A5047556851- earthquake and tectonic studies
- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Seismic Waves and Analysis
- Seismic Imaging and Inversion Techniques
- Geological and Geophysical Studies
- Geophysics and Sensor Technology
- Geological formations and processes
- Geological Studies and Exploration
- Seismology and Earthquake Studies
- Geology and Paleoclimatology Research
- Methane Hydrates and Related Phenomena
- Hydrocarbon exploration and reservoir analysis
- Reservoir Engineering and Simulation Methods
- Geochemistry and Geologic Mapping
- Underwater Acoustics Research
- Earthquake Detection and Analysis
- Geological Formations and Processes Exploration
- Geomagnetism and Paleomagnetism Studies
- Geological and Tectonic Studies in Latin America
- Geophysical and Geoelectrical Methods
- Landslides and related hazards
- Geological Modeling and Analysis
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Hydraulic Fracturing and Reservoir Analysis
Northern Arizona University
2020-2025
Lamont-Doherty Earth Observatory
2013-2023
Columbia University
2013-2023
Southern Methodist University
2023
Massachusetts Institute of Technology
1994-2019
Carnegie Observatories
2019
Carnegie Institution for Science
2019
Georgia Institute of Technology
1999-2001
Long-period surface-wave (R(1), G(1)), body-wave (S, SS, SSS), and ScS-reverberation data have been inverted to obtain anisotropic structures along seismic corridors that sample Australia the western Pacific. These models support proposal Lehmann discontinuity beneath stable continents represents a transition from an lithosphere more isotropic material in lower part of continental tectosphere.
The seismic structure of the Tonga‐Hawaii corridor has been investigated by combining two data sets: Revenaugh and Jordan's reflectivity profile from S c reverberations, which provides travel times to impedance contrasts across major mantle discontinuities, 1500 new observations frequency‐dependent phase delays for three‐component , SS SSS body waves R 1 G surface waves, constrain velocity within this layered framework. shear turning in upper showed significant splitting SH SV components,...
We have developed a new method to retrieve seismic surface wave phase velocity using dense arrays. The measures variations between nearby stations based on waveform cross-correlation. coherence in waveforms adjacent results highly precise relative estimates. Frequency-dependent are then inverted for spatial apparent via the Eikonal equation. amplitudes measured individual used correct account multipathing Helmholtz By and other data selection criteria, we construct an automated system that...
Splitting measurements of teleseismic shear waves, such as SkS, have been used to estimate the amount and direction upper mantle anisotropy worldwide. These are usually made by approximating anisotropic regions a single homogeneous layer searching for an apparent fast (w) apparen splitting time (Dt ) minimizing energy on transverse component back projected seismogram. In this paper, we examine validity assumption. particular, use synthetic seismograms explore how vertically varying medium...
As the Pacific–Farallon spreading center approached North America, Farallon plate fragmented into a number of small plates. Some microplate fragments ceased subducting before reached trench. Most tectonic models have assumed that oceanic slab detached from these microplates close to trench, but recent seismic tomography studies revealed high-velocity anomaly beneath Baja California appears be fossil still attached Guadalupe and Magdalena microplates. Here, using surface wave tomography, we...
Abstract Lithospheric seismic anisotropy illuminates mid‐ocean ridge dynamics and the thermal evolution of oceanic plates. We utilize short‐period (5–7.5 s) ambient‐noise surface waves 15‐ to 150‐s Rayleigh measured across NoMelt ocean‐bottom array invert for complete radial azimuthal in upper ∼35 km ∼70‐Ma Pacific lithospheric mantle, through underlying asthenosphere. Strong variations Rayleigh‐ Love‐wave velocity are observed, including first clearly 2 θ 4 variations. Inversion averaged...
Abstract The NoMelt experiment imaged the mantle beneath 70 Ma Pacific seafloor with aim of understanding transition from lithosphere to underlying convecting asthenosphere. Seafloor magnetotelluric data four stations were analyzed using 2‐D regularized inverse modeling. preferred electrical model for region contains an 80 km thick resistive (>10 3 Ωm) a less (∼50 is isotropic and lacks highly conductive (≤10 layer under that would be indicative partial melt. We first examine temperature...
Abstract The Lake Malawi (Nyasa) Rift, in the East African Rift System (EARS), is an ideal modern analogue for study of extensional tectonic systems low strain rate settings. seismically active rift contains 700-m-deep Malawi, one world’s oldest and largest freshwater lakes with most diverse endemic faunal assemblages on Earth. Modern reprocessed legacy multichannel seismic-reflection data are constrained by velocity information from a wide-angle seismic experiment to evaluate variability...
