Characterizing near-surface structures at the Ostia archaeological site based on instantaneous-phase coherency inversion

Traditional least-squares full-waveform inversion (FWI) suffers from severe local minima problems in case of the presence of strongly dispersive surface waves. Additionally, recorded wavefields are often characterized by amplitude errors due to varying source coupling and incorrect 3D-to-2D geometrical-spreading correction. Thus, least...

A numerical study on waves induced by wheel-rail contact

Recent finite element (FE) simulations have revealed the generation and propagation of waves in rail surfaces induced by wheel-rail frictional rolling. These waves have rarely been addressed in the literature. This paper presents an in-depth analysis of these waves, aiming to give new insights into the contact mechanics, a research area in...

Estimating the location of a tunnel using correlation and inversion of Rayleigh wave scattering

The investigation of near-surface scatterers, such as cavities, tunnels, abandoned mine shafts, and buried objects, is important to mitigate geohazards and environmental hazards. By inversion of travel times of cross-correlated scattered waves, due to the incident Rayleigh waves, we estimate the location of a near-surface tunnel from seismic...

Medium characterization from interface-wave impedance and ellipticity using simultaneous displacement and pressure measurements

The interface-wave impedance and ellipticity are wave attributes that interrelate the full waveforms as observed in different components. For each of the fluid/elastic-solid interface waves, i.e., the pseudo-Rayleigh (pR) and Stoneley (St) waves, the impedance and ellipticity are found to have different functional dependencies on Young’s modulus...

Source depopulation potential and surface-wave tomography using a crosscorrelation method in a scattering medium

We use seismic prospecting data on a 40 × 40 regular grid of sources and receivers deployed on a 1 km × 1 km area to assess the feasibility and advantages of velocity analysis of the shallow subsurface by means of surface-wave tomography with Green's functions estimated from crosscorrelation. In a first application we measure Rayleigh-wave...

On wavemodes at the interface of a fluid and a fluid-saturated poroelastic solid

Pseudo interface waves can exist at the interface of a fluid and a fluid-saturated poroelastic solid. These waves are typically related to the pseudo-Rayleigh pole and the pseudo-Stoneley pole in the complex slowness plane. It is found that each of these two poles can contribute (as a residue) to a full transient wave motion when the...

Mean grain size mapping with single-beam echo sounders

Echo energies of single-beam echo sounders are inverted for the sediment mean grain size via a combination of theoretical and empirical relationships. In situ measurements of the seafloor mass density have revealed the presence of a thin transition layer between the water and the sediment. Within this layer, which has a thickness of order 1 cm,...