Abstract: A method for estimating uncertainties in determining hypocenters of seismic events occurring in subsurface formations according to one aspect includes determining estimates of event locations by choosing local peaks in summed amplitude of seismic energy detected by an array of sensors disposed above an area of the subsurface to be evaluated. For each peak, the following is performed: recomputing the summed amplitude response for a selected set of points of comprising small perturbations in time and space from the estimated event locations; computing second derivatives of log likelihood function from the stacked responses at the estimated location and the perturbed locations; assembling the second derivatives into a Fisher information matrix; computing an inverse of the Fisher information matrix; determining variances of estimated parameters from the elements from the diagonal of the inverted matrix; and computing standard deviations of the estimated parameters by calculating a square root of the variances.

Abstract: A method for passive seismic imaging includes entering into a programmable computer seismic signals measured at a plurality of spaced apart locations above a volume of Earth's subsurface to be evaluated. The signals are measured at each location along different directions to enable resolution of motion in three orthogonal directions. A seismic moment tensor is determined for at least one seismic event occurring in the subsurface from the measured seismic signals. Divergence-free transverse) and curl-free longitudinal components of a source term are determined from the moment tensor, seismic velocities, and the measured seismic signals. An image is generated at at least one point in the subsurface using the determined components.

Abstract: A method for estimating uncertainties in determining hypocenters of seismic events occurring in subsurface formations according to one aspect includes determining estimates of event locations by choosing local peaks in summed amplitude of seismic energy detected by an array of sensors disposed above an area of the subsurface to be evaluated. For each peak, the following is performed: recomputing the summed amplitude response for a selected set of points of comprising small perturbations in time and space from the estimated event locations; computing second derivatives of log likelihood function from the stacked responses at the estimated location and the perturbed locations; assembling the second derivatives into a Fisher information matrix; computing an inverse of the Fisher information matrix; determining variances of estimated parameters from the elements from the diagonal of the inverted matrix; and computing standard deviations of the estimated parameters by calculating a square root of the variances.

Abstract: A method for passive seismic surveying includes deploying seismic sensors in a plurality of spatially distributed wellbores disposed above a volume of subsurface formations to be evaluated. The sensors in each wellbore form a line of sensors. Each sensor generate optical or electrical signals in response to seismic amplitude. The seismic signals from each sensor are recorded for a selected period of time. The response of the seismic sensor recordings is beam steered to at least one of a selected point and a selected volume in the subsurface. At least one microseismic event is identified in the beam steered response.

Abstract: A method of imaging the Earth's subsurface using passive seismic interferometry tomography includes detecting seismic signals from within the Earth's subsurface over a time period using an array of seismic sensors, the seismic signals being generated by seismic events within the Earth's subsurface. The method further includes adaptively velocity filtering the detected signals. The method further includes cross-correlating the velocity filtered seismic signals to obtain a reflectivity series at a position of each of the seismic sensors.

Abstract: A method for locating origin time, origin location and source mechanism of seismic events occurring in a selected volume of subsurface formations includes calculating a travel time from each possible origin location to each of a plurality of seismic receivers disposed above the volume in a selected pattern. A signal amplitude is measured by each receiver for each possible origin time at each possible origin location. The signal amplitude is determined from the continuously recorded data by calculating travel time delays for each possible origin location and origin time. The deviatoric moment tensors are determined from the signal amplitudes by moment tensor inversion restricted to deviatoric moment tensors. A norm for each deviatoric moment tensor is generated. An origin time, origin position and source mechanism of a seismic event is determined wherein any norm exceeds a selected threshold.

Abstract: A method for seismic event mapping includes adaptively velocity filtering seismic signals recorded at selected positions. The velocity filtered signals are transformed into a domain of possible spatial positions of a source of seismic events. An origin in spatial position and time of at least one seismic event is determined from space and time distribution of at least one attribute of the transformed seismic data.

Abstract: A method for passive seismic surveying includes deploying seismic sensors in a plurality of spatially distributed wellbores disposed above a volume of subsurface formations to be evaluated. The sensors in each wellbore form a line of sensors. Each sensor generate optical or electrical signals in response to seismic amplitude. The seismic signals from each sensor are recorded for a selected period of time. The response of the seismic sensor recordings is beam steered to at least one of a selected point and a selected volume in the subsurface. At least one microseismic event is identified in the beam steered response.

