About

Colin A. Zelt is a professor in the Department of Earth, Environmental and Planetary Sciences at Rice University. His research areas include seismic modeling and inversion techniques, inverse theory, wide-angle seismic data acquisition, modeling, and interpretation. He conducts geophysical studies of the lithosphere, sedimentary basins, and shallow environments. Dr. Zelt holds a B.Sci. in Physics and Applied Math from the University of Victoria, obtained in 1984, and a Ph.D. in Geophysics from the University of British Columbia, earned in 1989. He is a member of several professional societies, including the American Geophysical Union, the Society of Exploration Geophysicists, and the Environmental and Engineering Geophysical Society.

Research topics

• Computer Science
• Geology
• Seismology
• Statistics
• Geodesy
• Mathematics
• Algorithm
• Geochemistry

Selected publications

• Seismic refraction methods

  2022-11-15 · 2 citations

  book-chapter1st authorCorresponding

  This method chapter comprises a short introduction to the use of refraction seismic methods. It describes the fundamental theory, planning considerations, opportunities, limitations, and resolution of the geophysical method and references relevant literature and related case histories. The section is written to enable the reader to decide whether this method fits the intended purpose and for a better understanding of the physics behind it.

  PublisherDOI

• Early arrival waveform inversion using data uncertainties and matching filters with application to near-surface seismic refraction data

  Geophysics · 2022 · 7 citations

  Senior authorCorresponding
  • Computer Science
  • Algorithm
  • Computer Science

  ABSTRACT We develop an early arrival waveform inversion (EAWI) technique for high-resolution near-surface velocity estimation by iteratively updating the P-wave velocity model to minimize the difference between the observed and calculated seismic refraction data. Traditional EAWI uses a least-squares penalty function and an acoustic forward-modeling engine. Conventional least-squares error is sensitive to data with low signal-to-noise ratio (S/N) and iterations of EAWI stop at a local-minimum data misfit or at the preassigned maximum number of iterations. These stopping criteria can result in overfitting the data. In addition, fitting the elastic field data with an acoustic modeling engine can introduce artifacts in velocity estimation, especially in land data with significant elastic effects. To overcome these challenges, we develop a robust EAWI (REAWI) method by (1) incorporating the data uncertainties into the penalty function and (2) mitigating the elastic effects using a matching filter workflow. The data uncertainties are estimated from waveform reciprocal errors. When full-waveform reciprocity is not available, trace interpolation is applied. The proposed method prevents closely fitting data with low S/N, avoids overall overfitting by stopping the iterations when a normalized chi-square (χ2) waveform misfit of one is achieved, and is less affected by elastic effects. Numerical examples and application to near-surface refraction data at a groundwater contamination site suggest that the final REAWI models are more accurate than the corresponding EAWI models, at the same level of misfit. This is the first known application of a matching filter workflow to real land data. The final REAWI models satisfy an appropriate misfit between the real data and predicted elastic P-wave data, making this approach in this respect equivalent to elastic waveform inversion. We also develop a method to analyze model constraint by examining the energy of the wavefield Fréchet derivative thereby avoiding the influence of the data residuals in traditional Fréchet kernels.

  PublisherDOI

• Sensitivity analysis of acoustic waveform inversion to velocity anomalies in the near-surface using the Fréchet derivative

  Second International Meeting for Applied Geoscience & Energy · 2022-08-15

  articleSenior author

  Seismic waveform inversion (WI) has been applied to high- resolution velocity model building at all scales, but how truthful are the amplitudes of velocity anomalies recovered in the WI models? Previous sensitivity analysis of WI has focused on estimating model uncertainties, understanding the radiation patterns of different geophysical parameters, and separating the tomography and migration mode of WI in the wavenumber-domain. Few of the studies explore if the WI is equally sensitivity to high and low velocity anomalies, whereas nonlinear traveltime tomography (TT) is known to be more sensitive to high velocity anomalies than low velocity anomalies because of wavefront healing. In this paper, we analyze the sensitivity of WI to velocity anomalies by first comparing the amplitudes of wavefield perturbations generated by injected high and low velocity anomalies. We provide theoretical calculations for a point scatter and numerical simulations for a velocity anomaly with a size equivalent to a fraction of the dominant wavelength. Then, we perform WI tests to recover high and low velocity anomalies of equal velocity or slowness perturbations. Acoustic waveform modeling and inversion are used for simplicity. The preliminary results show acoustic WI is potentially more sensitive to low velocity anomalies than high velocity anomalies. The joint inversion of traveltime and waveform data is advocated for near-surface velocity estimation, since the different sensitivity of TT and acoustic WI can be complementary to each other.

