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Processing, analysis, and interpretation of deep seismic reflection data from the Tibetan plateau.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Processing, analysis, and interpretation of deep seismic reflection data from the Tibetan plateau./
Author:	Alsdorf, Douglas Eric.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1996,
Description:	189 p.
Notes:	Source: Dissertations Abstracts International, Volume: 58-04, Section: B.
Contained By:	Dissertations Abstracts International58-04B.
Subject:	Geophysics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9639611
ISBN:	9780591055696

Processing, analysis, and interpretation of deep seismic reflection data from the Tibetan plateau.
Alsdorf, Douglas Eric.

Processing, analysis, and interpretation of deep seismic reflection data from the Tibetan plateau. - Ann Arbor : ProQuest Dissertations & Theses, 1996 - 189 p.

Source: Dissertations Abstracts International, Volume: 58-04, Section: B.

Thesis (Ph.D.)--Cornell University, 1996.

This item must not be sold to any third party vendors.

The large expanse of high altitude, low relief, and $\\sim$70 km thick crust of the Tibetan plateau is very anomalous compared to most other continental regions. Deep seismic data were collected by Project INDEPTH across the south-central Tibetan plateau to investigate its lithospheric structure in order to help better define the mechanisms of crustal thickening and plateau uplift. Analysis of the deeper portions of profiles collected within the Tethyan Himalaya (Tib-1 and 2) suggests that a dipping reflection "fabric" may be present in the upper mantle. Reflections from the crustal portions of seismic data from the Lhasa terrane can be interpreted, although not uniquely, as indicating significant internal shortening of the crystalline basement. The analysis of the data collected beneath the Tethyan Himalaya includes correlation coefficient filtering, apparently applied here for the first time to seismic data. The filter compares adjacent traces or overlapping stack sections and passes the correlative signals, thus it is particularly effective for quantifying the identification of weak reflections. Qualitative analyses suggest that the reflections form a fabric at long travel times. Geometrical and velocity constraints are used to argue that the fabric is not easily associated with shallow artifacts (e.g., reflected surface waves). Instead, the fabric may correspond to structures within the mantle. The fabric strike (N63E) and dip (44$\\sp\\circ$ N27W) is significantly oblique to the $\\sim$EW strike and low-angle dip ($\\sim$10$\\sp\\circ)$ of crustal deformation. The discordance between crustal and mantle orientations suggests that the fabric may predate the collision of India with Tibet, hence marking a previous deformation of the Indian lithosphere. However, if the fabric is the result of collision, the discordance suggests that mantle deformation is somehow decoupled from crustal deformation. The profiles recorded over the Lhasa terrane include reflections interpreted as marking a large, crustal-scale duplex (minimum shortening of 40 km and thickening of 14 km) within the basement. A steeply, north dipping reflection may mark the Zangbo suture at lower crustal depths, in which case, very little Indian crust has extended beneath the Lhasa terrane. If these interpretations are correct, then they support plateau formation models emphasizing internal crustal shortening but with decoupling and underthrusting of India's mantle-lid.

ISBN: 9780591055696Subjects--Topical Terms:

535228
Geophysics.
Subjects--Index Terms:

Himalaya

Processing, analysis, and interpretation of deep seismic reflection data from the Tibetan plateau.
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500 $a Source: Dissertations Abstracts International, Volume: 58-04, Section: B.
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520 $a The large expanse of high altitude, low relief, and $\\sim$70 km thick crust of the Tibetan plateau is very anomalous compared to most other continental regions. Deep seismic data were collected by Project INDEPTH across the south-central Tibetan plateau to investigate its lithospheric structure in order to help better define the mechanisms of crustal thickening and plateau uplift. Analysis of the deeper portions of profiles collected within the Tethyan Himalaya (Tib-1 and 2) suggests that a dipping reflection "fabric" may be present in the upper mantle. Reflections from the crustal portions of seismic data from the Lhasa terrane can be interpreted, although not uniquely, as indicating significant internal shortening of the crystalline basement. The analysis of the data collected beneath the Tethyan Himalaya includes correlation coefficient filtering, apparently applied here for the first time to seismic data. The filter compares adjacent traces or overlapping stack sections and passes the correlative signals, thus it is particularly effective for quantifying the identification of weak reflections. Qualitative analyses suggest that the reflections form a fabric at long travel times. Geometrical and velocity constraints are used to argue that the fabric is not easily associated with shallow artifacts (e.g., reflected surface waves). Instead, the fabric may correspond to structures within the mantle. The fabric strike (N63E) and dip (44$\\sp\\circ$ N27W) is significantly oblique to the $\\sim$EW strike and low-angle dip ($\\sim$10$\\sp\\circ)$ of crustal deformation. The discordance between crustal and mantle orientations suggests that the fabric may predate the collision of India with Tibet, hence marking a previous deformation of the Indian lithosphere. However, if the fabric is the result of collision, the discordance suggests that mantle deformation is somehow decoupled from crustal deformation. The profiles recorded over the Lhasa terrane include reflections interpreted as marking a large, crustal-scale duplex (minimum shortening of 40 km and thickening of 14 km) within the basement. A steeply, north dipping reflection may mark the Zangbo suture at lower crustal depths, in which case, very little Indian crust has extended beneath the Lhasa terrane. If these interpretations are correct, then they support plateau formation models emphasizing internal crustal shortening but with decoupling and underthrusting of India's mantle-lid.
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