Publications
74 results found
Schlaphorst D, Kendall JM, Collier JS, et al., 2016, Water, oceanic fracture zones and the lubrication of subducting plate boundaries - insights from seismicity, Geophysical Journal International, Vol: 204, Pages: 1405-1420, ISSN: 0956-540X
We investigate the relationship between subduction processes and related seismicity for the Lesser Antilles Arc using the Gutenberg-Richter law. This power lawdescribes the earthquakemagnitude distribution, with the gradient of the cumulative magnitude distribution being commonly known as the b-value. The Lesser Antilles Arc was chosen because of its alongstrike variability in sediment subduction and the transition from subduction to strike-slip movement towards its northern and southern ends. The data are derived from the seismicity catalogues from the Seismic Research Centre of The University of the West Indies and the Observatoires Volcanologiques et Sismologiques of the Institut de Physique du Globe de Paris and consist of subcrustal events primarily from the slab interface. The b-value is found using a Kolmogorov-Smirnov test for a maximum-likelihood straight line-fitting routine. We investigate spatial variations in b-values using a grid-search with circular cells as well as an along-arc projection. Tests with different algorithms and the two independent earthquake cataloges provide confidence in the robustness of our results. We observe a strong spatial variability of the b-value that cannot be explained by the uncertainties. Rather than obtaining a simple north-south b-value distribution suggestive of the dominant control on earthquake triggering being water released from the sedimentary cover on the incoming American Plates, or a b-value distribution that correlates with on the obliquity of subduction, we obtain a series of discrete, high b-value 'bull's-eyes' along strike. These bull's-eyes, which indicate stress release through a higher fraction of small earthquakes, coincide with the locations of known incoming oceanic fracture zones on the American Plates. We interpret the results in terms of water being delivered to the Lesser Antilles subduction zone in the vicinity of fracture zones providing lubrication and thus changing the character of the related
Collier JS, Oggioni F, Gupta S, et al., 2015, Streamlined islands and the English Channel megaflood hypothesis, Global and Planetary Change, Vol: 135, Pages: 190-206, ISSN: 0921-8181
Recognising ice-age catastrophic megafloods is important because they had significant impact on large-scale drainage evolution and patterns of water and sediment movement to the oceans, and likely induced very rapid, short-term effects on climate. It has been previously proposed that a drainage system on the floor of the English Channel was initiated by catastrophic flooding in the Pleistocene but this suggestion has remained controversial. Here we examine this hypothesis through an analysis of key landform features. We use a new compilation of multi- and single-beam bathymetry together with sub-bottom profiler data to establish the internal structure, planform geometry and hence origin of a set of 36 mid-channel islands. Whilst there is evidence of modern-day surficial sediment processes, the majority of the islands can be clearly demonstrated to be formed of bedrock, and are hence erosional remnants rather than depositional features. The islands display classic lemniscate or tear-drop outlines, with elongated tips pointing downstream, typical of streamlined islands formed during high-magnitude water flow. The length-to-width ratio for the entire island population is 3.4 ± 1.3 and the degree-of-elongation or k-value is 3.7 ± 1.4. These values are comparable to streamlined islands in other proven Pleistocene catastrophic flood terrains and are distinctly different to values found in modern-day rivers. The island geometries show a correlation with bedrock type: with those carved from Upper Cretaceous chalk having larger length-to-width ratios (3.2 ± 1.3) than those carved into more mixed Paleogene terrigenous sandstones, siltstones and mudstones (3.0 ± 1.5). We attribute these differences to the former rock unit having a lower skin friction which allowed longer island growth to achieve minimum drag. The Paleogene islands, although less numerous than the Chalk islands, also assume more perfect lemniscate shapes. These lithologies therefore
Collier J, 2015, Q&A: Jenny Collier:, Astronomy & Geophysics, Vol: 56, Pages: 5.39-5.39, ISSN: 1366-8781
Garcia-Moreno D, Verbeeck K, Camelbeeck T, et al., 2015, Fault activity in the epicentral area of the 1580 Dover Strait (Pas-de-Calais) earthquake (northwestern Europe), Geophysical Journal International, Vol: 201, Pages: 528-542, ISSN: 1365-246X
