Vedran Lekic

Vedran Lekic
University of Maryland, College Park | UMD, UMCP, University of Maryland College Park · Department of Geology

PhD

About

78
Publications
6,241
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2,455
Citations
Citations since 2017
20 Research Items
1606 Citations
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2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300

Publications

Publications (78)
Article
Full-text available
The Seismic Experiment for Interior Structure (SEIS) of the InSight mission to Mars has been providing direct information on Martian interior structure and dynamics of that planet since it landed. Compared with seismic recordings on the Earth, ground-motion measurements acquired by SEIS on Mars are not only made under dramatically different ambient...
Article
Full-text available
Tidal interactions between planets or stars and the bodies that orbit them dissipate energy in their interiors. The dissipated energy heats the interior and a fraction of that energy will be released as seismic energy. Here we formalize a model to describe the tidally-driven seismic activity on planetary bodies based on tidal dissipation. To constr...
Article
Full-text available
Temperature distribution at depth is of key importance for characterizing the crust, defining its mechanical behavior and deformation. Temperature can be retrieved by heat flow measurements in boreholes that are sparse, shallow, and have limited reliability, especially in active and recently active areas. Laboratory data and thermodynamic modeling...
Article
Full-text available
Low-velocity layers within the crust can indicate the presence of melt and lithologic differences with implications for crustal composition and formation. Seismic wave conversions and reverberations across the base of the crust or intracrustal discontinuities, analysed using the receiver function method, can be used to constrain crustal layering. T...
Conference Paper
The Mw 4.2 Dover, DE, earthquake in 2017 represented an opportunity to evaluate seismicity in a passive margin setting, motivating a rapid deployment of instruments in order to record aftershocks. Within 24 hours of the main shock, personnel from the Lamont-Doherty Earth Observatory, the Department of Terrestrial Magnetism of the Carnegie Instituti...
Poster
On November 30, 2017, a magnitude 4.2 earthquake occurred just outside the city of Dover, DE, and was felt as far as Washington, DC, Philadelphia, PA, and New York, NY. Within 24 hours, seismologists from the University of Maryland, Carnegie Institution for Science, Lamont-Doherty Earth Observatory, Lehigh University, and the U.S. Geological Survey...
Preprint
Full-text available
Tidal interactions between planets or stars and the bodies that orbit them dissipate energy in their interiors. The energy dissipated drives internal heating and a fraction of that energy will be released as seismic energy. Here we formalize a model to describe the tidally-driven seismic activity on planetary bodies based on tidal dissipation.
Article
Full-text available
Inversion of surface wave data for crustal and upper-mantle structure is a staple of passive seismology, particularly since the advent of techniques enabling surface wave dispersion (SWD) and Rayleigh wave ellipticity measurements from ambient noise. Recent development and application of transdimensional Bayesian (TB) seismic inversion offers an ap...
Article
Full-text available
The InSight lander will deliver geophysical instruments to Mars in 2018, including seismometers installed directly on the surface (Seismic Experiment for Interior Structure, SEIS). Routine operations will be split into two services, the Mars Structure Service (MSS) and Marsquake Service (MQS), which will be responsible, respectively, for defining t...
Article
Full-text available
We present a new approach for evaluating existing crustal models using ambient noise datasets and its associated uncertainties. We use a transdimensional hierarchical Bayesian inversion (THBI) approach to invert ambient noise surface wave phase dispersion maps for Love and Rayleigh waves using measurements obtained from Ekstrom (2014). Spatiospectr...
Article
Full-text available
New tungsten isotope data for modern ocean island basalts (OIB) from Hawaii, Samoa, and Iceland reveal variable 182W/184W, ranging from that of the ambient upper mantle to ratios as much as 18 parts per million lower. The tungsten isotopic data negatively correlate with 3He/4He. These data indicate that each OIB system accesses domains within Earth...
Article
High-resolution models of seismic velocity variations constructed using body-wave tomography inform the study of the origin, fate, and thermochemical state of mantle domains. In order to reliably relate these variations to material properties including temperature, composition, and volatile content, we must accurately retrieve both the patterns and...
