A5014652050- earthquake and tectonic studies
- Geological and Geochemical Analysis
- High-pressure geophysics and materials
- Seismic Imaging and Inversion Techniques
- Seismic Waves and Analysis
- Geological and Geophysical Studies
- Methane Hydrates and Related Phenomena
- Seismology and Earthquake Studies
- Hydrocarbon exploration and reservoir analysis
- Geological formations and processes
- Geology and Paleoclimatology Research
- Landslides and related hazards
- Geological Studies and Exploration
- Geological Modeling and Analysis
- Cryospheric studies and observations
- Reservoir Engineering and Simulation Methods
- Drilling and Well Engineering
- Paleontology and Stratigraphy of Fossils
- Hydraulic Fracturing and Reservoir Analysis
- Geotechnical and Geomechanical Engineering
- Geophysics and Gravity Measurements
- Geophysics and Sensor Technology
- Earthquake Detection and Analysis
- Underwater Acoustics Research
- Geological and Geophysical Studies Worldwide
University of Cambridge
2015-2025
RELX Group (United States)
2018
University of Iceland
2001-2016
Istituto Nazionale di Geofisica e Vulcanologia
2009
Durham University
2006
Bridge University
1977-2003
Hokkaido University
2001
The University of Tokyo
2001
National Oceanography Centre
1996-2001
University of Southampton
2001
When continents rift to form new ocean basins, the rifting is sometimes accompanied by massive igneous activity. We show that production of magmatically active rifted margins and effusion flood basalts onto adjacent can be explained a simple model above thermal anomaly in underlying mantle. The rocks are generated decompression melting hot asthenospheric mantle as it rises passively beneath stretched thinned lithosphere. Mantle plumes generate regions lithosphere typically 2000 km diameter...
Seismic refraction results show that the igneous section of oceanic crust averages 7.1±0.8 km thick away from anomalous regions such as fracture zones and hot‐spots, with extremal bounds 5.0–8.5 km. Rare earth element inversions melt distribution in mantle source region suggest sufficient is generated under normal spreading centers to produce an 8.3±1.5 crust. The difference between thickness estimates seismics rare not significant given uncertainties composition, though it magnitude would...
We discuss the geological, geophysical, and petrological observations that constrain nature of mantle convection in plumes, show how theoretical models plumes have developed over past three decades. The large volumes lava emplaced geologically short periods as flood basalts are generated mainly by decompression melting abnormally hot brought to base lithosphere plumes. present new results from application McKenzieand O'Nions' (1991) rare earth element inversion scheme geochemistry infer...
We describe results from 200 heat flow measurements across the Cape Verde Rise in North Atlantic. They show that through normal, 125 Myr-old crust is 45.5 ± 3.4mWm-2, close to prediction for a lithospheric plate model. Heat increases towards centre of Rise, reaching maximum 16 4 mW m-2 above normal oceanic value. The concommitant geoid anomaly at 7.6 0.3 m and depth 1900 m. anomalous flow, bathymetric values are used constrain variety theoretical models hot spot mechanisms. Lithospheric...
Seismic refraction data from mature oceanic regions show remarkable consistency in crustal thickness between sites, yet the characteristics of different spreading centers great variation. This leads to paradox that similarity crust suggests igneous processes accretion are same across a range rates but differences themselves imply opposite. We have developed simple two dimensional model for at by episodic addition sills high level within crust, as implied recent geophysical studies centers....
Abstract Decompression melting of hot mantle rising in the convectively driven core Iceland plume generates igneous crust beneath that is c. 25 km thick. Passive decompression adjacent Reykjanes Ridge spreading centre produces 7–10 The decrease between and oceanic crustal thickness, basement elevation column thickness deduced from rare earth element inversions basaltic rocks, suggests markedly cooler (potential temperature less than 1400°C) under 1500 °C). We suggest fed by a sheath...
We describe a new model for melt generation by mantle decompression during uniform pure shear extension of continental lithosphere at finite rates. As the duration rifting increases, conductive heat loss from up welling causes amount generated beneath rift to decrease. Melt is strongly dependent on because most in region near top upwelling asthenosphere, where cooling greatest when extended rate. Whereas instantaneous thinning factor 5 generates more than 2 km as underlying normal...
The Makran continental margin in the Gulf of Oman forms seaward extremity an accretionary sediment prism which extends several hundred kilometers inland. A recently acquired multichannel seismic reflection profile shot across imaged structure greater detail than was previously possible and allowed us to investigate relationship between deformation pore fluid motion region. Velocity analyses common midpoint gathers reveal a marked change velocity at toe wedge, as seen previous sonobuoy...
