A building classification scheme of housing stock in Malawi for earthquake risk assessment

Abstract

This study presents a building classification scheme for residential houses in Malawi by focusing upon informal construction, which accounts for more than 90% of housing in the country with the highest urbanisation rate in the world. The proposed classification is compatible with the Prompt Assessment of Global Earthquakes for Response (PAGER) method and can be used for seismic vulnerability assessments of building stock in Malawi. To obtain realistic proportions of the building classes that are prevalent in Malawi, a building survey was conducted in Central and Southern Malawi between 10th and 20th July 2017. The results from the survey are used to modify the PAGER-based proportions of main housing typologies by reflecting actual housing construction in the surveyed areas. The results clearly highlight the importance of using realistic building stock data for seismic risk assessment in Malawi; relying on global building stock information can result in significant bias of earthquake impact assessment.

A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: active fault and seismogenic source databases for southern Malawi

“…In this study, we first describe the South Malawi Active Fault Database (SMAFD), which is a systematic attempt to map active faults and collate their geomorphic attributes in southern Malawi. Located within the East African Rift System (EARS), southern Malawi lies in a region specifically highlighted by Styron and Pagani (2020) as a priority area for future active fault mapping; population growth in this region as well as seismically vulnerable building stock is also driving an increased exposure to seismic hazard (Tectonic Shift RIFT2018 Report, 2019Goda et al, 2016;Hodge et al, 2015;Kloukinas et al, 2020;Ngoma et al, 2019;Novelli et al, 2019).…”

Seismic fragility models for typical non-engineered URM residential buildings in Malawi

“…For each façade, a set of URM material properties is assigned in a probabilistic manner. In particular, façades that belong to the same building are characterised by different mechanical parameters to take into account the variability of construction quality within the same construction [12]. The probabilistic distributions from which the random properties are extracted are based on experimental tests of local URM materials [19], as discussed in Section 3.…”

“…Regarding structural vulnerability, the study emphasised that the adoption of global empirical models [10,11] may lead to potential bias and significant variation in the prediction of collapse rates. Moreover, the classification of the Malawian building stock through global building classes can be rather subjective and consequently uncertain and questionable [12]. More recently, the Global Earthquake Model (GEM) Foundation has released a new set of models for seismic risk assessment, including a global fragility/vulnerability database [13], a global hazard model [14], and an exposure database for different geographical regions, including East Africa [15].…”

“…1). In particular, by referring to the classification of Kloukinas et al [12], URMs with the following characteristics are considered ("UFB*" in [12]): (i) fired bricks in cement mortar assemblage, (ii) absence of timber/concrete lintels, (iii) light metal roof (no diaphragm action), (iv) rectangular plan shape, and (v) single storey.…”

A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: The South Malawi Active Fault Database

“…CC BY 4.0 License. increased exposure to seismic hazard (World Bank, 2019;Goda et al, 2016;Hodge et al, 2015;Kloukinas et al, 2019;Ngoma et al, 2019;Novelli et al, 2019). Notably, previous PSHA in the EARS has typically been conducted using the ~65 year long instrumental record of seismicity alone (Ayele, 2017;Goitom et al, 2017;Midzi et al, 1999;Poggi et al, 2017).…”