Article
Full-text available
Large low shear velocity provinces (LLSVPs), whose origin and dynamic implication remain enigmatic, dominate the lowermost mantle. For decades, seismologists have created increasingly detailed pictures of the LLSVPs through tomographic models constructed with different modeling methodologies, data sets, parametrizations and regularizations. Here, w...
Article
The large low shear-wave velocity provinces (LLSVP) are thermochemical anomalies in the deep Earth's mantle, thousands of km wide and ∼1,800 km high. This study explores the hypothesis that the LLSVPs are compositionally subdivided into two domains: a primordial bottom domain near the core-mantle boundary and a basaltic shallow domain extending fro...
Article
Large low shear velocity provinces (LLSVPs), whose origin and dynamic implication remain enigmatic, dominate the lowermost mantle. For decades, seismologists have created increasingly detailed pictures of the LLSVPs through tomographic models constructed with different modeling methodologies, data sets, parameterizations, and regularizations. Here,...
Article
Due to its complex history of deformation, the California Continental Borderland provides an interesting geological setting for studying how the oceanic and continental lithosphere responds to deformation. We map variations in present-day lithospheric structure across the region using Ps and Sp receiver functions at permanent stations of the Southe...
Article
Full-text available
Measurement of the differential rotation of the Sun's interior is one of the great achievements of helioseismology, providing important constraints for stellar physics. The technique relies on observing and analyzing rotationally-induced splittings of p-modes in the star. Here we demonstrate the first use of the technique in a laboratory setting. W...
Article
To explore how lithospheric structure varies between tectonic and magmatic terranes of the western United States, we use observations of shear-to-compressional wave conversions across lithospheric velocity interfaces. With a newly developed automatic method designed to take advantage of the EarthScope Transportable Array and other broadband seismic...
Article
This study explores the properties of the lithosphere-asthenosphere boundary (LAB) and other shallow mantle discontinuities across the diverse geologic provinces of the northwest United States. Sp phases were used to image three-dimensional discontinuity structure by common conversion point stacking with data from 804 temporary and permanent broadb...
Article
Full-text available
We present the current status of geo-neutrino measurements and their implications for radiogenic heating in the mantle. Earth models predict different levels of radiogenic heating and, therefore, different geo-neutrino fluxes from the mantle. Seismic tomography reveals features in the deep mantle possibly correlated with radiogenic heating and caus...
Article
Teleseismic waves can convert from shear to compressional (Sp) or compressional to shear (Ps) across impedance contrasts in the subsurface. Deconvolving the parent waveforms (P for Ps or S for Sp) from the daughter waveforms (S for Ps or P for Sp) generates receiver functions which can be used to analyse velocity structure beneath the receiver. Tho...
Article
Seismic images of the base of the lithosphere across the San Andreas fault system (California, USA) yield new constraints on the distribution of deformation in the deep lithosphere beneath this strike-slip plate boundary. We show that conversions of shear to compressional waves (Sp) across the base of the lithosphere are systematically weaker on th...
Article
Understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists. Using full-waveform seismic tomography, we imaged a pattern of horizontally elongated bands of low shear velocity, most prominent between 200 and 350 kilometers depth, which extends below the well-develope...
Article
Knowledge of the amount and distribution of radiogenic heating in the mantle is crucial for understanding the dynamics of the Earth, including its thermal evolution, the style and planform of mantle convection, and the energetics of the core. Although the flux of heat from the surface of the planet is robustly estimated, the contributions of radiog...
Article
Earth's lower mantle is dominated by a pair of antipodal large low shear velocity provinces (LLSVPs) that reach >1000 km up from the core–mantle boundary (CMB). These are separated by a ring of faster-than-average velocities thought to be related to subduction of oceanic lithosphere. How robustly does global tomography constrain velocity structure...
Article
Over the past three decades, advances in theory and improved quality and coverage of global seismic data have lead to progressively higher-resolution global images of earth structure. While long-wavelength velocity structure correlates well across recent global models, notable differences remain - particularly in the amplitudes and gradients of vel...