  PublisherDOI

• Crustal structure and tectonic implications of the southernmost Merida Andes, Venezuela, from wide-angle seismic data analysis

  Journal of South American Earth Sciences · 2022-05-25 · 4 citations

  article
  PublisherDOI

• Traveltime Tomography Using Controlled-Source Seismic Data

  Encyclopedia of earth sciences series/Encyclopedia of earth sciences · 2021-01-01 · 2 citations

  book-chapter1st authorCorresponding
  PublisherDOI

• Evolution of Archean Sanukitoids from the Otto Stock by Magma Mixing and Na–K Metasomatism: Evidence from Petrological Observations and Lithium Isotope Geochemistry

  Journal of Petrology · 2021 · 6 citations

  • Geology
  • Geochemistry

  Abstract Petrogenetic models for the genesis of Archean sanukitoids are diverse in the literature but most point to the initiation of plate tectonics and the construction of the first proto-continents during the Late Archean. These rocks include diorites, monzonites, monzodiorites, quartz monzodiorites, trachyandesites, granodiorites and tonalites, and are defined as having SiO2 = 55–60 wt%, Na2O + K2O = 6 wt%, MgO > 6 wt%, Mg# > 60, Ni–Cr > 100 ppm, Sr and Ba = 600–1800 ppm, chondrite-normalized Ce and Yb values of 80–250 and 4–10, respectively, and no Eu anomalies. Petrogenetic models include the partial melting of mantle peridotite previously metasomatized by fluids of crustal or mantle origin, partial melting of subducted slabs and assimilation of peridotite, and partial melting of undepleted peridotite with subsequent mixing with tonalite–trondhjemite–granodiorite (TTG) crustal partial melts and addition of carbonatite, all of which may or may not include subsequent differentiation by fractional crystallization. Here, extraordinary textural relations unequivocally show that at the Late Archean Otto stock, Abitibi, Canada, sanukitoids resulted from the assimilation of clinopyroxenite by monzonitic magmas and coeval magmatic–hydrothermal Na–K metasomatism. The metasomatized monzonites (± quartz), melanogranites, granodiorites, and sanukitoidal melanoporphyries were subsequently cut by swarms of lamprophyre dykes hosting a different set of hydrothermal alteration assemblages, including propylitic alteration, biotitization, chloritization, and pyritization, along with associated enrichments in Au. These alterations are shown to be associated with the nearby Cadillac–Larder Lake Fault Zone and the world-class Kirkland Lake gold deposit. The Li isotopic compositions of these rocks correlate with Au concentrations and range from magmatic values of ∼ +4 ‰ up to +10·4 ‰ in Na–K metasomatized and Au-depleted rocks, and from magmatic values of ∼4 ‰ down to 0·6 ‰ in rocks hosting propylitic, chloritic, and biotitic alteration and Au enrichments of up to 2·9 ppm Au.

  PublisherDOI

• Traveltime Tomography Using Controlled-Source Seismic Data

  Encyclopedia of earth sciences series/Encyclopedia of earth sciences · 2020-01-01 · 1 citations

  book-chapter1st authorCorresponding
  PublisherDOI

• Detecting an underground tunnel by applying joint traveltime and waveform inversion

  Journal of Applied Geophysics · 2020 · 16 citations

  • Computer Science
  • Geology
  • Seismology
  PublisherOA PDFDOI

• Upper Crustal Structure and Magmatism in Southwest Washington: <i>V</i>_<i>p</i>, <i>V</i>_<i>s</i>, and <i>V</i>_<i>p</i>/<i>V</i>_<i>s</i> Results From the iMUSH Active‐Source Seismic Experiment

