A5011613668- Geophysical and Geoelectrical Methods
- Geophysical Methods and Applications
- Geological and Geophysical Studies
- Seismic Imaging and Inversion Techniques
- Seismic Waves and Analysis
- Underwater Acoustics Research
- Earthquake Detection and Analysis
- Methane Hydrates and Related Phenomena
- earthquake and tectonic studies
- Electromagnetic Simulation and Numerical Methods
- Scientific Research and Discoveries
- Geomagnetism and Paleomagnetism Studies
- Reservoir Engineering and Simulation Methods
- Advanced Numerical Methods in Computational Mathematics
- High-pressure geophysics and materials
- Geochemistry and Geologic Mapping
- Landslides and related hazards
- Geology and Paleoclimatology Research
- Cryospheric studies and observations
- Non-Destructive Testing Techniques
- Geological and Geochemical Analysis
- Geophysics and Gravity Measurements
- NMR spectroscopy and applications
- Seismology and Earthquake Studies
- Electromagnetic Scattering and Analysis
Lamont-Doherty Earth Observatory
2017-2025
Columbia University
2017-2025
BlueGreen Geophysics (United States)
2024
ORCID
2021
Scripps Institution of Oceanography
2009-2018
University of California, San Diego
2007-2017
Chevron (United States)
2012-2015
Institute of Oceanography
2005-2015
Applied GeoSolutions (United States)
2015
Portland State University
2015
Numerical methods for 1D forward modeling and inversion of marine controlled-source electromagnetic (CSEM) data are used to examine the inherent resolution various acquisition configurations thin resistive layers simulating offshore hydrocarbon reservoirs. Synthetic studies indicate that jointly inverting frequencies 0.1 [Formula: see text] offers better than either frequency alone. Further increasing bandwidth or density does not produce a commensurate increase in resolution. An inline...
This work presents MARE2DEM, a freely available code for 2-D anisotropic inversion of magnetotelluric (MT) data and frequency-domain controlled-source electromagnetic (CSEM) from onshore offshore surveys. MARE2DEM parametrizes the inverse model using grid arbitrarily shaped polygons, where unstructured triangular or quadrilateral grids are typically used due to their ease construction. Unstructured provide significantly more geometric flexibility parameter efficiency than structured...
We present a parallel goal-oriented adaptive finite element method that can be used to rapidly compute highly accurate solutions for 2.5-D controlled-source electromagnetic (CSEM) and 2-D magnetotelluric (MT) modelling problems. employ unstructured triangular grids permit efficient discretization of complex domains such as those containing topography, dipping layers multiple scale structures. Iterative mesh refinement is guided by error estimator considers the relative in strike aligned...
In Part 1 of this work, we develop an adaptive finite-element algorithm for forward modeling the frequency-domain, marine controlled-source electromagnetic (CSEM) response a 2D conductivity structure that is excited by horizontal electric dipole source. After transforming governing equations secondary fields into wavenumber domain, coupled system two partial differential strike-parallel and magnetic approximated using method. The model domain discretized unstructured triangular element grid...
Monitoring changes in hydrocarbon reservoir geometry and pore-fluid properties that occur during production is a critical part of estimating extraction efficiency quantifying remaining reserves. We examine the applicability marine controlled-source electromagnetic (CSEM) method to reservoir-monitoring problem by analyzing representative 2D models. These studies show CSEM responses exhibit small but measureable are characteristic reservoir-depletion geometry, with lateral flooding producing...
The fast Hankel transform (FHT) implemented with digital filters has been the algorithm of choice in EM geophysics for a few decades. However, other disciplines have predominantly relied on methods that break up integral into sum partial integrals are each evaluated quadrature. convergence sums is then accelerated through nonlinear sequence transformation. While such method was proposed nearly three decades ago, it demonstrated to be much slower than FHT. This work revisits this problem by...
Abstract The portion of the Central American margin that encompasses Nicaragua is considered to represent an end‐member system where multiple lines evidence point a substantial flux subducted fluids. seafloor spreading fabric incoming Cocos plate oriented parallel trench such flexural bending at outer rise optimally reactivates dense network normal faults extend several kilometers into upper mantle. Bending are thought provide fluid pathways lead serpentinization While geophysical anomalies...
