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Seismic imaging of active continenta...

Ferris, Aaron.

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Seismic imaging of active continental breakup in the Woodlark rift system of Papua New Guinea.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Seismic imaging of active continental breakup in the Woodlark rift system of Papua New Guinea./
作者:	Ferris, Aaron.
面頁冊數:	127 p.
附註:	Adviser: Geoffrey A. Abers.
Contained By:	Dissertation Abstracts International68-03B.
標題:	Geophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3254458

Seismic imaging of active continental breakup in the Woodlark rift system of Papua New Guinea.
Ferris, Aaron.

Seismic imaging of active continental breakup in the Woodlark rift system of Papua New Guinea. - 127 p.

Adviser: Geoffrey A. Abers.

Thesis (Ph.D.)--Boston University, 2007.

For most of the earth, the lithosphere is a transient feature, experiencing various fates over time. In regions of continental breakup, continental lithosphere ruptures and new oceanic lithosphere forms. One of the few active examples of this process is the Woodlark rift system of Papua New Guinea, where rapid continental extension progresses along strike to seafloor spreading. From a 1999-2000 field expedition, the region's first measurements from earthquakes reveal the evolution of lithospheric structure and composition across this transition. In the continental rift portion, along strike of seafloor spreading, the crust is highly thinned and the mantle lithosphere is mostly eroded. Slow mantle seismic velocities suggest upwelling of hot asthenosphere below the crust. In the crust, seismic velocities indicate a bulk felsic to intermediate composition, similar to other continental regions, and preclude extensive additions of mantle-derived basaltic melts. In contrast, closer to the seafloor spreading, seismic velocities reflect a mafic, oceanic-like crust. The spatial limit of mafic crust demonstrates that the transition from broad rifting to localized seafloor spreading occurs across a narrow, 60-km wide zone. Magmatism, related to extension, does not appear to alter the crust until complete lithospheric rupture, even though asthenosphere upwells below the continental crust. From the modern limit of seafloor spreading, local seismicity forms a 100-km long and 10-km wide band through the compositional transition, reflecting strain localization and lithospheric weakening ahead of seafloor spreading. The seismic zone likely marks the future site of lithospheric rupture and oceanic lithosphere formation. Beneath Alaska, in a companion study, earthquake signals illuminate the Pacific plate lithosphere between 50 and 150 km depth subducting beneath the North America, the ultimate fate of oceanic lithosphere. Here, the nature of the earthquake signals require a complicated interface at the top of the lithosphere, which is 20 km thick with a seismic velocity 20% slower than the surrounding mantle. The interface is too thick to represent normal oceanic crust, as expected for Pacific plate lithosphere and proposed for other subduction zones. It likely represents a thick exotic terrane subducting along with the plate, the thickest subducting crust known so far.Subjects--Topical Terms:

535228
Geophysics.

Seismic imaging of active continental breakup in the Woodlark rift system of Papua New Guinea.
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