Abstract: The invention concerns a method for retrieving local near-surface material information including the steps of:—providing a group of receivers comprising at least one buried receiver and at least one surface receiver positioned either at or very near the Earth surface;—recording a seismic wavefield;—estimating a propagator from said recorded seismic wavefield;—inverting said propagator; and—retrieving said near-surface material information.

Abstract: A power tool includes vibration isolation material positioned between an engine shroud and a drive shaft housing. The vibration isolation material isolates the drive shaft housing from engine vibration for radial, axial, and torsional movement without utilizing intermediate components.

Abstract: A new approach is described based on reciprocity for estimating acquisition-related effects, which has several advantages over conventional surface-consistent processing techniques: (i) It can be applied to complete recordings, hence does not require the isolation of primary reflections in the data, (ii) no assumptions are imposed on the subsurface, and (iii) it is applicable to multi-component data. The application of reciprocity requires symmetric data acquisition, i.e. identical source and receiver patterns, identical locations, and the source orientations have to be identical to the receiver components. Besides reciprocity, additional constraints are required to determine the lateral source and receiver amplitude variations fully. Criteria based on minimizing total energy differences between adjacent common source and common receiver gathers, and in common offset panels of the medium response are applied.

Abstract: A method of processing seismic data that includes including first and second modes of seismic energy where the second mode has been generated by partial mode conversion of the first mode at a boundary face of a layer of the seabed includes the step of cross-correlating a trace acquired at a receiver and including events corresponding to the first mode with a trace acquired at the same receiver and including events corresponding to the second mode. An event in the cross-correlated data that corresponds to partial mode conversion is identified, and the amplitude of this event is normalised, for example relative to the amplitude of the peak in the cross-correlogram at zero time delay. Information about the effects of the static shift produced by the layer and/or about vector infidelity can be arrived from normalised cross-correlograms for receivers in a receiver array.

Abstract: A power tool includes vibration isolation material positioned between an engine shroud and a drive shaft housing. The vibration isolation material isolates the drive shaft housing from engine vibration for radial, axial, and torsional movement without utilizing intermediate components.

Abstract: A method for estimating near-surface material properties in the vicinity of a locally dense group of seismic receivers is disclosed. The method includes receiving seismic data that has been measured by a locally dense group of seismic receivers. Local derivatives of the wavefield are estimated such that the derivatives are centered at a single location preferably using the Lax-Wendroff correction. Physical relationships between the estimated derivatives including the free surface condition and wave equations are used to estimate near-surface material properties in the vicinity of the receiver group. Another embodiment of the invention is disclosed wherein the physical relationships used to estimate material properties are derived from the physics of plane waves arriving at the receiver group, and the group of receivers does not include any buried receivers.

Abstract: A system and method of creating a filter for use with locally dense seismic data is disclosed. The method includes obtaining survey geometry characteristics from a locally dense seismic survey. A filter is designed which uses spatial derivatives of the wavefield of order between (1) and the maximum order of spatial derivatives of the wavefield that can be estimated within a group. The filter can be designed so as to separate up/down going components, p/s components, or both up/down and p/s components. Partial derivatives in space and time of the wavefield can be calculated, using, for example, a taylor series expansion as an approximation. The seismic data is filtered by combining estimated near surface material properties, the seismic data, and the calculated partial derivatives.

Abstract: The invention concerns a method for retrieving local near-surface material information including the steps of:—providing a group of receivers comprising at least one buried receiver and at least one surface receiver positioned either at or very near the Earth surface;—recording a seismic wavefield;—estimating a propagator from said recorded seismic wavefield;—inverting said propagator; and—retrieving said near-surface material information.

Abstract: Seismic detection apparatus comprising seismic detection means capable of detecting a plurality of seismic components over a defined tetrahedral volume is provided. The seismic detection means comprises four three-component geophones. Seismic data acquired by the geophones is processed to separate P-wave components from S-wave components. The geophones are spaced apart by distances smaller than the wavelength of the detected seismic components. The apparatus may be used on surface or in a marine environment or transition zone. A method of processing seismic data is also provided comprising acquiring seismic data relating to a wavefield over a selected volume of acquisition, and measuring the curl and divergence of the wavefield from the seismic data, to thereby identify seismic components within the seismic data. Additionally, an apparatus and method for hydrocarbon exploration is disclosed for using three or more seismic receivers placed in a plane and spaced closely to each other.

Abstract: A method of determining seismic properties of a layer of the seabed, in particular a surface or near-surface layer (5), comprises directing seismic energy propagating in a first mode at a boundary face of the layer so as to cause partial mode conversion of the seismic energy at the boundary face. For example partial mode conversion may occur when seismic energy propagates upwards through the interface between a surface or near-surface layer (5) and the basement (6), owing to the difference in seismic properties between the surface or near-surface layer (5) and the basement (6). In the invention, the two modes of seismic energy—that is the initial mode and the mode generated by mode conversions at the interface—are received at a receiver. The difference in travel time of the two modes between the interface and the receiver is determined from the seismic data acquired by the receiver.

Abstract: A method for estimating near-surface material properties in the vicinity of a locally dense group of seismic receivers is disclosed. The method includes receiving seismic data that has been measured by a locally dense group of seismic receivers. Local derivatives of the wavefield are estimated such that the derivatives are centered at a single location preferably using the Lax-Wendroff correction. Physical relationships between the estimated derivatives including the free surface condition and wave equations are used to estimate near-surface material properties in the vicinity of the receiver group.

Abstract: A system and method of creating a filter for use with locally dense seismic data is disclosed. The method includes obtaining survey geometry characteristics from a locally dense seismic survey. A filter is designed which uses spatial derivatives of the wavefield of order between (1) and the maximum order of spatial derivatives of the wavefield that can be estimated within a group. The filter can be designed so as to separate up/down going components, p/s components, or both up/down and p/s components. Partial derivatives in space and time of the wavefield can be calculated, using, for example, a taylor series expansion as an approximation. The seismic data is filtered by combining estimated near surface material properties, the seismic data, and the calculated partial derivatives.

Abstract: A method and system for determining the location of a microseismic event is disclosed. An electromagnetic sensor measures the electromagnetic energy which is caused by a microseismic event. Seismic data from the microseismic event is measured and recorded using plurality of ground motion sensors. The time at which microseismic event occurred is estimated based at least in part on the time at which electromagnetic energy caused by the microseismic event is received by the electromagnetic sensor. The location of said source of the microseismic event is determined using the estimated occurrence time and the time at which the seismic energy arrived at the ground motion sensors. A method of triggering a seismic recording device is also disclosed. The electromagnetic energy from a microseismic event is measured and recorded using an electromagnetic sensor. The time at which the microseismic event occurred is estimated based on the measured electromagnetic energy.

Abstract: A Search Engine utilizing a method and system for efficient storage and retrieval of data. The system comprises a record file, an index file, a duplicate segment file and access to a network of computers. The index files contains locations of data items, pointers to other index files, or an empty designation. The index files are arrays that contain locations corresponding to a predetermined range of characters with which the data items may be formed. Data items are stored according to the character strings of each data item. The first portion of a data object is indexed according to the indexing method of the present invention while a second portion of the data object is indexed according to another known database technology, such as B-tree.

Abstract: Furniture units such as beds, sofas, wall units, modular furniture, including bookcase/desk combinations, as well as other combinations of the furniture units with a secure container or safe are disclosed. The framework of the furniture is formed of steel, welded or otherwise fastened, into an integral unit so as to house the safe within a cage of steel. The safe may be attached to the framework by a bolt or a lock not otherwise accessible from outside the interior of the safe.