[1] We constrain the geometry and P and S velocity structure of a low-velocity anomaly in the lower mantle beneath southern Africa (we term it the ‘‘African Anomaly’’) on the basis of forward traveltime and waveform modeling of seismic data sampling a great arc across the anomaly from the East Pacific Rise to the Japan Sea. Our collected data set consists of direct S, direct P, Sdiff, ScS, PcP,...

We used continuous recordings in Sichuan, China to track the temporal change in elastic properties of the medium, namely the seismic speed, at a regional scale in a 2 year period which includes the great Wenchuan Mw 7.9 earthquake. The data are recorded by a temporary network of 156 broad-band seismographs, in a 200km × 200km region that covers the southern 2/3 of the fault system activated dur...

Time migration velocity analysis can be performed by velocity continuation, an incremental process that transforms migrated seismic sections according to changes in the migration velocity. Velocity continuation enhances residual normal moveout correction by properly taking into account both vertical and lateral movements of events on seismic images. Finite-difference and spectral algorithms pro...

Time-migration velocity analysis can be performed by velocity continuation, an incremental process that transforms migrated seismic sections according to changes in the migration velocity. Velocity continuation enhances residual normal moveout correction by properly taking into account both vertical and lateral movements of events on seismic images. Finite-difference and spectral algorithms pro...

Travel times of 11,612 Pn arrivals collected from 7675 earthquakes are inverted to image the uppermost mantle velocity and anisotropy structure beneath the southern half of the Iberian Peninsula and surrounding regions. Pn phases are routinely identified and picked for epicentral distances from 200 to 1200 km. The method used in this study allows simultaneous imaging of variations of Pn velocit...

Seismic image and velocity models were obtained from a newly conducted seismic survey around the Integrated Ocean Drilling Program (IODP) Japan Trench Fast Drilling Project (JFAST) drill site in the Japan Trench. Pre-stack depth migration (PSDM) analysis was applied to the multichannel seismic reflection data to produce an accurate depth seismic profile together with a P wave velocity model alo...

Earthen dams and levees are prone to progressive failure through internal erosion of their structure. Internal erosion is often invisible to current methods of inspection until it manifests itself at the exterior surface. This study focuses on the novel use of passive seismic interferometry to monitor temporal changes in earthen embankments caused by internal erosion. This technique uses the am...

Information about reservoir properties usually comes from two sources: seismic data and well logs. The former provide an indirect, low resolution image of rock velocity and density. The latter provide direct, high resolution (but laterally sparse) sampling of these and other rock parameters. An important problem in reservoir characterization is how best to combine these data sets, allowing the ...

Image segmentation can automatically delineate salt bodies in seismic data, an otherwise human-intensive and time-consuming task. In many instances, current segmentation algorithms successfully pick salt boundaries; a logical extension of such work is to apply these methods to the task of building and updating seismic velocity models. We apply image segmentation tools in conjunction with sedime...

We have developed a case study of crosshole seismic tomography with a cross-firing geometry in which seismic sources were placed in two vertical boreholes alternatingly and receiver arrays were placed in another vertical borehole. There are two crosshole seismic data sets in a conventional sense. These two data sets are used jointly in seismic tomography. Because the local sediment is dominated...