The Proterozoic Midcontinent Rift System of North America is remarkably similar to Phanerozoic rifted continental margins and flood basalt provinces. Like the younger analogues, volcanism within this older rift can be explained by decompression melting rapid extrusion igneous material during lithospheric extension above a broad, asthenospheric, thermal anomaly which we call Keweenaw hot spot. Great Lakes International Multidisciplinary Program on Crustal Evolution seismic reflection profiles...
Abstract Over a 13 day period magma propagated laterally from the subglacial Bárðarbunga volcano in northern rift zone, Iceland. It created > 30,000 earthquakes at 5–7 km depth along 48 path before erupting on 29 August 2014. The seismicity, which tracked dike propagation, advanced short bursts 0.3–4.7 km/h separated by pauses of up to 81 h. During each surge forward, seismicity behind tip dropped. Moment tensor solutions leading edge show exclusively left‐lateral strike‐slip faulting...
Earthquakes are commonly located by linearized inversion of discrete arrival time picks made from signals recorded at a network seismic stations. If mis-picks made, these will contribute to the location, therefore causing potential bias. For data dense array, direct imaging methods can be applied instead. We describe 'coalescence microseismic mapping' method, which is bridge between two approaches and operate with continuously on sparse array. By mapping scalar derived envelope arrivals we...
We show that there is a strong and consistent correlation between geochemical geophysical estimates of the amount melt generated in mantle beneath oceanic ridges. This holds across all spreading rates on scales down to size individual ridge segments. There an abrupt decrease at full below ∼20 mm/a. Our observations are with conclusion <10% frozen before it reaches crust serpentine probably represents only small percentage material above Moho. The well mixed segment scale, high-level magma...
Results from the Färoe‐Iceland Ridge Experiment (FIRE) constrain crustal thickness as 19 km under Northern Volcanic Zone of Iceland and 35 older Tertiary areas northeastern Iceland. The Moho is defined by strong P wave S reflections. Synthetic seismogram modeling reflection indicates mantle velocities at least 8.0 km/s beneath 7.9 neovolcanic zone. Crustal diving rays resolve structure upper lower crust. Surface are 1.1–4.0 in Quaternary rocks rather higher, 4.4–4.7 km/s, basalts that...
A seismic refraction transect across the Galicia Bank continental margin shows that original crust thins westward from 17 to 2 km immediately east of a margin‐parallel peridotite ridge (PR). Immediately west PR, oceanic is only 2.5–3.5 thick, but farther (oceanward) it thickens 7 km. The PR caps ∼60‐km‐wide lens‐shaped serpentinized body underlying both thinned and thin crust. When superimposed on reflection time version velocity model, S reflector clearly intracrustal at its end. Westward,...
The seismic velocity structure of the Krafla central volcano is characterized by large variations in compressional velocity. A 40 km wide high‐velocity dome extends from lower crust (11–14 depth) beneath narrowing upward. magma chamber sits at its top near 3 depth. It defined both 0.2–0.3 s wave delays and shear shadowing to be 2–3 N‐S, 8–10 E‐W, 0.7–1.8 thick. near‐surface (uppermost 2.5 km) caldera approximately flat‐lying, with only minor lateral heterogeneities. has low attenuation...
Seismic studies have established that large‐offset transforms along the slow spreading Mid‐Atlantic Ridge exhibit anomalous crustal structures fall well outside range typically associated with oceanic crust. Seismically, fracture zone crust in North Atlantic is extremely heterogeneous both thickness and internal structure. It frequently quite thin (<1–2 km thick) characterized by low compressional wave velocities absence of a normal seismic layer 3. A more gradual thinning can extend up...
The crustal structure of central Iceland is modelled using data from a 310 km long refraction profile shot during summer 1995. traversed the Skagi Peninsula on north coast (surface rocks age 8.5–0.8 Myr) to southeast 8.5–3.3 Myr), crossing 3.3–0 over glacier Vatnajökull, below which locus mantle plume currently centred. thickness 25 at end profile, increasing 38–40 beneath southern Iceland. upper crust characterized by seismic P-wave velocities 3.2 approximately 6.4 s−1. At extreme ends can...
Enormous variations exist along rifted margins of the North Atlantic in magmatic activity that accompanied continental breakup. The exhibit a full range behaviour. One end spectrum (commonly termed ‘volcanic’ margins) is found northern off Greenland, Norway and northwest Britain, where huge volumes igneous rock were added to crust as it rifted, adjacent oceanic considerably thicker than normal. other (so-called ‘non-volcanic’ occurs further south France Spain, only minor volcanism rifting...