SUMMARY A new amphibious seismic data set from the Cascadia subduction zone is used to characterize lithosphere structure Juan de Fuca ridge Cascades backarc. These are allowing imaging of an entire tectonic plate its creation at through onset beyond volcanic arc, along strike zone. We develop a tilt and compliance correction procedure for ocean-bottom seismometers that employs automated quality control calculate robust station noise properties. To elucidate crust upper-mantle structure, we...
Abstract Although the deep, wide basins of Western rift, Africa, have served as analogues for evolution half‐graben basins, geometry and kinematics border, intrabasinal, transfer fault systems been weakly constrained. Despite >100‐km‐long bounding little was known seismicity patterns or potential M > 7.5 earthquakes. Using our new local earthquake database from 2013‐2015 Study Extension maGmatism in Malawi aNd Tanzania (SEGMeNT) seismic array (57 onshore, 32 lake‐bottom stations)...
Abstract The North Basin of the Malawi Rift is an active, early‐stage rift segment that provides opportunity to quantify cumulative and recent faulting patterns in a young rift, assess contributions intrarift faults accommodating opening, examine controls on spatial faulting. Multichannel seismic reflection data acquired Lake (Nyasa) 2015 together with legacy multichannel image system synthetic within this border‐fault‐bounded, half‐graben basin. A dense wide‐angle reflection/refraction dip...
Located at the southernmost sector of Western Branch East African Rift System, Malawi exemplifies an active, magma-poor, weakly extended continental rift. To investigate controls on rifting, we image crustal and uppermost mantle structure beneath region using ambient-noise teleseismic Rayleigh-wave phase velocities between 9 100 s period. Our study includes six lake-bottom seismometers located in Lake (Nyasa), first time have been deployed any rift lakes. Noise levels lake are lower than...
Abstract The Alaska Amphibious Community Seismic Experiment (AACSE) is a shoreline-crossing passive- and active-source seismic experiment that took place from May 2018 through August 2019 along an ∼700 km long section of the Aleutian subduction zone spanning Kodiak Island Peninsula. featured 105 broadband seismometers; 30 were deployed onshore, 75 offshore in Ocean Bottom Seismometer (OBS) packages. Additional strong-motion instruments also at six onshore sites. Offshore OBS stretched outer...
SUMMARY In December, 2009, a rare sequence of earthquakes initiated within the weakly extended Western Rift East African system in Karonga province northern Malawi, providing unique opportunity to characterize active deformation associated with intrabasinal faults an early-stage rift. We combine teleseismic and regional seismic recordings largest events, InSAR imagery primary sequence, aftershocks from temporary (4-month) local network six seismometers delineate extent geometry faulting. The...
Phase delays of Rayleigh and Love waves from teleseismic earthquakes recorded during the Southern Africa Seismic Experiment have been inverted for upper‐mantle seismic velocities along propagation paths beneath station array. Successful models subarray structure displayed significant radial anisotropy in uppermost mantle but no shear‐wave low‐velocity zone, supporting hypothesis that lithosphere Kaapvaal craton is thick. The azimuthal variations Rayleigh‐wave slowness are not consistent with...
Seismic waves are used to explore large‐scale radial structure and lateral heterogeneity of shear velocity in the D″ region, chemical thermal boundary layer at base mantle. We analyze long‐period, horizontally polarized ( SH ) waveforms from earthquakes northwest Pacific recorded Europe Middle East for evidence proposed laterally varying stratification beneath Eurasia. Specifically, our data sample lower mantle extending Arctic Ocean near Novaya Zemlya, USSR, under northern India. Using a...
Between June 2003 and September 2005, 20 broadband, three‐component seismometers were deployed along the MacKenzie‐Liard Highway in Canada's Northwest Territories as part of joint Lithoprobe‐IRIS Canada Experiment (CANOE). These stations traverse a paleo‐Proterozoic suture subduction zone that has been previously documented to mantle depths using seismic reflection profiling. Teleseismic receiver functions computed from ∼250 earthquakes clearly reveal response ancient zone. On radial...
Abstract Southeast Papua hosts the world's youngest ultra‐high‐pressure (UHP) metamorphic rocks. These rocks are found in an extensional setting core complexes. Competing theories of shear zones or diapiric upwelling have been suggested as driving their exhumation. To test these theories, we analyze CDPAPUA temporary array 31 land and 8 seafloor broadband seismographs. Seismicity shows that deformation is being actively accommodated on complex bounding faults, offset by transfer structures a...
Abstract We present new constraints on rift basin structure in the northern Malawi Rift from a 3‐D compressional velocity model to investigate border fault geometry, accommodation zone structure, and role of preexisting structures underpinning this system. The uses observations first wide‐angle refraction study conducted using lake‐bottom seismometers one East African great lakes. is flanked by basin‐bounding faults crosses several significant remnant structures, making it an ideal location...