The School of Geography, Earth and Environmental Sciences organises a regular series of research seminars throughout the academic year to which everyone is welcome to attend. Speakers - both external and internal to the University - will talk on topics related to all aspects of Earth Sciences.
Today's speaker is Dr Lucy Campbell, Post-doctoral Research Fellow in Structural Geology and Rock Deformation, from the School of Geography, Earth and Environmental Sciences.
The geological record of seismicity proves invaluable for ground-truthing models of deformation and rheology used to understand earthquake behaviour throughout all levels of the earth’s crust. Recognising where ancient earthquakes occurred in exhumed fault zones is assisted by the presence of the fault rocks such as pseudotachylyte, generated as a melt along fault planes due to frictional heating during seismic slip. Rapid cooling of pseudotachylytes lock in a useful snapshot of information about conditions during the earthquake, and they can be used to estimate seismic parameters such as stress drop and magnitude.
When pseudotachylytes are found in otherwise ductile mylonites more typical of lower crustal conditions, this raises interesting questions – can earthquakes nucleate below the seismogenic zone of the shallow crust, and how are the conditions necessary for brittle slip generated so transiently?
In the Lofoten Islands, northern Norway, a field site preserving lower crustal fault zones acts as a 'natural laboratory' to help us investigate such problems.