  Journal of Geophysical Research Solid Earth · 2019-07-01 · 9 citations

  articleOpen access

  Abstract Structural details of the crust play an important role in controlling the distribution of volcanic activity in arc systems. In southwest Washington, several different regional structures associated with accretion and magmatism have been invoked to explain the broad distribution of Cascade volcanism in this region. In order to image these regional structures in the upper crust, Pg and Sg travel times from the imaging Magma Under St. Helens (iMUSH) active‐source seismic experiment are inverted for V p , V s , and V p / V s models in the region surrounding Mount St. Helens. Several features of these models provide new insights into the regional structure of the upper crust. A large section of the Southern Washington Cascades Conductor is imaged as a low V p / V s anomaly that is inferred to represent a broad sedimentary/metasedimentary sequence that composes the upper crust in this region. The accreted terrane Siletzia is imaged west of Mount St. Helens as north/south trending high V p and V p / V s bodies. The V p / V s model shows relatively high V p / V s regions near Mount St. Helens and the Indian Heaven Volcanic Field, which could be related to the presence of magmatic fluids. Separating these two volcanic regions below 6‐km depth is a northeast trending series of high V p and V s bodies. These bodies have the same orientation as several volcanic/magmatic features at the surface, including Mount St. Helens and Mount Rainier, and it is argued that these high‐velocity features are a regional‐scale group of intrusive bodies associated with a crustal weak zone that focuses magma ascent.

  PublisherOA PDFDOI

• Lithospheric Structure of Northwestern Venezuela From Wide‐Angle Seismic Data: Implications for the Understanding of Continental Margin Evolution

  Journal of Geophysical Research Solid Earth · 2019-11-07 · 16 citations

  article

  Abstract Northwestern Venezuela is located in the complex deformation zone between the Caribbean and South American plates. Several models regarding the lithospheric structure of the Mérida Andes have been proposed. Nevertheless, they lack relevant structural information in order to support the interpretation of deeper structures. Therefore, a 560‐km‐long refraction profile across the northern part of Mérida Andes, oriented in a NNW direction, covering areas from the Proterozoic basement in the south, to both Paleozoic and Meso‐Cenozoic terranes of northwestern Venezuela to the north, is analyzed in this contribution. Thirteen land shots were recorded by 545 short‐deployment seismometers, constraining P wave velocity models from first‐arrival seismic tomography and layer‐based inversion covering the whole crust in detail, with some hints to upper mantle structures. The most prominent features imaged are absence of a crustal root associated to the Mérida Andes, as the Northern Andes profile is located marginal to the Andean crustal domain, and low‐angle subduction of the Caribbean oceanic slab (~10–20°) beneath northwestern South America. Further crustal structures identified in the profile are (a) crustal thinning beneath the Falcón Basin along the western extension of the Oca‐Ancón fault system interpreted as a back‐arc basin; (b) suture zones between both the Proterozoic and Paleozoic provinces (Ouachita‐Marathon‐related suture?), and Paleozoic and Meso‐Cenozoic terranes (peri‐Caribbean suture) interpreted from lateral changes in seismic velocity; and (c) evidence of a deep Paleozoic(?) extensional basin, underlying thick Mesozoic and Cenozoic sequences (beneath the Guárico area).

  PublisherDOI

Recent grants

• Development of frequency-dependent traveltime tomography for controlled-source seismic data.

  NSF · $227k · 2012–2017

Frequent coauthors

• A. Levander

  Rice University

  80 shared

• Priyank Jaiswal

  26 shared

• M. B. Magnani

  Southern Methodist University

  22 shared

• Fuchun Gao

  TGS (Norway)

  22 shared

• Jianxiong Chen

  Fuzhou University

  14 shared

• Stephen A. Clark

  Equinor (United Kingdom)

  12 shared

• G. Fradelizio

  Chevron (Canada)

  11 shared

• Dale S. Sawyer

  10 shared