Fault-based probabilistic seismic hazard analysis in regions with low strain rates and a thick seismogenic layer: a case study from Malawi

SUMMARY Historical and instrumental earthquake catalogs in low strain rate regions are not necessarily indicative of the long-term spatio-temporal distribution seismicity. This implies that probabilistic seismic hazard analysis (PSHA) should also consider geologic geodetic data through fault-based seismogenic sources. However, it is always clear how on-fault magnitude-frequency distributions (MFDs) be described and, if layer especially thick, fault sources extrapolated down-dip. We explore these issues context a new PSHA for Malawi, where regional extensional rates 0.5–2 mm yr−1, 30–40-km catalog ∼60 yr long were recently collated Malawi Seismogenic Source Model. Furthermore, one several countries along East African Rift exposure to growing, but does typically use stochastic event different source down-dip extents MFDs. Our indicates levels highest Gutenberg–Richter MFD, even at probabilities exceedance (2 per cent 50 yr), whilst sensitive relatively short (<50 km) For sites close (<40 km), doubled compared previous instrumental-seismicity based Malawi. Cumulatively, results highlight need careful modelling elsewhere Africa Rift.