Abstract: A method for seismic event mapping includes selecting a plurality of subvolumes representing possible locations of origin of a seismic event in the Earth's subsurface. For each subvolume a plurality of possible directions of motion of subsurface formations is selected. For each subvolume and each possible direction of motion, polarity correction is applied to seismic signals recorded at a plurality of positions proximate a volume of the Earth's subsurface to be evaluated. The polarity correction is based on the direction of motion and the position of each seismic sensor with respect to the subvolume. The recorded, polarity corrected seismic signal recordings are time aligned. The time aligned recordings are summed. A most likely direction of motion and subvolume position are determined based on a selected attribute of the summed, time aligned seismic signals.

Abstract: A method for seismic event mapping includes selecting a plurality of subvolumes representing possible locations of origin of a seismic event in the Earth's subsurface. For each subvolume a plurality of possible directions of motion of subsurface formations is selected. For each subvolume and each possible direction of motion, polarity correction is applied to seismic signals recorded at a plurality of positions proximate a volume of the Earth's subsurface to be evaluated. The polarity correction is based on the direction of motion and the position of each seismic sensor with respect to the subvolume. The recorded, polarity corrected seismic signal recordings are time aligned. The time aligned recordings are summed. A most likely direction of motion and subvolume position are determined based on a selected attribute of the summed, time aligned seismic signals.

Abstract: A method for seismic event mapping includes adaptively velocity filtering seismic signals recorded at selected positions. The velocity filtered signals are transformed into a domain of possible spatial positions of a source of seismic events. An origin in spatial position and time of at least one seismic event is determined from space and time distribution of at least one attribute of the transformed seismic data.

Abstract: A method of imaging the Earth's subsurface using passive seismic interferometry tomography includes detecting seismic signals from within the Earth's subsurface over a time period using an array of seismic sensors, the seismic signals being generated by seismic events within the Earth's subsurface. The method further includes adaptively velocity filtering the detected signals. The method further includes cross-correlating the velocity filtered seismic signals to obtain a reflectivity series at a position of each of the seismic sensors.

Abstract: A method for determining seismic anisotropy of subsurface rock formations includes measuring passive seismic signals at a plurality of locations above an area of the Earth's subsurface to be surveyed. The compressional- and shear-wave arrival times from at least one origin location of a seismic event occurring in the subsurface are determined from the measured seismic signals. The arrival times are inverted to obtain values of the seismic anisotropy parameters.

Abstract: A method for determining presence of seismic events in seismic signals includes determining presence of at least one seismic event in seismic signals corresponding to each of a plurality of seismic sensors. A correlation window is selected for each of the plurality of seismic signals. Each correlation window has a selected time interval including an arrival time of the at least one seismic event in each seismic signal. Each window is correlated to the respective seismic signal between a first selected time and a second selected time. Presence of at least one other seismic event in the seismic signals from a result of the correlating.

Abstract: An exhaust emission control system that provides on-board ammonia generation includes a valve disposed upstream of the LNT and SCR catalyst that operates to selectively control the flow of engine exhaust gas to an LNT and/or an SCR catalyst; while reformate fuel is being conveyed from a reformer to the LNT, the valve operates to cause the exhaust gas to bypass the LNT and flow directly to the SCR catalyst. The exhaust emission control system further includes a controller provided with an algorithm that monitors engine operating conditions and exhaust gas conditions, estimates the cumulative amount of exhaust gas created by the engine and the amount of NOx stored in the LNT, and calculates the amount of NOx required to be converted to NH3.

Abstract: Disclosed is a method for creating a gain function for seismic data and to processing methods for utilizing such a gain function. The method of creating the gain function generally includes representing the seismic data as a plot of the logarithm of amplitude versus time. Various order polynomial functions are subsequently fitted to the plotted seismic data. The best fitting polynomial is then selected from these various order polynomials, the inverse of which is the gain function. This gain function can be utilized in a seismic processing method.

Abstract: A method for removing non-geologic amplitude variations from seismic data. The method is based on the premise that lateral amplitude variations with spatial wavelengths shorter than the width of the Fresnel zone, a known wave propagation effect, for the target cannot be caused by changes in the reflectivity of the target and must, therefore, be due to non-geologic causes. The method permits these non-geologic amplitude effects to be identified and removed from the seismic data. The method may be implemented either manually or automatically by a computer.