Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for determining a velocity model for a geological region. In one aspect, a method comprises: obtaining a current velocity model for the geological region; obtaining pre-stack and post-stack seismic data characterizing the geological region; and for each of a plurality of iterations: identifying a plurality of reflection events from the post-stack seismic data and the current velocity model; determining a respective observed travel time for each of the plurality of reflection events, comprising, for each reflection event, determining the respective observed travel time for the reflection event based at least in part on kinematic features derived from a respective seismic trace included in the pre-stack seismic data; and updating the current velocity model based at least in part on the observed travel times of the plurality of reflection events.

A method for borehole measurements may comprise receiving one or more signals from a linear receiver array, computing an arctan of a Hilbert Transform, isolating a first arriving energy, selecting a reference instantaneous phase on a reference receiver, finding the reference instantaneous phase for the linear receiver array, computing a relative travel time shift, combining a reference pick time with a relative time, and determining a travel time. A system for borehole measurements comprise a conveyance, a bottom hole assembly attached to the conveyance, a linear receiver array, wherein the linear receiver array is disposed on the bottom hole assembly, and a computer system connected to the linear receiver array.

A method of predicting parameters of an earthquake uses an array of ionosondes to scan an observed volume of an ionosphere located above a seismically active zone. The method includes monitoring ionograms provided by the array of ionosondes; detecting the presence of at least one seismic-induced irregularity (SII); determining a first predicted parameter corresponding to an epicenter location; and determining one or more predicted parameters selected from a group consisting of a magnitude, a time of occurrence, and a hypocenter depth. Algorithms for calculating the predicted parameters are presented in detail.

A seismic data analysis system includes seismic receivers to collect seismic survey data, wherein the seismic survey data includes direct and reflected arrival data in response to at least one seismic source fired at different shot offsets. The system also includes memory that stores the collected seismic survey data. The system also includes a processing unit that extracts traveltimes for direct and reflected arrivals from the seismic survey data and performs an inversion using the direct and reflected arrival traveltimes simultaneously to determine anisotropy parameters, including Thomsen parameters, epsilon () and delta (), for at least one layer of a vertical transversely isotropic (VTI) model.

A method for analyzing acoustic/elastic waves to determine subsurface structure of the earth includes receiving a plurality of observations of a seismic acoustic/elastic wave-field from a plurality of sensors; generating a plurality of Bernstein grids of differing resolutions; calculating a data misfit of the plurality of observations with respect to an initial subsurface structure model defined in terms of conic combinations of Bernstein polynomials on a lowest resolution Bernstein grid, and mapping the data misfit from the Bernstein grid onto a Lagrangian grid; updating the subsurface structure model by minimizing the data misfit between the plurality of observations and observations obtained by a simulation; increasing resolution of the Bernstein grid and recomputing the updated subsurface structure model on the increased resolution Bernstein grid; and mapping the recomputed subsurface structure model onto the Lagrangian grid.

A system and method for modeling seismic data using time preserving tomography including storing an initial set of parameter values representing an initial seismic data model. The initial seismic model may correspond to at least two or more ray pairs. Each ray pair may have a traveltime. An altered model may be generated by altering two or more parameter values in the initial set of parameter values for each of two or more ray pairs in the initial model. Altering one parameter value without altering the remaining of the two or more parameter values may correspond to a change in the traveltime of each of the ray pairs, while altering the two or more parameter values in combination typically corresponds to no net change in the traveltime of each of the ray pairs.

Method and system for ongoing monitoring for underground structure at or near a production wellpad is provided. The system includes a sparse acquisition grid and utilizes information obtained from Rayleigh waves to monitor subsurface structures.

Survey design for data acquisition using marine non-impulsive sources can include operating a first marine non-impulsive source at over a first frequency range for a first sweep length and operating a second marine non-impulsive source over a second frequency range for a second sweep length. The first sweep length can be based on available geological information of a subsurface location that is a target of a marine seismic survey, an intended speed of a marine survey vessel, and the first frequency range. The second sweep length can be based on the available geological information, the intended speed, and the second frequency range.

The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems, for generating a velocity model for a subsurface structure. One computer-implemented method for determining velocity model for a subsurface structure includes generating, by at least one hardware processor, a first velocity model for the subsurface structure by performing a refraction traveltime tomography procedure based on an initial velocity model; and generating, by the at least one hardware processor, a first refined velocity model based on the first velocity model and a structure skeleton model, wherein the structure skeleton model is determined based on reflection seismic data of the subsurface structure.

Methods and devices for geophysical exploration include: acquiring seismic data representing a subterranean formation; obtaining a plurality of virtual super gathers (VSGs) comprising the seismic data by sorting the seismic data based on a hypercube with dimensions comprising common midpoint X-Y coordinates, an offset, and an azimuth, wherein one or more seismic attributes are obtained at the dimensions of the hypercube; transforming the seismic data, in the plurality of VSGs from a time-offset domain to a frequency-phase velocity domain; isolating, for VSGs of the plurality, frequencies and phase velocities of the frequency-phase velocity domain based on a windowing operation; and for frequencies isolated by the windowing operation, identifying a maximum magnitude of a phase velocity spectrum from the plurality of VSGs.