Optimized Experimental Design in the Context of Seismic Full Waveform Inversion and Seismic Waveform Imaging

As the volume of available seismic waveform data increases, the responsibility to use the data in an effective way emerges. This requires computational efficiency as well as maximizing the exploitation of the information associated with the data.In this contribution, we present a long-wavelength Earth model, created by using the data recorded from over a thousand earthquakes, starting from a simple one-dimensional background (PREM). The model is constructed with an accelerated full-waveform inversion (FWI) method which can seamlessly include large data volumes with a significantly reduced computational overhead. Although we present a long-wavelength model, the approach has the potential to go to much higher frequencies, while maintaining a reasonable cost.Our approach combines two novel FWI variants. (1) The dynamic mini-batch approach which uses adaptively defined subsets of the full dataset in each iteration, detaching the direct scaling of inversion cost from the number of earthquakes included. (2) Wavefield-adapted meshes which utilize the azimuthal smoothness of the wavefield to design meshes optimized for each individual source location. Using wavefield adapted meshes can drastically reduce the cost of both forward and adjoint simulations as well as it makes the scaling of the computing cost to modelled frequencies more favourable.

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Sinkhole detection with 3D full seismic waveform tomography

Geophysics ◽

10.1190/geo2019-0490.1 ◽

2020 ◽

Vol 85 (5) ◽

pp. B169-B179

Author(s):

Majid Mirzanejad ◽

Khiem T. Tran ◽

Michael McVay ◽

David Horhota ◽

Scott J. Wasman

Keyword(s):

Wave Equations ◽

Waveform Inversion ◽

Field Tests ◽

Waveform Analysis ◽

Full Waveform Inversion ◽

3D Seismic ◽

Data Set ◽

Full Waveform ◽

Seismic Waveform ◽

Elastic Wave Equations

Sinkhole collapse may result in significant property damage and even loss of life. Early detection of sinkhole attributes (buried voids, raveling zones) is critical to limit the cost of remediation. One of the most promising ways to obtain subsurface imaging is 3D seismic full-waveform inversion. For demonstration, a recently developed 3D Gauss-Newton full-waveform inversion (3D GN-FWI) method is used to detect buried voids, raveling soils, and characterize variable subsurface soil/rock layering. It is based on a finite-difference solution of 3D elastic wave equations and Gauss-Newton optimization. The method is tested first on a data set constructed from the numerical simulation of a challenging synthetic model and subsequently on field data collected from two separate test sites in Florida. For the field tests, receivers and sources are placed in uniform 2D surface grids to acquire the seismic wavefields, which then are inverted to extract the 3D subsurface velocity structures. The inverted synthetic results suggest that the approach is viable for detecting voids and characterizing layering. The field seismic results reveal that the 3D waveform analysis identified a known manmade void (plastic culvert), unknown natural voids, raveling, as well as laterally variable soil/rock layering including rock pinnacles. The results are confirmed later by standard penetration tests, including depth to bedrock, two buried voids, and a raveling soil zone. Our study provides insight into the application of the 3D seismic FWI technique as a powerful tool in detecting shallow voids and other localized subsurface features.

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Optimized experimental design for seismic full waveform inversion: A computationally efficient method including a flexible implementation of acquisition costs

Geophysical Prospecting ◽

10.1111/1365-2478.13040 ◽

2020 ◽

Vol 69 (1) ◽

pp. 152-166

Author(s):

Valérie Krampe ◽

Pascal Edme ◽

Hansruedi Maurer

Keyword(s):

Experimental Design ◽

Efficient Method ◽

Waveform Inversion ◽

Full Waveform Inversion ◽

Computationally Efficient ◽

Full Waveform ◽

Acquisition Costs

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3-D seismic full-waveform inversion of the Taurus-Zagros region in Iran and Turkey

10.5194/egusphere-egu2020-13470 ◽

2020 ◽

Author(s):

Neda Masouminia ◽

Dirk-Philip van Herwaarden ◽

Sölvi Thrastarson ◽

Habib Rahimi ◽

Lion Krischer ◽

...

Keyword(s):

Upper Mantle ◽

Waveform Inversion ◽

Spectral Element ◽

Earth Model ◽

Model Parameters ◽

Full Waveform Inversion ◽

Geophysical Research ◽

Seismic Stations ◽

Full Waveform ◽

Seismic Waveform

We present an interpretation of a 3-D velocity model resulting from a regional analysis of earthquake waveforms. This model contains 3-D structure of the crust and upper mantle beneath the Arabian-Eurasian collision zone in eastern Turkey and Iran. We use full-waveform inversion (FWI) of three-component recordings from permanent networks. FWI can exploit all parts of a seismogram, including body and multi-mode surface waves in a broad range of frequencies. This allows us to constrain seismic structure of both the crust and the upper mantle.In our method we simulate 3-D visco-elastic wavefields using a spectral-element method (Fichtner et al,2018). Our numerical mesh honors topography of the surface. We compare observed and synthetic waveforms using time-frequency phase misfits. Using adjoint techniques, we then compute sensitivity kernels with respect to the model parameters, which are VSV, VSH, VPV, and VPH. Finally, the kernels enable the iterative solution of the nonlinear inverse problem with the help of the L-BFGS algorithm and without a need for crustal corrections.For this study we obtained seismic waveform data of 59 earthquakes within the magnitude range of Mw 4.5 to 6.3 that occurred in the region between 2012 and 2016. These events were recorded by 398 broadband seismic stations belonging to the two national Iranian networks and freely available seismic stations of the Turkish Network, made available by IRIS. Starting from the first generation of the Collaborative Seismic Earth Model (Afanasiev et al.2019), we first constrained longer-wavelength structure. To this end, we considered 3-component recordings from a subset of 37 events in the period range from 50 to 80 s. This band was successively broadened by reducing the shorter period from 50 s to 40 s, and finally to 20 s. For each period band, the number and the length of measurement windows are increased; the number of events is also increased to 59 to use the complete dataset. After 46 iterations our model can explain recordings of events, which were not used in the inversion. The results provide to discuss about high-velocity anomaly beneath the Zagros and the shallow low velocities beneath Central Iran using cross-sections to investigate lateral variation of seismic velocity in the lithosphere.REFERENCESAfanasiev, M., Boehm, C., van Driel, M., Krischer, L., Rietmann, M., May, D. A., Knepley, M. G., Fichtner, A., 2019. Modular and flexible spectral-element waveform modelling in two and three dimensions. Geophysical Journal International 216, 1675-1692, doi: 10.1093/gji/ggy469.Fichtner, A., van Herwaarden, D.-P., Afanasiev, M., Simute, S., Krischer, L., Cubuk-Sabuncu, Y., Taymaz, T., Colli, L., Saygin, E., Villasenor, A., Trampert, J., Cupillard, P., Bunge, H.-P., Igel, H., 2018. The Collaborative Seismic Earth Model: Generation I. Geophysical Research Letters 45, doi: 10.1029/2018GL077338.

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