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IRIS WEBINAR - Seismology at the Roof of the World - THIS WEDNESDAY
From: Andy Frassetto <andyf@xxxxxxxx>IRIS WEBINAR - Seismology at the Roof of the World - THIS WEDNESDAY
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"Crustal Structure and Tectonics of
Northeast Tibet from INDEPTH IV Wide-Angle Refraction and
Receiver Functions" will be presented at 1 pm EDT (5 pm UTC) on
Wednesday, 5/21.
Please register if you intend to participate in the webinar live: https://www2.gotomeeting.com/register/874190338
You will be emailed a confirmation containing a link for watching the live broadcast. Afterwards, IRIS will post the webinar here: http://www.youtube.com/user/IRISEnO. Access to older webinars and related materials and information are found at the webinar page (http://www.iris.edu/hq/webinar/), which is soon to be updated.
Presenters: Dr. Marianne Karplus (Post-doc, University of Southhampton, United Kingdom)
Abstract: The project INDEPTH (International Deep Profiling of Tibet and the Himalaya), phase IV, seismology group collected an abundance of active- and passive-source seismic data in north Tibet from 2007-2009, and I will present results from those investigations and implications for crustal structure and tectonics. Specifically, we derived seismic structure and P-wave velocities from the 270-km long, roughly north-south, active-source, wide-angle reflection and refraction profile crossing the Songpan-Ganzi terrane, Kunlun Mountains, and Qaidam Basin using first arrivals tomography and ray tracing. Then we calculated P-to-S receiver functions using linear and regional arrays of passive seismic stations in the same areas to provide independent constraints on crustal thickness, lithospheric structure, and Vp/Vs ratios.
The wide-angle reflection and refraction velocity model shows a crustal thickness change from 70 km beneath the Kunlun Mountains to 50 km beneath central Qaidam. Crustal P-wave velocities in the thickened Songpan-Ganzi terrane and Kunlun Mountains exhibit lower velocity crust also characteristic of southern Tibet, whereas crustal velocities in the central Qaidam Basin resemble average continental crust. In contrast to previous work, we relocate the 20-km crustal thickness change to ~40 km north of the Kunlun Mountains topographic front, in a region of overlapping bright Moho reflectors at ~70 km and ~50 km. P-receiver functions calculated for passive seismic stations coincident with the active-source profile show a very similar Moho structure. P-receiver functions calculated for stations scattered along-strike from 91.5° to 98°E near the Kunlun-Qaidam boundary show that the width of the overlapping region ranges from ~10-40 km at different locations along the boundary, and near Golmud the deeper reflector may dip northwards. The crustal thickness change appears unrelated to the strike-slip North Kunlun Fault. At depths shallower than 100 km, we also see no evidence of southward subduction of Eurasian lithosphere. Crustal velocities and impedance contrasts suggest that instead weak Tibetan lower crust is injected northward beneath stronger Qaidam crust.
System Requirements Please register if you intend to participate in the webinar live: https://www2.gotomeeting.com/register/874190338
You will be emailed a confirmation containing a link for watching the live broadcast. Afterwards, IRIS will post the webinar here: http://www.youtube.com/user/IRISEnO. Access to older webinars and related materials and information are found at the webinar page (http://www.iris.edu/hq/webinar/), which is soon to be updated.
Presenters: Dr. Marianne Karplus (Post-doc, University of Southhampton, United Kingdom)
Abstract: The project INDEPTH (International Deep Profiling of Tibet and the Himalaya), phase IV, seismology group collected an abundance of active- and passive-source seismic data in north Tibet from 2007-2009, and I will present results from those investigations and implications for crustal structure and tectonics. Specifically, we derived seismic structure and P-wave velocities from the 270-km long, roughly north-south, active-source, wide-angle reflection and refraction profile crossing the Songpan-Ganzi terrane, Kunlun Mountains, and Qaidam Basin using first arrivals tomography and ray tracing. Then we calculated P-to-S receiver functions using linear and regional arrays of passive seismic stations in the same areas to provide independent constraints on crustal thickness, lithospheric structure, and Vp/Vs ratios.
The wide-angle reflection and refraction velocity model shows a crustal thickness change from 70 km beneath the Kunlun Mountains to 50 km beneath central Qaidam. Crustal P-wave velocities in the thickened Songpan-Ganzi terrane and Kunlun Mountains exhibit lower velocity crust also characteristic of southern Tibet, whereas crustal velocities in the central Qaidam Basin resemble average continental crust. In contrast to previous work, we relocate the 20-km crustal thickness change to ~40 km north of the Kunlun Mountains topographic front, in a region of overlapping bright Moho reflectors at ~70 km and ~50 km. P-receiver functions calculated for passive seismic stations coincident with the active-source profile show a very similar Moho structure. P-receiver functions calculated for stations scattered along-strike from 91.5° to 98°E near the Kunlun-Qaidam boundary show that the width of the overlapping region ranges from ~10-40 km at different locations along the boundary, and near Golmud the deeper reflector may dip northwards. The crustal thickness change appears unrelated to the strike-slip North Kunlun Fault. At depths shallower than 100 km, we also see no evidence of southward subduction of Eurasian lithosphere. Crustal velocities and impedance contrasts suggest that instead weak Tibetan lower crust is injected northward beneath stronger Qaidam crust.
PC-based attendees: Windows® 8, 7, Vista, XP or 2003 Server
Mac®-based attendees: Mac OS® X 10.6 or newer
Mobile attendees: iPhone®, iPad®, Android™ phone or Android tablet
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