26 September 2012 – Seminar
When: 11am on Wednesday, 26 September 2012
Where: DIAS, Geophysics Section, 5 Merrion Square, Dublin 2, (library)
Speaker: Dr. Marianne Karplus
Title: Crustal structure and tectonics of north Tibet from controlled-source and broadband seismology
Abstract:
I will present on the three-dimensional crustal structure and plateau growth in the north Tibetan Plateau from the Qiangtang terrane to the Qaidam Basin. The INDEPTH IV project seismology group recently collected an abundance of data in north Tibet, and we use those active- and passive-source seismic datasets to investigate how north Tibet is deforming in response to the India-Asia collision including whether there may be mid-or lower-crustal flow within the plateau.
Our wide-angle reflection and refraction velocity model shows that the central Qaidam Basin resembles average continental crust, whereas the Songpan-Ganzi terrane and East Kunlun Mountains exhibit thickened, lower-velocity crust also characteristic of southern Tibet. Combining those results with P-wave receiver functions, we relocate the 20-km crustal thickness change to ~45 km north of the Kunlun Mountains topographic front, in a region of overlapping bright Moho reflectors at ~70 km and ~50 km. The crustal thickness change is unrelated to the strike-slip North Kunlun Fault. Crustal velocities and impedance contrasts suggest that weak Tibetan lower crust is injected northward beneath stronger Qaidam crust without southward subduction of Eurasian lithosphere.
Finally, at the broadest scale, we use ambient noise tomography to map regional differences in crustal Rayleigh wave group velocities across a larger area of north Tibet including the Qiangtang terrane. For periods of 8-24 s (sampling from ~10-35 km depth within the crust), we observe striking velocity changes at the major east-west Bangong-Nujiang and Jinsha suture zones as well as the Kunlun-Qaidam boundary in the mid- to upper-crust. Our data also supports the hypothesis that north Tibet (~ 32°-36° N) is underlain by a low velocity zone at ~20-30 km depth.
Leave a Comment
Last Updated: 22nd March 2016 by Anna
2012-09-26 – Seminar: Dr. Marianne Karplus
26 September 2012 – Seminar
When: 11am on Wednesday, 26 September 2012
Where: DIAS, Geophysics Section, 5 Merrion Square, Dublin 2, (library)
Speaker: Dr. Marianne Karplus
Title: Crustal structure and tectonics of north Tibet from controlled-source and broadband seismology
Abstract:
I will present on the three-dimensional crustal structure and plateau growth in the north Tibetan Plateau from the Qiangtang terrane to the Qaidam Basin. The INDEPTH IV project seismology group recently collected an abundance of data in north Tibet, and we use those active- and passive-source seismic datasets to investigate how north Tibet is deforming in response to the India-Asia collision including whether there may be mid-or lower-crustal flow within the plateau.
Our wide-angle reflection and refraction velocity model shows that the central Qaidam Basin resembles average continental crust, whereas the Songpan-Ganzi terrane and East Kunlun Mountains exhibit thickened, lower-velocity crust also characteristic of southern Tibet. Combining those results with P-wave receiver functions, we relocate the 20-km crustal thickness change to ~45 km north of the Kunlun Mountains topographic front, in a region of overlapping bright Moho reflectors at ~70 km and ~50 km. The crustal thickness change is unrelated to the strike-slip North Kunlun Fault. Crustal velocities and impedance contrasts suggest that weak Tibetan lower crust is injected northward beneath stronger Qaidam crust without southward subduction of Eurasian lithosphere.
Finally, at the broadest scale, we use ambient noise tomography to map regional differences in crustal Rayleigh wave group velocities across a larger area of north Tibet including the Qiangtang terrane. For periods of 8-24 s (sampling from ~10-35 km depth within the crust), we observe striking velocity changes at the major east-west Bangong-Nujiang and Jinsha suture zones as well as the Kunlun-Qaidam boundary in the mid- to upper-crust. Our data also supports the hypothesis that north Tibet (~ 32°-36° N) is underlain by a low velocity zone at ~20-30 km depth.
Category: Geophysics Section News & Events
Big thank you to @MartinaPQuinn of @helloalicepr for moderating the discussion, and of course to our panel @NeasaMcG @CormacORafferty and @laoneill111
@CormacORafferty "to cut yourself off from fundamental research means you could miss out on some of the biggest ideas"
@laoneill "it's our job as researchers to keep reminding governments how important basic research is" "For Dev basic research being carried out in Ireland was a badge of pride"
@NeasaMcG Schrödinger's work in causality was not well received by the religious authorities at the time At the same time DIAS did have Catholic priests working on research projects in the early days, so there was not the conflict you might think between science and religion
@laoneill111 Schrödinger was very popular in social circles in Dublin, a bit of a renaissance man
@CormacORafferty Schrödinger was gifted at explaining difficult concepts
@CormacORafferty on how unsuccessful work, in Schrödinger's case, unified field theory, is just as important part of science. And no one has managed to crack it yet! And not forgetting the cat
@laoneill111 how Schrödinger's book inspired scientists to change fields and result in the finding of the double helix.
@NeasaMcG explaining how DIAS came about and how Schrödinger was attracted to Ireland #DIASdiscovers
Panel Discussion getting underway! @laoneill111 @CormacORafferty @NeasaMcG @MartinaPQuinn
We're half way through the documentary... Join us for the rest and the fascinating discussion to follow DM for link
@Stella15882 @NeasaMcG @HistFest @lukeoneil47 @CormacORafferty @MartinaPQuinn Stella, send me an email. I'll get a link to you communications@dias.ie
Starting in just over an hour we have limited tickets left for tonights broadcast and panel discussion. Get your free ticket now twitter.com/DIAS_Dublin/st…
Culture Night 2020 Booking Links! - Virtual Tour of DIAS Dunsink Observatory: eventbrite.ie/e/118043576515 - Earthquakes and other Geohazards: eventbrite.ie/e/earthquakes-… - Taifeadaí Cartlainne ó Scoil an Léinn Cheiltigh: eventbrite.ie/e/taifeadai-ca… Join us from 5pm! #CultureNight2020
@dias_geophysics have developed something special for @galway2020 in collaboration with composer David Stalling. It is an audio-visual composition “Palace of Ships,” based on sounds, images and seismic data from DIAS’ @SEA_SEIS Expeditions. More: dias.ie/2020/09/14/dia…
Meet some of our panelists for tomorrows discussion on the impact and legacy of the work carried out by Erwin Schroedinger during his time in Ireland as our first Director of Theoretical Physics Grab a free ticket here: eventbrite.ie/e/115984908985