The Malawi Active Fault Database: an onshore-offshore database for
regional assessment of seismic hazard and tectonic evolution
Abstract
We present the Malawi Active Fault Database (MAFD), a geospatial
database of 114 active fault traces in Malawi, and in neighboring
Tanzania and Mozambique. The MAFD has been developed from a
multidisciplinary dataset: high resolution digital elevation models,
field observations, aeromagnetic and gravity data, and seismic
reflection surveys from offshore Lake Malawi. Active faults longer than
50 km are found throughout Malawi, where seismic risk is increasing due
to its rapidly growing population and its seismically vulnerable
building stock. The MAFD also provides an opportunity to investigate the
population of normal faults in an incipient continental rift. We find
that the null hypothesis that the distribution of fault lengths in the
MAFD is described by a power law cannot be rejected. Furthermore, a
power-law distribution of faults in Malawi is consistent with its thick
seismogenic crust (~35 km), and low (<8%)
regional extensional strain that is predominantly (50-75%) accommodated
across relatively long hard-linked border faults. Cumulatively, the data
and inferences drawn from the MAFD highlight the importance of
integrating onshore and offshore geological and geophysical data to
develop active fault databases along the East African Rift and similar
continental settings, both to understand the regional seismic hazard and
tectonic evolution.