标题：A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: active fault and seismogenic source databases for southern Malawi
摘要：Seismic hazard is commonly characterised using instrumental seismic records.However, these records are short relative to earthquake repeat times, andextrapolating to estimate seismic hazard can misrepresent the probablelocation, magnitude, and frequency of future large earthquakes. Althoughpaleoseismology can address this challenge, this approach requires certaingeomorphic setting, is resource intensive, and can carry large inherentuncertainties. Here, we outline how fault slip rates and recurrenceintervals can be estimated by combining fault geometry, earthquake-scalingrelationships, geodetically derived regional strain rates, and geologicalconstraints of regional strain distribution. We apply this approach tosouthern Malawi, near the southern end of the East African Rift, and where,although no on-fault slip rate measurements exist, there are constraints onstrain partitioning between border and intra-basin faults. This has led tothe development of the South Malawi Active Fault Database (SMAFD), ageographical database of 23 active fault traces, and the South MalawiSeismogenic Source Database (SMSSD), in which we apply our systems-basedapproach to estimate earthquake magnitudes and recurrence intervals for thefaults 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 forwhole-fault ruptures. However, low fault slip rates (intermediate estimates∼ 0.05–0.8 mm/yr) imply long recurrence intervals betweenevents: 102–105 years for border faults and 103–106 years for intra-basin faults. Sensitivity analysis indicates that the largerange of these estimates can best be reduced with improved geodeticconstraints in southern Malawi. The SMAFD and SMSSD provide a framework forusing geological and geodetic information to characterise seismic hazard inregions with few on-fault slip rate measurements, and they could be adapted foruse elsewhere in the East African Rift and globally.