Article
The Late Paleozoic Alleghanian orogeny in the southern Appalachians was a result of the continental collision between Laurentia and Gondwana. The proposed suture zone between Laurentian Grenville basement and the Gondwana-affiliated Suwanee terrane is marked by south-dipping reflections in COCORP profiles, the Brunswick Magnetic anomaly (BMA), and...
Article
Upper mantle and crustal velocity interfaces, such as those corresponding to the base of the crust and the base of the lithosphere, produce detectable conversions of seismic energy that can be analyzed using a receiver function approach. Unlike compressional-to-shear (Ps) receiver functions, in which signals from mantle discontinuities are often ov...
Article
As revealed by seismic tomography, the strength of lateral heterogeneity increases abruptly near the base of the mantle, marking the thermal and compositional boundary layer at the core-mantle boundary (CMB). Many intriguing features are observed in D": significant anisotropy, ultra-low velocity zones, and a velocity discontinuity at the top of D"...
Article
Comparison of five S-velocity 3-D models reveals strikingly similar spectral character within five distinct regions in the mantle; three of them have large amplitudes (heterosphere, transition zone and abyssal layer) and are separated by two buffer zones of lower power and whiter spectrum (Dziewonski et al., 2010). There are planetary scale correla...
Conference Paper
The Berkeley North American regional azimuthal anisotropy model reveals the presence of three anisotropic layers throughout the stable part of the North American cratonic upper mantle (Yuan and Romanowicz, 2010). While in the bottom asthenospheric layer the fast axis direction is parallel to the current plate motion direction, the top two lithosphe...
Article
The stretching and break-up of tectonic plates by rifting control the evolution of continents and oceans, but the processes by which lithosphere deforms and accommodates strain during rifting remain enigmatic. Using scattering of teleseismic shear waves beneath rifted zones and adjacent areas in Southern California, we resolve the lithosphere-asthe...
Article
Global mantle tomography can be improved through better use of data and application of more accurate wave propagation methods. However, few techniques have been developed for objective validation and exploration of the resulting tomographic models. We show that cluster analysis can be used to validate and explore the salient features across such mo...
Article
Mapping the elastic and anelastic structure of the Earth's mantle is crucial for understanding the temperature, composition and dynamics of our planet. In the past quarter century, global tomography based on ray theory and first-order perturbation methods has imaged long-wavelength elastic velocity heterogeneities of the Earth's mantle. However, th...
Article
Full-text available
Accurately inferring the radially anisotropic structure of the mantle using seismic waveforms requires correcting for the effects of crustal structure on waveforms. Recent studies have quantified the importance of accurate crustal corrections when mapping upper mantle structure using surface waves and overtones. Here, we explore the effects of crus...
Article
As global waveform-modeling schemes rooted in perturbation theory are supplanted by fully numerical alternatives, such as the Spectral Element Method (e.g. SEM: Komatitsch and Tromp, 2002), the improved wavefield accuracy for complex 3D structures also carries increased computational cost. Lekic and Romanowicz (2010) inverted waveforms of fundament...
Article
Lateral variations in lower mantle shear attenuation can be inferred from differential t* measurements between the ScS and S seismic phases, deltaScS-St*. A classical approach for measuring differential t* utilizes spectral ratios. In this study, a different method, based on instantaneous frequency matching is used to calculate the deltaScS-St*. Th...
Article
Mineralogical interpretations of seismic velocity and density profiles can help constrain the composition of the Earth's mantle. Using 1-D seismic models limits the validity of these interpretations as they assume that lateral variations of mantle composition are not significant; yet, this assumption runs contrary to predictions based both on caref...
Article
The primary goals of this work are to better understand the origin of the rheological differences between the lithosphere and asthenosphere and to improve constraints on mantle structure internal to the lithosphere. We have used Sp receiver functions at over 130 seismic stations to image mantle discontinuities beneath North America and Australia. I...
