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SUMMARY:Earthquake scaling laws and the nucleation process - Stefan Nielse
 n (Durham University)
DTSTART:20251203T140000Z
DTEND:20251203T150000Z
UID:TALK239392@talks.cam.ac.uk
CONTACT:Adriano Gualandi
DESCRIPTION:Geodetic observations of megathrust events at plate boundaries
  (e.g. Chile\, Japan) show weeks- to months-long slow-slip preceding some 
 great earthquakes. Comparable long precursory phases are generally absent 
 for smaller intraplate events. Does a long nucleation somehow forecast a l
 arge magnitude earthquake? Scaling laws tell us that earthquakes should be
  self-similar at all scales\, yet\, systematic differences emerge in how t
 hey nucleate\, accelerate\, and arrest. Motivated by contrasting observati
 onal results and a long-standing debate\, I first review evidence from nat
 ural earthquakes\, laboratory experiments and conflicting views on whether
  the initial growth of moment rate is scale-invariant across magnitudes or
 \, instead\, shows longer characteristic rise times for larger earthquakes
 .\nTo interpret these observations\, I revisit Griffith’s critical crack
  and explore a simple analytical solution for rupture acceleration based o
 n the energy balance. This solution predicts a universal\, self-similar br
 eakout phase in which rupture velocity and acceleration scale with the ini
 tial nucleation size. I test and extend this result using 2D and 3D dynami
 c rupture simulations\, including heterogeneous stress and complex nucleat
 ion geometries\, and show that the scaling persists when expressed in term
 s of a characteristic length and a geometrically averaged limiting velocit
 y. Laboratory photoelastic experiments on transparent materials further su
 pport the predicted scaling between nucleation size and acceleration.\nFin
 ally\, I explore how fault segmentation and self-affine stress heterogenei
 ty may couple nucleation size to overall fault dimension\, and discuss imp
 lications for probabilistic forecasting and earthquake early warning\, par
 ticularly whether early moment-rate growth may encode information about ev
 entual event size.
LOCATION:Wolfson Lecture Theatre
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