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SUMMARY:Fault orientation in earthquake seismic precursors: Insights from 
 the laboratory - Carolina Giorgetti\, ENS Paris
DTSTART:20250319T140000Z
DTEND:20250319T150000Z
UID:TALK228682@talks.cam.ac.uk
CONTACT:Adriano Gualandi
DESCRIPTION:Faults in the brittle crust lie at any orientation to the far-
 field stress. However\, laboratory experiments designed to investigate ear
 thquake physics commonly simulate favorably oriented faults\, potentially 
 overlooking the complexity of natural fault behavior. Here\, we assess the
  role of stress field orientation in fault reactivation and earthquake pre
 cursors by conducting triaxial sawcut experiments with laboratory faults o
 riented at different angles to the maximum principal stress\, ranging from
  30° to 70°. The samples were instrumented with strain gauges and piezoe
 lectric sensors. Laboratory well-oriented faults describe a rather simple 
 system in which the elastic energy is stored via the deformation of the su
 rrounding host rock during the inter-seismic period and released via on-fa
 ult slip during the co-seismic phase with associated precursor acoustic ac
 tivity. Consistent with previous laboratory data\, an abrupt increase in t
 he on-fault acoustic emission rate occurs shortly before the laboratory ea
 rthquake. A more complex picture emerges when deforming laboratory misorie
 nted faults. Particularly\, acoustic emissions and strain gauge data indic
 ate that when the fault is misoriented\, off-fault permanent deformation o
 ccurs well before fault reactivation. The stress state in the host rock su
 rrounding the fault is indeed far beyond the one required for the onset of
  inelastic deformation. In this case\, acoustic activity distributed in th
 e rock volume during the pre-seismic phase is associated with permanent de
 formation in the critically stressed host rock and is not a direct precurs
 or to the following laboratory earthquake. Unlike well-oriented faults\, l
 aboratory misoriented faults lack detectable seismic precursors. The labor
 atory-observed increase in acoustic activity prior to\, but not precursor 
 of\, misoriented fault reactivation impacts our understanding of earthquak
 e precursors in natural faults.
LOCATION:Wolfson Lecture Theatre
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