Seismic Risk Assessment of Urban and Rural Settlements around Lake Malawi

Goda, Katsuichiro; Gibson, Emily Daisy; Smith, Holly; Biggs, Juliet; Hodge, Michael

doi:10.3389/fbuil.2016.00030

Cited by 21 publications

(29 citation statements)

References 24 publications

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“…In the absence of more detailed official data, WorldPop can be considered the best freeware option. For developing countries, WorldPop is preferable to other available resources (Goda et al, 2016) such as LandScan (Dobson et al, 2000) or GPW4 (CIESIN, 2016). Fig.…”

Section: Populationmentioning

confidence: 99%

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Seismic hazard and risk in Bhutan

et al. 2020

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We present the first modern seismic hazard and risk assessment in the Bhutan Himalaya. We used a fault-based probabilistic seismic hazard analysis based on fault locations, slip-rates and paleoseismic earthquake data. We worked with two seismic intensity measures: the peak-ground acceleration (PGA) and Modified Mercalli Intensity (MMI). We extend the hazard analysis to risk by using local building distribution data and making various assumptions about building distribution and fragility. We find, unsurprisingly, that the Main Himalayan Thrust (MHT) is the primary source of hazard, with oblique strike-slip faults cutting across and beneath the Himalaya, and extensional grabens on the northern edge of Bhutan a secondary hazard. The hazard is highest in the southern part of Bhutan where the MHT is shallow, and site conditions lead to amplification of shaking. The risk does not reflect the hazard solely, but also the distribution of exposure, which is concentrated in the cities. We also simulated the 1714 MW8 earthquake, producing 10,000 possible shakemaps in terms of PGA and MMI; we find that many locations could experience PGA values of over 1 g, and on average, up to 18% of the Bhutanese population could be affected. Refining the probable frequency of larger events on the MHT in this region, developing local Ground Motion Prediction Equations, creating tailored vulnerability models for typical Bhutanese buildings, and improving the exposure mapping would most improve the hazard and risk results shown here. The existing building code of Bhutan, adopted from the Indian Seismic Zonation of 2002 (BIS-1893, 2002), uses a PGA of 0.36 g uniformly applied across the entire country. Our study, however, presents a non-uniform hazard level across the country and thus questions the relevancy of the current code of construction practices in the country.

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Section: Populationmentioning

confidence: 99%

“…for W5, 20.81 for C1, 5 for A1 and 7.30 for RM3. As suggested by Goda et al (2016), to map the population data to building data, the number of people is divided by the average occupancy. Both the average and specific density occupancy for the different typologies are used in the following.…”

Section: Buildingsmentioning

confidence: 99%

Seismic hazard and risk in Bhutan

et al. 2020

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“…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).…”

Section: ;mentioning

confidence: 99%

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

Williams¹,

Mdala²,

Fagereng³

et al. 2020

Preprint

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Abstract. Seismic hazard is frequently characterised using instrumental seismic records. However, in regions where the instrumental record is short relative to earthquake repeat times, extrapolating it to estimate seismic hazard can misrepresent the probable location, magnitude, and frequency of future large earthquakes. Although paleoseismology can address this challenge, this approach requires certain geomorphic settings and carries large inherent uncertainties. Here, we outline how fault slip rates and recurrence intervals can be estimated through an approach that combines fault geometry, earthquake-scaling relationships, geodetically derived regional strain rates, and geological constraints of regional strain distribution. We then apply this approach to the southern Malawi Rift where, although no on-fault slip rate measurements exist, there are theoretical and observational constraints on how strain is distributed between border and intrabasinal faults. This has led to the development of the South Malawi Active Fault Database (SMAFD), the first database of its kind in the East African Rift System (EARS) and designed so that the outputs can be easily incorporated into Probabilistic Seismic Hazard Analysis. We estimate earthquake magnitudes of MW 5.4–7.2 for individual fault sections in the SMAFD, and MW 6.0–7.8 for whole fault ruptures. These potentially high magnitudes for continental normal faults reflect southern Malawi's 11–140 km long faults and thick (30–35 km) seismogenic crust. However, low slip rates (intermediate estimates 0.05–0.8 mm/yr) imply long recurrence intervals between events: 102–105 years for border faults and 103–106 years for intrabasinal faults. Sensitivity analysis indicates that the large range of these estimates can be reduced most significantly from an improved understanding of the rate and partitioning of rift-extension in southern Malawi, earthquake scaling relationships, and earthquake rupture scenarios. Hence these are critical areas for future research. The SMAFD provides a framework for using geological and geodetic information to characterize seismic hazard in low strain rate settings with few on-fault slip rate measurements, and could be adapted for use elsewhere in the EARS or globally.

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“…5, local characteristics of the current building stock in Central and Southern Malawi are investigated based on a building survey, which was conducted by the authors between 10th and 20th July 2017. The survey areas are susceptible to seismic hazard based on the tectonics around the southern part of Lake Malawi (Hodge et al 2015;Chapola and Gondwe 2016;Goda et al 2016). Important results of this work are that discrepancies between building stock information derived from global databases (e.g.…”

Section: International Federation Of Red Cross 2011)mentioning

confidence: 99%

“…the PAGER-based global building classification and the 2017-survey-based local building classification. Only brief descriptions of the seismic risk analysis method are provided in this paper; more detailed information can be found in Goda et al (2016Goda et al ( , 2018.…”

Section: Effects Of Building Classifications On Seismic Risk Assessmentmentioning

confidence: 99%

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

Kloukinas

Novelli

Kafodya

et al. 2019

J Hous and the Built Environ

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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.

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Seismic Risk Assessment of Urban and Rural Settlements around Lake Malawi

Cited by 21 publications

References 24 publications

Seismic hazard and risk in Bhutan

Seismic hazard and risk in Bhutan

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

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

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