On 1580 April 6 one of the most destructive earthquakes of northwestern Europe took placein the Dover Strait (Pas de Calais). The epicentre of this seismic event, the magnitude ofwhich is estimated to have been about 6.0, has been located in the offshore continuationof the North Artois shear zone, a major Variscan tectonic structure that traverses the DoverStrait. The location of this and two other moderate magnitude historical earthquakes in theDover Strait suggests that the North Artois shear zone or some of its fault segments may bepresently active. In order to investigate the possible fault activity in the epicentral area ofthe AD 1580 earthquake, we have gathered a large set of bathymetric and seismic-reflectiondata covering the almost-entire width of the Dover Strait. These data have revealed a broadstructural zone comprising several subparallel WNW–ESE trending faults and folds, some ofthem significantly offsetting the Cretaceous bedrock. The geophysical investigation has alsoshown some indication of possible Quaternary fault activity. However, this activity only appearsto have affected the lowermost layers of the sediment infilling Middle Pleistocene palaeobasins.This indicates that, if these faults have been active since Middle Pleistocene, their slip ratesmust have been very low. Hence, the AD 1580 earthquake appears to be a very infrequentevent in the Dover Strait, representing a good example of the moderate magnitude earthquakesthat sometimes occur in plate interiors on faults with unknown historical seismicity.
McGonigle C, Collier JS, 2014, Interlinking backscatter, grain size and benthic community structure, Estuarine, Coastal and Shelf Science, Vol: 147, Pages: 123-136, ISSN: 0272-7714
The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image- and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used: 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classification) from Quester Tangent Corporation Multiview software. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically defined groups are examined using ANOVA and PERMANOVA+. Results for the Hamon grab stations indicate significant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p < 0.001). Results for the Clamshell grab for two of the methods have stronger positive correlations; mean backscatter intensity (r2 = 0.619; p < 0.001) and angular response predicted mean grain size (r2 = 0.692; p < 0.001). ANOVA reveals significant differences in mean grain size (Hamon) within acoustic groups for all methods: mean backscatter (p < 0.001), angular response predicted grain size (p < 0.001), and QTC class (p = 0.009). Mean grain size (Clamshell) shows a significant difference between groups for mean backscatter (p = 0.001); other methods were not significant. PERMANOVA for the Hamon abundance shows benthic community structure was significantly different between acoustic groups for all methods (p ≤ 0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the C
Collier J, 2014, Review of ‘Mid-Ocean Ridges’., Geophysical Journal International, Vol: 197, Pages: 1884-1884, ISSN: 0956-540X
Hammond JOS, Kendall J-M, Collier JS, et al., 2013, The extent of continental crust beneath the Seychelles, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 381, Pages: 166-176, ISSN: 0012-821X
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- Citations: 18
Hammond JOS, Collier JS, Kendall J-M, et al., 2012, Anomalous lithosphere beneath theSeychelles: Seismic images of a ‘plume scar’, Earth and Planetary Science Letters, Vol: 355-356, Pages: 20-31
Armitage JJ, Collier JS, Minshull TA, et al., 2011, Thin oceanic crust and flood basalts: India-Seychelles breakup, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, Vol: 12
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- Citations: 33
Collier JS, Humber SR, 2011, Fringing reefs of the Seychelles inner granitic islands, Western Indian Ocean, Seafloor Geomorphology As Benthic Habitat, Editors: Harris, Baker, Amsterdam, Pages: 339-347
Collier J, 2010, Splitting continents, Planet Earth, Pages: 26-27, ISSN: 1479-2605
Jenny Collier describes how her team is doing research work to know why providing some pairs of continents trigger lots of volcanoes when they break apart, while others do not. The consensus among scientists before her team's work was that these very different styles of break-up are controlled by the temperature of the mantle beneath the separating continents. They arranged for geophysical instruments from four different organizations to be delivered in three 30ft containers. Planning for the cruise in 2002 and 2003 was tense, with the build-up to the Iraq war resulting in several changes to their port and start date. One highlight for the novice sailors on board was an ancient maritime initiation to mark their first crossing the line with a colorful ceremony in which the ship's crew played the traditional roles of Neptune and his court.
