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CATEGORIES:Bullard Laboratories Wednesday Seminars
SUMMARY:Towards a new global earthquake catalogue - Full w
 aveform constraints on earthquake mechanisms and t
 heir uncertainty - Tom Garth - University of Oxfor
 d and ISC
DTSTART;TZID=Europe/London:20191127T160000
DTEND;TZID=Europe/London:20191127T170000
UID:TALK131305AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/131305
DESCRIPTION:For any given moderate magnitude (5.8 – 7.0 Mw) ea
 rthquake there are multiple constraints on the ear
 thquake source parameters provided by various glob
 al and regional earthquake monitoring agencies. Wh
 ile the broad characteristics of the location and 
 mechanisms are often in agreement\, there is still
  a large range of depths\, focal mechanisms and ev
 en epicentres reported for the same earthquake. In
  this talk I will outline a new procedure develope
 d in collaboration between Oxford seismology group
  and the International Seismological Centre (ISC) 
 to constrain the moment tensor\, source time funct
 ion and depths of moderate magnitude earthquakes\,
  along with the uncertainty in these source parame
 ters.\n\nWe use a Bayesian inversion scheme to pro
 vide an ensemble of point source earthquake models
  that give an indication of the potential variabil
 ity of the earthquake mechanism and depth. We show
  that by jointly inverting for the earthquake sour
 ce time function\, moment tensor and depth we can 
 improved resolution to the earthquake depth\, as w
 ell as a measure of the uncertainty in the earthqu
 ake mechanism\, source time function and depth. Th
 e increased depth resolution that is seen particul
 arly for shallow events is achieved by accounting 
 for the surface reflected depth phases. For interm
 ediate depth earthquakes (70 - 300 km depth) it is
  well understood that these phases are strongly de
 pth dependent\, but for shallow events they are of
 ten subsumed within the source time function\, and
  are therefore unobservable. By jointly solving fo
 r the earthquake depth and the source time functio
 n\, we are able to assess the likelihood of a shal
 low earthquake occurring at a range of depths.\n\n
 We hope that this method will offer a new ISC prod
 uct\, in the form of source time functions for mod
 erate magnitude earthquakes\, as well as improving
  the depth determination for shallow earthquakes i
 n remote and un-instrumented parts of the world.
LOCATION:Marine/Wolfson Building lecture hall\, Bullard Lab
 s.
CONTACT:Alistair Boyce
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