Abstract: A device for assigning to the unknown onset of a signal in a noisy time series a probability of that onset having a signed excursion away from the trace mean including one or more means arranged to: define a polarity at a given time sample by reference to the sign of the amplitude difference between the extrema immediately before and after the given time sample in the time series; define a positive and a negative polarity probability density function; take the respective products of the positive and negative polarity probability density functions with an onset probability density function defining the probability that the onset of the signal occurs at a given time sample; and marginalize the respective products of the positive and negative polarity probability density functions with the onset probability density function over time to estimate final probabilities that the onset has a positive or a negative polarity.

Abstract: A method for using microseismic data during an injection or perforation event includes injecting fluid or perforating a well to create cracks in the formation. Microseismic data is obtained from the formation and forward modelling source parameter estimations are performed using a full moment tensor space source model and a double-couple source model. Likelihoods of the microseismic data are calculated for each model type by forward modelling synthetic data from a sampled source parameter probability distribution derived from each estimation, and by comparing the synthetic data with the microseismic data. The likelihoods are marginalized over prior probabilities for the source models, and Bayesian inference converts the likelihoods and prior probabilities to posterior probabilities. The posterior probabilities for the full tensor space and double-couple source models are compared to reveal whether an event is a fracture opening, fracture closing, or a slip on a fault plane.

Abstract: A device for assigning to the unknown onset of a signal in a noisy time series a probability of that onset having a signed excursion away from the trace mean including one or more means arranged to: define a polarity at a given time sample by reference to the sign of the amplitude difference between the extrema immediately before and after the given time sample in the time series; define a positive and a negative polarity probability density function; take the respective products of the positive and negative polarity probability density functions with an onset probability density function defining the probability that the onset of the signal occurs at a given time sample; and marginalize the respective products of the positive and negative polarity probability density functions with the onset probability density function over time to estimate final probabilities that the onset has a positive or a negative polarity.

Abstract: A method is provided for processing microseismic data whereby the relative probability of an earthquake source model type, or combination of source model types, is estimated by: performing forward modelling source parameter estimation on the microseismic data, the estimation being constrained to one or more selected source model types; calculating the likelihoods of the microseismic data for given source model types by forward-modelling synthetic data from a sampled source parameter probability distribution derived from the estimation for each given source model type, and comparing the synthetic data against the microseismic data; marginalizing the calculated data likelihoods over prior probabilities for the model parameters for the given source model types to give respective likelihoods for the given source model types; and using Bayesian inference to convert the source model type likelihoods and the prior probabilities to posterior probabilities for the source model types.

Abstract: A marine cable for seismic surveys is described with a plurality of ceramic pressure sensors arranged in groups of at least two pressure sensors with a group output being representative of the vertical pressure gradient at the group location, and an inclinometric system including one or more transducers for determining the orientation of the sensors of the group in order to determine their true vertical separation.

Abstract: A marine cable for seismic surveys is described with a plurality of ceramic pressure sensors (901-904) arranged in groups of at least two pressure sensors with a group output being representative of the vertical pressure gradient at the group location, and an inclinometric system including one or more transducers for determining the orientation of the sensors of the group in order to determine their true vertical separation.

Abstract: A marine cable for seismic surveys is described with a plurality of ceramic pressure sensors arranged in groups of at least two pressure sensors with a group output being representative of the vertical pressure gradient at the group location, and an inclinometric system including one or more transducers for determining the orientation of the sensors of the group in order to determine their true vertical separation.

Abstract: A marine cable for seismic surveys is described with a plurality of ceramic pressure sensors (901-904) arranged in groups of at least two pressure sensors with a group output being representative of the vertical pressure gradient at the group location, and an inclinometric system including one or more transducers for determining the orientation of the sensors of the group in order to determine their true vertical separation.

Abstract: Methods and apparatus are described for the seismic exploration of strata adjacent to a borehole, wherein an arrangement of geophones is lowered into the borehole and clamped to the wall. The geophones are clamped at essentially equal angular distances along the circumference of the borehole. A plurality of such arrangements can be positioned along the longitudinal axis of the borehole. By combining the outputs of the geophones noise signals generated by symmetric guided waves are attenuated. The arrangement can be used for cross-well seismic acquisition and in combination with seismic sources and/or attenuator so as to form an single-unit exploration tool for borehole seismics.