Preprints
https://doi.org/10.5194/egusphere-2022-304
https://doi.org/10.5194/egusphere-2022-304
 
17 Jun 2022
17 Jun 2022
Status: this preprint is open for discussion.

The Luangwa Rift Active Fault Database and fault reactivation along the southwestern branch of the East African Rift

Luke N. J. Wedmore1, Tess Turner1, Juliet Biggs1, Jack N. Williams1,2,3, Henry M. Sichingabula4, Christine Kabumbu4, and Kawawa Banda5 Luke N. J. Wedmore et al.
  • 1School of Earth Sciences, University of Bristol, Bristol, UK
  • 2School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK
  • 3Department of Geology, University of Otago, Dunedin, New Zealand
  • 4Department of Geography and Environmental Studies, University of Zambia, Lusaka, Zambia
  • 5Department of Geology, School of Mines, University of Zambia, Lusaka, Zambia

Abstract. Seismic hazard assessment in slow straining regions is challenging because earthquake catalogues only record events from approximately the last 100 years, whereas earthquake recurrence times on individual faults can exceed 1,000 years. Systematic mapping of active faults allows fault sources to be used within probabilistic seismic hazard assessment, which overcomes the problems of short-term earthquake records. We use Shuttle Radar Topography Mission (SRTM) data to analyse surface deformation in the Luangwa Rift in Zambia and develop the Luangwa Rift Active Fault Database (LRAFD). The LRAFD is an open-source geospatial database containing active fault traces and their attributes and is freely available at: https://doi.org/10.5281/zenodo.6513691. We identified 18 faults that display evidence for Quaternary activity and empirical relationships suggest that these faults could cause earthquakes up to Mw 8.1, which would exceed the magnitude of historically recorded events in southern Africa. On the four most prominent faults, the median height of Late Quaternary fault scarps varies between 12.9 ± 0.4 and 19.2 ± 0.9 m, which suggests they were formed by multiple earthquakes. Deformation is focused on the edges of the Luangwa Rift: the most prominent Late Quaternary fault scarps occur along the 207 km long Chipola and 142 km long Molaza faults, which are the rift border faults and the longest faults in the region. We associate the scarp on the Molaza Fault with possible surface ruptures from two 20th Century earthquakes. Thus, the LRAFD reveals new insights into active faulting in southern Africa and presents a framework for evaluating future seismic hazard.

Luke N. J. Wedmore et al.

Status: open (until 30 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-304', Junjie Ren, 01 Jul 2022 reply

Luke N. J. Wedmore et al.

Data sets

Luangwa Rift Fault Scarp Measurements Turner, T., Wedmore, L. N. J., Biggs, J. https://doi.org/10.5281/zenodo.6513545

Luangwa Rift Active Fault Database Wedmore, L. N. J., Turner, T., Biggs, J., Williams, J. N., Sichingabula, H., Kabumbu, C., Banda, K. https://doi.org/10.5281/zenodo.6513691

Luangwa Rift Seismogenic Source Properties Turner, T., Wedmore, L. N. J., Biggs, J., Williams, J. N., Sichingabula, H., Kabumbu, C., Banda, K. https://doi.org/10.5281/zenodo.6513778

Luke N. J. Wedmore et al.

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Short summary
Mapping and compiling the attributes of faults capable of hosting earthquakes is important for the next generation of seismic hazard assessment. We document 18 active faults in the Luangwa Rift, Zambia in an active fault database. These faults are between 9 and 207 km long, offset Quaternary sediments, have scarps up to ~30 m high and are capable of causing earthquakes between Mw5.8 and 8.1. We correlate the Molaza fault with surface ruptures from two unatributted M6+ 20th century earthquakes.