Imaging Crustal Thickness Variation and Vp/Vs Ratio in Australia

Yadav, Alok (2019) Imaging Crustal Thickness Variation and Vp/Vs Ratio in Australia. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Alok Yadav (14MS073)) 14MS073.pdf - Submitted Version Restricted to Repository staff only Download (120MB)

Abstract

The Receiver Runction (RF) analysis is performed to examine the variations in Moho depth and Vp/Vs ratio in various regions of Australia. Receiver function (RF) observations and P-to-S conversions is employed at the Moho, to investigate the variations in Moho depth across regions of Australia and to know the nature of the transition between crust and mantle. The Australian continent is comprising of various age blocks ranging from as far back as Archean to the recent period. The western part of Australia is of Archean age having Pilbara craton, and a large Yilgarn craton. Gawler craton is in central South Australia. The central region of Australia is primarily belongs to Proterozoic age while the eastern Australia is of Phanerozoic age. Having different age blocks, it is good to study the Australian region to know the variation of Moho depth from old Archean parts in Western Australia to the Phanerozoic provinces in the eastern Australia. "Receiver function analysis is a seismic method utilizing the fact that teleseismic P-waves when at a particular incident angles encounter on subsurface boundary will result in refracted and reflected P and S waves". The generated P and S waves are the result of the local structure. The local effects can be isolated by deconvolution into a data series known as the receiver function. Data from 38 seismic stations covering whole Australia is used in the study. Zhu and Kanamori (2000) stacking algorithm is used to calculate Moho depth and Vp/Vs ratio. The inverse modelling is performed using neighbourhood algorithm to know the nature of the Moho, avg. Moho depth avg. Vp/Vs ratio. The results obtained from the two methods shows similarity for many stations but for some it shows significant difference. The Moho depth in the Archean region lies mainly in between 30-40 km and Vp/Vs ratio lies in 1.704 { 1.760. In the Proterozoic regions, the Moho depth varies significantly from 32-56 km showing thicker crustal thickness beneath most of the stations having Vp/Vs ratio from 1.716 { 1.776. On the other hand in Phanerozoic regions mainly in the east the Moho thickness lies in between range of 30-45 km and Vp/Vs ratio in between 1.715 { 1.780. The Archean region shows sharp crust mantle transition mainly in Pilbara region while for other regions nature of Moho changes, so it can not be generalised.

Actions (login required)

View Item