Surface‐Wave Dispersion in Partially Saturated Soils: The Role of Capillary Forces

SUMMARY Seismic body wave traveltime tomography and surface wave dispersion tomography have been used widely to characterize earthquakes and to study the subsurface structure of the Earth. Since these types of problem are often significantly non-linear and have non-unique solutions, Markov chain Monte Carlo methods have been used to find probabilistic solutions. Body and surface wave data are usually inverted separately to produce independent velocity models. However, body wave tomography is generally sensitive to structure around the subvolume in which earthquakes occur and produces limited resolution in the shallower Earth, whereas surface wave tomography is often sensitive to shallower structure. To better estimate subsurface properties, we therefore jointly invert for the seismic velocity structure and earthquake locations using body and surface wave data simultaneously. We apply the new joint inversion method to a mining site in the United Kingdom at which induced seismicity occurred and was recorded on a small local network of stations, and where ambient noise recordings are available from the same stations. The ambient noise is processed to obtain inter-receiver surface wave dispersion measurements which are inverted jointly with body wave arrival times from local earthquakes. The results show that by using both types of data, the earthquake source parameters and the velocity structure can be better constrained than in independent inversions. To further understand and interpret the results, we conduct synthetic tests to compare the results from body wave inversion and joint inversion. The results show that trade-offs between source parameters and velocities appear to bias results if only body wave data are used, but this issue is largely resolved by using the joint inversion method. Thus the use of ambient seismic noise and our fully non-linear inversion provides a valuable, improved method to image the subsurface velocity and seismicity.

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Reliable workflow for inversion of seismic receiver function and surface wave dispersion data: a “13 BB Star” case study

Journal of Seismology ◽

10.1007/s10950-019-09888-1 ◽

2019 ◽

Vol 24 (1) ◽

pp. 101-120

Author(s):

Kajetan Chrapkiewicz ◽

Monika Wilde-Piórko ◽

Marcin Polkowski ◽

Marek Grad

Keyword(s):

Surface Wave ◽

Inverse Problems ◽

Receiver Function ◽

Joint Inversion ◽

Wave Dispersion ◽

Receiver Functions ◽

P Wave ◽

Surface Wave Dispersion ◽

Phase Velocity Dispersion ◽

Wide Range

AbstractNon-linear inverse problems arising in seismology are usually addressed either by linearization or by Monte Carlo methods. Neither approach is flawless. The former needs an accurate starting model; the latter is computationally intensive. Both require careful tuning of inversion parameters. An additional challenge is posed by joint inversion of data of different sensitivities and noise levels such as receiver functions and surface wave dispersion curves. We propose a generic workflow that combines advantages of both methods by endowing the linearized approach with an ensemble of homogeneous starting models. It successfully addresses several fundamental issues inherent in a wide range of inverse problems, such as trapping by local minima, exploitation of a priori knowledge, choice of a model depth, proper weighting of data sets characterized by different uncertainties, and credibility of final models. Some of them are tackled with the aid of novel 1D checkerboard tests—an intuitive and feasible addition to the resolution matrix. We applied our workflow to study the south-western margin of the East European Craton. Rayleigh wave phase velocity dispersion and P-wave receiver function data were gathered in the passive seismic experiment “13 BB Star” (2013–2016) in the area of the crust recognized by previous borehole and refraction surveys. Final models of S-wave velocity down to 300 km depth beneath the array are characterized by proximity in the parameter space and very good data fit. The maximum value in the mantle is higher by 0.1–0.2 km/s than reported for other cratons.

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Surface wave dispersion measurements from ambient seismic noise analysis in Italy

Geophysical Journal International ◽

10.1111/j.1365-246x.2009.04476.x ◽

2010 ◽

Vol 180 (3) ◽

pp. 1242-1252 ◽

Cited By ~ 41

Author(s):

Hongyi Li ◽

Fabrizio Bernardi ◽

Alberto Michelini

Keyword(s):

Surface Wave ◽

Seismic Noise ◽

Noise Analysis ◽

Wave Dispersion ◽

Ambient Seismic Noise ◽

Surface Wave Dispersion

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Surface Wave Dispersion Imaging Using Improved τ-p Transform Approach

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.1196 ◽

2013 ◽

Vol 353-356 ◽

pp. 1196-1202 ◽

Cited By ~ 2

Author(s):

Jian Qi Lu ◽

Shan You Li ◽

Wei Li

Keyword(s):

Surface Wave ◽

Phase Shift ◽

Dispersion Curve ◽

Wave Dispersion ◽

S Wave ◽

Surface Wave Dispersion ◽

Narrow Frequency Range ◽

Channel Analysis ◽

Rayleigh Wave Dispersion

Surface wave dispersion imaging approach is crucial for multi-channel analysis of surface wave (MASW). Because the resolution of inversed S-wave velocity and thickness of a layer are directly subjected to the resolution of imaged dispersion curve. The τ-p transform approach is an efficient and commonly used approach for Rayleigh wave dispersion curve imaging. However, the conventional τ-p transform approach was severely affected by waves amplitude. So, the energy peaks of f-v spectrum were mainly gathered in a narrow frequency range. In order to remedy this shortage, an improved τ-p transform approach was proposed by this paper. Comparison has been made between phase shift and improved τ-p transform approaches using both synthetic and in situ tested data. Result shows that the dispersion image transformed from proposed approach is superior to that either from conventionally τ-p transform or from phase shift approaches.

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