Abstract. Seismic hazard is commonly characterised using instrumental seismic records.
However, these records are short relative to earthquake repeat times, and
extrapolating 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 setting, is resource intensive, and can carry large inherent
uncertainties. Here, we outline how fault slip rates and recurrence
intervals can be estimated by combining fault geometry, earthquake-scaling
relationships, geodetically derived regional strain rates, and geological
constraints of regional strain distribution. We apply this approach to
southern Malawi, near the southern end of the East African Rift, and where,
although no on-fault slip rate measurements exist, there are constraints on
strain partitioning between border and intra-basin faults. This has led to
the development of the South Malawi Active Fault Database (SMAFD), a
geographical database of 23 active fault traces, and the South Malawi
Seismogenic Source Database (SMSSD), in which we apply our systems-based
approach to estimate earthquake magnitudes and recurrence intervals for the
faults compiled in the SMAFD. We estimate earthquake magnitudes of MW 5.4–7.2 for individual fault sections in the SMSSD and MW 5.6–7.8 for
whole-fault ruptures. However, low fault 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 intra-basin faults. Sensitivity analysis indicates that the large
range of these estimates can best be reduced with improved geodetic
constraints in southern Malawi. The SMAFD and SMSSD provide a framework for
using geological and geodetic information to characterise seismic hazard in
regions with few on-fault slip rate measurements, and they could be adapted for
use elsewhere in the East African Rift and globally.
Strain and Velocity Across the Great Basin Derived From 15‐ka Fault Slip Rates: Implications for Continuous Deformation and Seismic Hazard in the Walker Lane, California‐Nevada, USA
