Early development of marine electromagnetic methods, dating back about 80 years, was driven largely by defense/military applications, and use for these purposes continues to this day. Deepwater, frequency-domain, electric dipole-dipole, controlled-source electromagnetic CSEM methods arose from academic studies of the oceanic lithosphere in the 1980s, and although the hydrocarbon exploration ind...

Previous authors have tried to image seismic reflectivity by crosscorrelating passive seismic data, and treating the resultant correlograms as active source seismograms. We provide a mathematical framework for working with passive seismic correlograms that is both appropriate for V (x , y, z) media, and arbitrary source location. Under this framework, correlograms can be migrated with an imagin...

The California Integrated Seismic Network uses a large array of expensive seismometers that measure ground motion. However, the network is unable to provide reliable real-time source estimation due to the sparseness of the sensors. The Community Seismic Network project at Caltech plans to create a dense seismic network by leveraging small, inexpensive accelerometers attached to personal compute...

in seismic exploration studies different types of techniques are used to recognize seismic features in terms of their temporal and spatial spectra. variations in frequency content are sensitive to subtle changes in reflection information (castro de matos et al., 2003). in this study the joint time-frequency analysis is used for seismic texture recognition. discrete wavelet transform (dwt) witho...

Using array analysis, the direction and distance to a seismic P wave source can be determined. However, individual arrays are limited in their geographical coverage and by their resolving capability, which is determined by the array aperture, configuration, and number of stations. We demonstrate these limitations on three large seismic arrays located in Japan, Europe, and California, and find t...

performance seismic evaluation is an important topic in earthquake engineering. in this regard, several methods have previously been developed and used. the main objective of present research is to evaluate two methods including “capacity spectrum method (csm)” and “improved capacity spectrum method (icsm)” in determination of seismic performance of concrete frames. for this purpose, several sa...

near-surface variations can be very complex and may distort amplitudes and arrival times of the reflections events from target reflectors. near-surface complexities include topographic variations, near-surface irregularities, variations in soil conditions and the weathered layer. these perturbations generally have a significant impact on seismic recordings. although there is a general agreement...

With seismic interferometry one can retrieve the response to a virtual source inside an unknown medium, if there is a receiver at the position of the virtual source. Using inverse scattering theory, we demonstrate that, for a 1D medium, the requirement of having an actual receiver inside the medium can be circumvented, going beyond seismic interferometry. In this case, the wavefield can be focu...

2-D elementspace and beamspaceextensions of Friedlander’s wideband interpolated root-MUSIC technique are applied to azimuthvelocity source location using real seismic data from the GERESS array (Germany). We demonstrate that 2-D interpolated rootMUSIC is able to estimate the parameters of a typical seismic source with a good accuracy. The use of interpolated root-MUSIC and its beamspace modific...

S U M M A R Y The recent discovery that the seismic normal modes of the Earth are excited to a nearly constant level during seismically quiet days (‘the hum of the Earth’) has lead to much speculation as to what drives the observed background in the absence of large earthquakes. Other authors have shown that the hum cannot be explained by the many small earthquakes occurring each day and have a...