Article
The Gulf of California, a young (12-15 Ma) oblique rift system, exhibits large variations in magmatism, rift width, and sedimentary cover, making it an ideal setting for studying the mechanisms and processes that control rifting. Characterizing lithospheric thickness variations in this region is crucial for understanding the interdependency of exte...
Article
Close examination of the long wavelength shear velocity signal in the lowermost mantle in the wavenumber domain ties several geophysical observations together and leads to fundamental inferences. When mantle shear velocity model S362ANI at a depth of 2800km is expanded in spherical harmonics up to degree 18, more than one half of the seismic model'...
Article
Accurate accounting for the effects of crustal structure on long-period seismic surface waves and overtones is difficult but indispensable for determining elastic structure in the mantle. While standard linear crustal corrections (SLC) have been shown to be inadequate on the global scale, newer non-linear correction (NLC) techniques are computation...
Article
Surface waves and overtones provide excellent constraints on crustal, upper mantle, and transition zone structure. They offer far better radial resolution of shallow structure than is possible with teleseismic body waves, while simultaneously having excellent global coverage and signal-to-noise ratios. Indeed, since its development a quarter centur...
Article
We present a new global radially anisotropic S velocity model of the mantle derived from a dataset of 3 component broadband waveforms of surface and body waves. The model is derived from the same dataset as a previous model (Panning and Romanowicz, 2006), but takes advantage of a new approach for modeling the non-linear effects of crustal structure...
Article
Anomalies of shear velocities in the lowermost mantle, representing either thermal or compositional heterogeneity (or both), are dominated by a “recumbent” P20 spherical harmonic: a P20 with its axis of symmetry rotated to the equatorial plane. It is characterized by two antipodally opposed regions of low velocities, separated by a circum-polar rin...
Article
Constraining the frequency dependence of intrinsic seismic attenuation in the Earth is crucial for: 1. correcting for velocity dispersion due to attenuation; 2. constructing attenuation and velocity models of the interior using datasets with different frequency contents; and, 3. interpreting lateral variations of velocity and attenuation in terms o...
Article
Mapping the elastic and anelastic structure of the Earth's mantle is crucial for understanding the temperature, composition and dynamics of our planet. Extracting the information contained in seismic waveforms is the key to constraining the elastic and anelastic structure within the Earth, and is the goal of our work. In the past quarter century, g...
Article
The 2008 Cooperative Institute for Deep Earth Research (CIDER) program facilitated collaboration between researchers from seismology, geodynamics, mineral physics, and geochemistry to study, model and better understand the interior of the Earth. Through this multidisciplinary approach, we have developed a self- consistent paradigm of mantle structu...
Article
Improving the resolution of global upper mantle tomographic models of shear wavespeed and anisotropy is crucial for understanding the nature and morphology of upper mantle heterogeneities. Traditional methods of global tomography that rely on infinite-frequency and first-order perturbation theory become increasingly inadequate as shorter-wavelength...
Article
As the frequency band typically considered in global S wave tomography of the earth's mantle does not allow the resolution of crustal structure, but the effect on seismic waves of strong heterogeneity in the crust cannot be neglected, a standard approach has long been to perform approximate crustal corrections, based on normal mode perturbation the...
Article
Constraining the frequency-dependence of intrinsic seismic attenuation in the Earth is crucial for: 1. correcting for velocity dispersion due to attenuation; 2. constructing attenuation and velocity models of the interior using datasets with different frequency contents; and, 3. interpreting lateral variations of velocity and attenuation in terms o...
Article
Most of the tomographic models employ data sets that had satisfactory resolution in a limited radial extent. For example, studies using teleseismic travel times do not have resolution in the upper mantle, even though using matrix conditioning methods it is possible to derive a "model" of the upper mantle. Similarly, some studies using surface waves...
Article
In the past quarter century, global tomography based on ray theory and first-order perturbation methods has imaged long-wavelength velocity heterogeneities of the Earth's mantle. While these models have contributed significantly to our understanding of mantle circulation, the development of higher resolution images of the Earth's interior holds tre...
