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SUMMARY:The origin of stress- and fluid-driven seismicity in volcanic sett
 ings: a laboratory perspective - Dr Philip Benson\, University of Portsmou
 th
DTSTART:20220210T150000Z
DTEND:20220210T160000Z
UID:TALK167252@talks.cam.ac.uk
CONTACT:David Wallis
DESCRIPTION:Seismicity has long been used to monitor volcanoes and active 
 volcanic areas. In these regions\, rising magma stresses the overlying roc
 k to open (or reopen) conduits for fluid and gas flow. The fracturing and 
 ensuing fluid-flow generates a range of seismicity frequently characterise
 d by their spectral properties. These include Volcano-Tectonic (VT) events
  generated by rock fracture\, Long Period (LP) seismicity generally interp
 reted as indicators of fluid migration\, and Hybrid events characterized b
 y a high frequency (VT-like) onset and low frequency (LP-like) coda. In ma
 ny cases these data are reliable precursors to eruptions after extended re
 pose (volcanoes that have been quiet for 100 years or more)\, and are freq
 uently detected weeks or months before an eruption. For some years the det
 ection of LP events was heralded as a new and more accurate forecasting (w
 arning) method directly linked to fluid movement\; however\, this has prov
 en inconclusive. To decipher these signals\, and better constrain their ph
 ysical generation mechanisms\, laboratory rock physics experiments simulat
 ing these different seismic sequences have been developed. Here\, I presen
 t data from triaxial rock deformation experiments collected over ~15 years
  and from a range of rock types and pressure/temperature conditions. Colle
 ctively\, they suggest that Hybrid events are more likely to be generated 
 when fluid is present\, and that LP events are enhanced by elevated temper
 ature conditions due to localized fluid phase change. However\, recently p
 ublished work has now also shown that a common low-cohesion volcanic sedim
 ent from Campi Flegrei caldera (Italy) produces Long Period and low freque
 ncy seismicity whilst undergoing deformation in dry conditions rather than
  solely fluid-saturated conditions\, with implications for interpreting up
 per edifice stability and hazard from seismic sequences.
LOCATION:Department of Earth Sciences\, Tilley Lecture Theatre
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