09. April 2020 - 19:30 till 21:30
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What can structural geology tell us about seismic hazard in the East African Rift System? | Department of Earth Sciences | Thursday, 09. April 2020

Dr Jack Williams (university of Cardiff) will give this Oxford Geology Group Wager Lecture.
The largest instrumentally recorded earthquake in the East African Rift System (EARS) was the 1910 M 7.4 Rukwa earthquake in southern Tanzania. However, although this instrumental record is the main input into current seismic hazard models for the EARS, this record is likely incomplete and does fully not capture the activity of EARS faults, which may only rupture once every 10,000 years. In this talk, I will discuss some of the geomorphic and geologic evidence for M 7-8 earthquakes in southern Malawi, and how this can be used to reassess the rift’s seismic hazard. I will also explore how normal faults in Malawi rapidly achieve length  >100 km as they exploit Proterozoic crustal-scale weaknesses. In this way, they are likely to rupture in rare large (M>7) earthquakes as opposed to more frequent moderate sized (M~6) events. If true, then it indicates that the Malawi Rift’s current seismic hazard has been preconditioned by pre-existing Proterozoic fabrics.