Article
Full-text available
1] Previous studies have documented the potential for using relatively short-period body waves and intermediate-period surface waves to explore the structure and tectonics of Europa. We show that long-period measurements (0.001 to 0.1 Hz) may have large amplitudes of displacement (millimeters to centimeters) and are potentially measurable from orbi...
Article
Full-text available
In order to examine the potential of seismology to determine the interior structure and properties of Europa, it is essential to calculate seismic velocities and attenuation for the range of plausible interiors. We calculate a range of models for the physical structure of Europa, as constrained by the satellite's composition, mass, and moment of in...
Article
Over the past decade, seismic tomography has revealed that subducting lithospheric slabs interact with the transition zone in a variety of ways, directly penetrating into the lower mantle in some locations, while stagnating in others. Here, we present preliminary results of attempts to characterize and quantify the stagnation of slab material in th...
Article
Some large uncertainties still exist in global average attenuation measurements at long periods (150-300 s), limiting their usefulness for constraining the depth dependence of Q in the mantle. A 15-20 % discrepancy between measurements of Rayleigh wave attenuation using traveling and standing waves has been confirmed by many different studies. Ther...
Article
Mapping 3D variations of intrinsic seismic attenuation within the mantle is crucial for determining the physical cause of observed mantle heterogeneity. While long-wavelength models of upper mantle 3D anelastic structure do exist, obtaining higher-resolution models requires correcting for purely elastic effects of scattering and (de)focusing which...
Article
Three dimensional Earth models (Ritsema et al., 2004; Panning and Romanowicz, 2006; Kustowski et al., 2006) derived using data that have good control on the structure in the transition zone (body-wave waveforms or overtone measurements) all show a discontinuous or very rapid change in the spectrum of lateral heterogeneity at the boundary between th...
Article
Understanding the distribution of seismic attenuation in the mantle is important for discriminating between chemical and thermal heterogeneity as well as interpreting models of elastic structure derived from data at different frequencies. While mapping of the 3D elastic structure of the upper mantle has benefited from approximate first-order pertur...
Article
Measurements of the seismic response of Europa remotely from an orbiter or using a lander can greatly expand our knowledge of the internal structure and thermal evolution and therefore of the potential for life. We explore a range of reasonable physical models of Europan 1D structure to determine the types of seismic signals relevant for discrimina...
Article
Full-text available
Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 110 (2005): B09101, doi:10.1029/2004JB003473. We gathered seismic refraction and wide-angle reflection data from...
Article
Subducting oceanic lithosphere is the main driving force of plate tectonics and the main source of upper mantle chemical heterogeneity. Here we present a comprehensive characterization of all regions of deep seismicity (> 500 km): Japan, Izu-Bonin, Marianas, Philippines, Java, Solomon, New Hebrides, Tonga, and South America. Regional tomographic st...
Conference Paper
P-waves recorded during wide-angle refraction experiments provide a measure of crustal thickness and the velocity structure of the crust and uppermost mantle along the Mid-Atlantic Ridge near 35N. We use 29,605 crustal refractions, 14,682 reflections from the base of the crust, and 9322 mantle refractions to generate a three-dimensional anisotropic...
Conference Paper
P-waves recorded during wide-angle refraction experiments provide a measure of crustal thickness and the velocity structure of the crust and uppermost mantle along the Mid-Atlantic Ridge near 35N. We use 29,605 crustal refractions, 14,682 reflections from the base of the crust, and 9322 mantle refractions to generate a three-dimensional anisotropic...

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Projects (5)
Project
1. Build a new crustal models that includes uncertainties quantified using a Bayesian approach. 2.To what degree will this data set inform existing crustal models? or In which regions of data availability will new crustal models derived from this data set differ from previous versions, within data uncertainty? 3. "How will new data revise old assumptions on extrapolating a sparsely sampled Earth model based on tectonic analogy?
Project
Constrain the character of seismic attenuation in the mantle
Project
Improve images of upper mantle structure using full waveform tomography and accurate forward modeling schemes.