DOI: 10.1016/j.tecto.2021.228855
论文题名: Distinct lithospheres in the Bay of Bengal inferred from ambient noise and earthquake tomography
作者: Saha G.K. ; Rai S.S. ; Prakasam K.S. ; Gaur V.K.
刊名: Tectonophysics
ISSN: 00401951
出版年: 2021
卷: 809 语种: 英语
中文关键词: Ambient noise
; Bay of Bengal
; Lithosphere
; Surface wave
英文关键词: Acoustic noise
; Acoustic wave velocity
; Boundary layer flow
; Boundary layers
; Earthquakes
; Image enhancement
; Shear waves
; Structural geology
; Wave propagation
; Conductive cooling
; Cross correlations
; Different origins
; Minimum velocities
; Rayleigh wave group velocities
; Shear wave velocity
; Thermal boundary layer
; Velocity structure
; Shear flow
; ambient noise
; earthquake
; lithospheric structure
; oceanic crust
; Rayleigh wave
; S-wave
; seismic tomography
; seismic velocity
; upper mantle
; velocity structure
; Bay of Bengal
; Indian Ocean
英文摘要: We present an improved 3-D shear wave velocity image of the uppermost mantle beneath the Bay of Bengal (BoB), the Bengal basin and the adjoining Indian shield to their west. Shear wave velocities were inverted from fundamental mode Rayleigh wave group velocities calculated along 21,600 crisscrossing paths from cross correlation of ambient noise as well earthquake seismograms. This study shows the hitherto unsuspected existence of distinct lithospheres in the eastern and western Bay of Bengal, on either side of 86° E longitude, but understandable in terms of their different origins and ages. The western Bay of Bengal, with greater than 120 km thick layered lithosphere has a shear wave velocity of 4.7 km/s beyond the depth of 90 km. This velocity structure is in lateral continuation with the high velocity in the adjacent cratonic India. The lithosphere thickening can be explained to be the result of conductive cooling of an oceanic plate with a temperature of 1300 ± 50 °C at its base. The remarkable similarity between the velocity structure of the western BoB and the adjoining Indian craton, which could be fortuitous, however, suggests the untested possibility that the fracture plane mediating the initial break-up of India from Antarctica might have been inclined towards the former creating asymmetrically spreading oceanic crust over a cratonic upper mantle. The eastern Bay of Bengal (BoB), in contrast, has thinner lithosphere (60–75 km) with minimum velocity of ~4.2 km/s which is anomalously low for an old ocean. This significant thinning could have been caused by a number of factors such as reheating of the original lithosphere arising from a thermal boundary layer instability or westward flow of mantle due to slab rollback of subducting Indian lithosphere in the Andaman arc. © 2021 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/170895
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth and Climate Science, IISER Pune, Homi Bhabha Road, Pune, 411008, India; #2-19-22/2, Street # 4, Kalyanapuri, Uppal, Hyderabad, 500039, India; CSIR- Fourth Paradigm Institute, Bangalore, India
Recommended Citation:
Saha G.K.,Rai S.S.,Prakasam K.S.,et al. Distinct lithospheres in the Bay of Bengal inferred from ambient noise and earthquake tomography[J]. Tectonophysics,2021-01-01,809