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SUMMARY:Reaching for the Holy Grail of Modern Global Seismology: New insig
 hts into the centre of the Earth from the detection of J waves - Prof. Hrv
 oje Tkalčić
DTSTART:20180625T150000Z
DTEND:20180625T160000Z
UID:TALK106540@talks.cam.ac.uk
CONTACT:Sanne Cottaar
DESCRIPTION:More than 75 years ago\, the Earth's core was hypothesized to 
 be solid in the centre as a result of a liquid–solid phase change in iro
 n\, which implies that shear waves in its solid part (seismic J–phase) s
 hould exist. Some claims of such observations have been made\, but the J
 –phase has remained elusive until the present day. According to some res
 earchers\, the compressional body waves that convert to shear waves during
  passage through the inner core (a.k.a. PKJKP) were termed "the holy grail
  of body wave seismology".\n\nI will tell a story on how the quest for the
  PKJKP took an unexpected turn: we employed recent advances in the global 
 correlation wavefield to detect the presence of the J waves unequivocally.
 \n\nFrom the observations of the J–phase\, we obtained new estimates for
  shear properties of the Earth's centre\, including shear wave speed\, res
 istance to shear and attenuation.\n\nI will present evidence for a "soft i
 nner core"\, which explains the absence of PKJKP waves in the seismic wave
 field and has significant implications for geodynamics and mineral physics
  studies.\n
LOCATION:Marine/Wolfson Building lecture hall\, Bullard Labs.
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