Abstract Low-salinity submarine groundwater contained within continental shelves is a global phenomenon. Mechanisms for emplacing offshore include glacial processes that drove water into exposed during sea-level low stands and active connections to onshore hydrologic systems. While low-salinity thought be abundant, its distribution volume worldwide poorly understood due the limited number of observations. Here we image laterally continuous aquifers extending 90 km New Jersey Martha’s...
Antarctica's fast-flowing ice streams drain the sheet, with their velocity modulated by subglacial water systems. Current knowledge of these systems is limited to shallow portions near ice-bed interface, but hypothesized deeper groundwater could also influence streaming. Here, we use magnetotelluric and passive seismic data from Whillans Ice Stream, West Antarctica, provide first observations deep sub-ice stream groundwater. Our reveal a volume within >1-kilometer-thick sedimentary basin...
Submarine gas hydrate is a hazard to drilling, potential hydrocarbon resource, and has been implicated as factor in both submarine slope stability climate change. Bulk situ electrical resistivities evaluated from electromagnetic surveys have the provide an estimate of total volume fraction more directly than by using seismic well log data. We conducted marine controlled‐source sounding at Hydrate Ridge, Oregon, USA, August, 2004. Electromagnetic fields transmitted deep‐towed horizontal...
Existing numerical modeling techniques commonly used for electromagnetic (EM) exploration are bound by the limitations of approximating complex structures using a rectangular grid. A more flexible tool is adaptive finite-element (FE) method unstructured grids. Composed irregular triangles, an grid can readily conform to complicated structural boundaries. To ensure accuracy, refinement posteriori error estimator performed iteratively refine where solution accuracy insufficient. Two recently...
In the marine controlled-source electromagnetic method, Earth response varies in frequency; therefore, using a wide range of frequencies may better constrain geological structure than single frequency or only few closely spaced frequencies. Binary waveforms, such as square wave, provide number frequencies, though many are limited usefulness because rapid decline amplitude with frequency. waveform design can be improved by recognizing that class doubly symmetric waveforms has special...
The posterior distribution of earth models that fit observed geophysical data convey information on the uncertainty with which they are resolved. From another perspective, non-uniqueness inherent in most inverse problems interest can be quantified by examining model converged upon a Bayesian inversion. In this work we apply reversible jump Markov chain Monte Carlo method to sample for anisotropic 1-D seafloor conductivity constrained marine controlled source electromagnetic data. Unlike...
We describe the planning, processing, and uncertainty analysis for a marine CSEM survey of Scarborough gas field off northwest coast Australia, consisting 20 transmitter tow lines 144 deployments positioned along dense 2D profile complex 3D grid. The purpose this was to collect high-quality data set over known hydrocarbon prospect use it further development as mapping tool. Recent improvements in navigation processing techniques yielded frequency domain data. Data pseudosections exhibit...
Abstract First reported in the 1960s, offshore freshened groundwater (OFG) has now been documented most continental margins around world. In this review we compile a database documenting OFG occurrences and analyze it to establish general characteristics controlling factors. We also assess methods used map characterize OFG, identify major knowledge gaps, propose strategies address them. global volume of 1 × 10 6 km 3 ; predominantly occurs within 55 coast down water depth 100 m. is mainly...
Conventional regularized nonlinear inversion methods for estimating electrical conductivity from observed electromagnetic data seek to find a single model that fits the while minimizing user-imposed regularization norm. By contrast, Bayesian sampling techniques produce large suite of models, all which fit adequately, providing wealth statistical information about parameters. Importantly, this includes quantitative uncertainty estimates as well any property interest. In work, we apply...
SUMMARY Joint inversion of multiple electromagnetic data sets, such as controlled source and magnetotelluric data, has the potential to significantly reduce uncertainty in inverted electrical resistivity when two sets contain complementary information about subsurface. However, evaluating quantitatively model reduction is made difficult by fact that conventional methods—using gradients regularization—typically produce just one model, with no associated estimate parameter uncertainty....
Bayesian methods can quantify the model uncertainty that is inherent in inversion of highly nonlinear geophysical problems. In this approach, a likelihood function based on knowledge data noise statistics used to sample posterior distribution, which conveys information resolvability parameters. Because these distributions are multidimensional and nonlinear, we Markov chain Monte Carlo for efficient sampling. single become stuck local probability mode, run various randomized chains...