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Webinar - Seismic imaging of the crust using Bayesian joint Inversion of teleseismic P-wave coda autocorrelation waveforms.

Event Type

Event Date

Tuesday, February 2, 2021

Event Location

Event Address


Event Start

1230 AWST

Event End

1330 AWST

Event Details

On Tuesday 2 February, 3:30pm AEDT FedEx is bringing you a talk by Dr Mehdi Tork Qashqai from the CSIRO on Seismic imaging of the crust using Bayesian joint Inversion of teleseismic P-wave coda autocorrelation waveforms.

Deep crustal-scale structures are critical for controlling and development of a wide range of mineral deposits. Incoming seismic waves generated from teleseismic earthquakes can be used to image the deep crustal structures. Traveltimes of the teleseismic P and mode-converted S-waves and their reverberations place a tight constraint on the Vp/Vs ratio, and their amplitude ratio provides tight bounds on the P and S wave velocity jumps across the main discontinuities/boundaries in the subsurface structure below a seismic receiver. Teleseismic P-to-S converted waveforms have been used for decades to estimate the shear-wave velocity of the subsurface and depths of major discontinuities below a seismic receiver through a method known as the P receiver functions. In this presentation, a new and alternative approach is presented. Waveforms associated with the P and all mode-converted shear waves are extracted by the autocorrelation of the teleseismic P-wave coda recorded on the radial and vertical component of a three-component receiver. Then, these waveforms are jointly inverted using a probabilistic joint inversion framework to simultaneously estimate seismic properties of the crust (Vp, Vs and Vp/Vs). This approach is particularly useful when there are no high-quality and reliable receiver function waveforms. This approach is cost-effective and can be used in conjunction with the inversion of receiver function, or the deep active seismic reflection profiling to obtain additional/complementary information on the subsurface structure, especially at middle and lower crustal depths where the deep seismic reflection method has penetration problem. In this presentation, I will show some synthetic and real data examples to confirm the feasibility of this imaging technique and also to encourage further application of this approach.



In November 2012, Mehdi joined the PhD program at Geodynamic and Geophysics group at Macquarie university in Sydney, Australia. His research focused on the development and implementation of a multi-parameter geophysical inverse modelling tool known as “LitMod”. In August 2016, Mehdi completed his PhD thesis entitled “Multi-observable Probabilistic Inversion for the Thermochemical Structure of the Lithosphere". Prior to his doctoral study, he was working in the oil and gas exploration industry for 6 years as a seismic processing and team leader geophysicist, delivering processing, imaging, and quantitative interpretation of seismic data. He joined the CSIRO Deep Earth Imaging Future Science Platform (DEI FSP) in July 2017 as a postdoctoral fellow. He is currently a research scientist at CSIRO DEI FSP and his main research in the “Geoscience Imaging” pillar of the DEI research is focused on the developing and application of new passive seismic imaging approaches to obtain better tomographic models of subsurface structure across multiple scales (e.g., from exploration-scale to lithospheric-scale). 


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