the Building Vulnerability  Index (BVI) methodology on the following parameters: building state, building materials, house position (single, row, clustered), house  age, proximity to volcano and the surrounding soils/rocks. Findings revealed the rock types are predominantly made up of basaltic rocks/ lava, pyroclastic deposits, tuff, lahar deposits and brownish to black loamy soils. Earthquake impact on buildings from the 4 eruptions  revealed that localities around the epicenter were the most affected. Physical vulnerability assessment revealed that 35 % of the  vulnerable buildings were < 5 years old and were residential buildings. Quantitative analysis of building vulnerability indicated moderate  vulnerability to seismic hazards in 50 % of the assessed localities. For household preparedness to volcanic earthquakes: 32.0 % of  households had first aid kits and 73.1 % had identified safe evacuation locations. The study revealed that the presence of tuff, soft and  loose unconsolidated soils; the position and state of buildings; and the absence of evacuation plans significantly contributed to seismic  vulnerability in Buea municipality.