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SUMMARY:Towards a new global earthquake catalogue - Full waveform constrai
 nts on earthquake mechanisms and their uncertainty - Tom Garth - Universit
 y of Oxford and ISC
DTSTART:20191127T160000Z
DTEND:20191127T170000Z
UID:TALK131305@talks.cam.ac.uk
CONTACT:Alistair Boyce
DESCRIPTION:For any given moderate magnitude (5.8 – 7.0 Mw) earthquake t
 here are multiple constraints on the earthquake source parameters provided
  by various global and regional earthquake monitoring agencies. While the 
 broad characteristics of the location and mechanisms are often in agreemen
 t\, there is still a large range of depths\, focal mechanisms and even epi
 centres reported for the same earthquake. In this talk I will outline a ne
 w procedure developed in collaboration between Oxford seismology group and
  the International Seismological Centre (ISC) to constrain the moment tens
 or\, source time function and depths of moderate magnitude earthquakes\, a
 long with the uncertainty in these source parameters.\n\nWe use a Bayesian
  inversion scheme to provide an ensemble of point source earthquake models
  that give an indication of the potential variability of the earthquake me
 chanism and depth. We show that by jointly inverting for the earthquake so
 urce time function\, moment tensor and depth we can improved resolution to
  the earthquake depth\, as well as a measure of the uncertainty in the ear
 thquake mechanism\, source time function and depth. The increased depth re
 solution that is seen particularly for shallow events is achieved by accou
 nting for the surface reflected depth phases. For intermediate depth earth
 quakes (70 - 300 km depth) it is well understood that these phases are str
 ongly depth dependent\, but for shallow events they are often subsumed wit
 hin the source time function\, and are therefore unobservable. By jointly 
 solving for the earthquake depth and the source time function\, we are abl
 e to assess the likelihood of a shallow earthquake occurring at a range of
  depths.\n\nWe hope that this method will offer a new ISC product\, in the
  form of source time functions for moderate magnitude earthquakes\, as wel
 l as improving the depth determination for shallow earthquakes in remote a
 nd un-instrumented parts of the world.
LOCATION:Marine/Wolfson Building lecture hall\, Bullard Labs.
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