Seismic images reconstructed by migration from seismic data recorded at the surface represent the earth structure at every location in the subsurface. The data are remapped into the subsurface by using a wave equation and an estimate of the earth velocity. The velocity model is of great importance for obtaining accurate seismic images and for understanding the subsurface reservoir properties an...

Echo-reconstruction techniques for non-intrusive imaging have wide application, from subsurface and underwater imaging to medical and industrial diagnostics. The techniques are based on experiments in which a collection of short acoustic or electromagnetic impulses, emitted at the surface, illuminate a certain volume and are backscattered by inhomogeneities of the medium. The inhomogeneities ac...

A method to estimate S-wave interval velocity, using P-S seismic data is presented. The method is composed of three steps. First, the P-S data are converted to a relative change in S-velocity section. The section is then linearized. Constrained inversion is used to convert this last section to S-interval velocity. To illustrate the method, the S velocity of a field data set was derived, and a V...

the present paper studies the possibility of propagation of torsional surface waves in an inhomogeneous anisotropic layer lying between two heterogeneous half-spaces (upper and lower half-space). both the half-spaces are assumed to be under compressive initial stress. the study reveals that under the assumed conditions, a torsional surface wave propagates in the medium. the dispersion relation ...

GABRIELS, P., SNIEDER, . and NOLET, G. 1987, In Situ Measurement of Shear-Wave Velocity in Sediments with Higher-Mode Rayleigh Waves, 35,187-196. A seismic survey was carried out on a tidal flat in the SW-Netherlands in order to determine shear-wave velocities in sediments by means of higher-mode Rayleigh waves. The dispersion properties of these Rayleigh waves were measured in the 2-D amplitud...

Waveform inversion is a velocity-model-building technique based on full waveforms as the input and seismic wavefields as the information carrier. Conventional waveform inversion is implemented in the data domain. However, similar techniques referred to as image-domain wavefield tomography can be formulated in the image domain and use a seismic image as the input and seismic wavefields as the in...

S U M M A R Y One way of developing a wave-equation approach to seismic imaging is based on the concept of downward continuation of observed surface reflection data. Seismic imaging is typically based on the single scattering approximation, and assumes the knowledge of a smooth background model in which the mentioned downward continuation is carried out using the double-squareroot (DSR) equatio...

[1] We present a new crustal seismic velocity model for southern California derived from P and S arrival times from local earthquakes and explosions. To reduce the volume of data and ensure a more uniform source distribution, we compute ‘‘composite event’’ picks for 2597 distributed master events that include pick information for other events within spheres of 2 km radius. The approach reduces ...

We analyzed vertical component short-period ScP waveforms for 26 earthquakes occurring in the Tonga-Fiji trench recorded at the Alice Springs Array in central Australia. These waveforms show strong precursory and postcursory seismic arrivals consistent with ultralow-velocity zone (ULVZ) layering beneath the Coral Sea. We used the Viterbi sparse spike detection method to measure differential tra...