Armitage JJ, Collier JS, Minshull TA, 2010, The importance of rift history for volcanic margin formation, NATURE, Vol: 465, Pages: 913-917, ISSN: 0028-0836
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- Citations: 70
Collier JS, Minshull TA, Hammond JOS, et al., 2009, Factors influencing magmatism during continental breakup: New insights from a wide-angle seismic experiment across the conjugate Seychelles-Indian margins, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 114, ISSN: 2169-9313
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- Citations: 51
Collier JS, Sansom V, Ishizuka O, et al., 2008, Age of Seychelles-India break-up, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 272, Pages: 264-277, ISSN: 0012-821X
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- Citations: 160
Minshull TA, Lane CI, Collier JS, et al., 2008, The relationship between rifting and magmatism in the northeastern Arabian Sea, NATURE GEOSCIENCE, Vol: 1, Pages: 463-467, ISSN: 1752-0894
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- Citations: 74
Brown CJ, Collier JS, 2008, Mapping benthic habitat in regions of gradational substrata: An automated approach utilising geophysical, geological, and biological relationships, ESTUARINE COASTAL AND SHELF SCIENCE, Vol: 78, Pages: 203-214, ISSN: 0272-7714
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- Citations: 86
Gupta S, Collier JS, Palmer-Felgate A, et al., 2007, Catastrophic flooding origin of shelf valley systems in the English Channel, NATURE, Vol: 448, Pages: 342-U5, ISSN: 0028-0836
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- Citations: 188
Collier JS, Humber S R, 2007, Time-lapse side-scan sonar imaging of bleached coral reefs: a case study from the Seychelles, Remote Sensing of Environment, Vol: 108, Pages: 339-356, ISSN: 0034-4257
Collier JS, Gupta S, Potter G, et al., 2006, Using bathymetry to identify basin inversion structures on the English Channel shelf, GEOLOGY, Vol: 34, Pages: 1001-1004, ISSN: 0091-7613
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- Citations: 14
Lonergan L, Maidment S, Collier J, 2006, Pleistocene subglacial tunnel valleys in the central North Sea basin: 3-D morphology and evolution, Journal of Quaternary Science, Vol: 21, Pages: 891-903, ISSN: 0267-8179
Collier JS, Brown CJ, 2005, Correlation of sidescan backscatter with grain size distribution of surficial seabed sediments, MARINE GEOLOGY, Vol: 214, Pages: 431-449, ISSN: 0025-3227
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- Citations: 160
Collier JS, Minshull TA, Kendall JM, et al., 2004, Rapid continental breakup and microcontinent formation in the western Indian Ocean, EOS, Vol: 85
Collier JS, Watts AB, 2001, Lithospheric response to volcanic loading by the Canary Islands: constraints from seismic reflection data in their flexural moat, GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 147, Pages: 660-676, ISSN: 0956-540X
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- Citations: 47
Collier JS, 2001, Sidescan sonar imaging of bleached coral reefs in the Seychelles, Shoals of Capricorn Marine Science, Training and Education in the Western Indian Ocean, Field Report 1998-2001, Publisher: Royal Geographical Society (with the Institute of British Geographers), ISBN: 0-907649-90-4
Hayward N, Watts AB, Westbrook GK, et al., 1999, A seismic reflection and GLORIA study of compressional deformation in the Gorringe Bank region, eastern North Atlantic, GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 138, Pages: 831-850, ISSN: 0956-540X
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- Citations: 73
Collier JS, Singh SC, 1998, Poisson's ratio structure of young oceanic crust, Journal of Geophysical Research: Solid Earth, Vol: 103, Pages: 20981-20996, ISSN: 2169-9313
We have applied full waveform inversion to wide-aperture seismic reflection data from the southern East Pacific Rise near 14° S. The data contain clear compressional wave and doubly converted shear wave arrivals that provide good constraints on the P and S -wave velocities (Vp, Vs, and hence Poisson's ratio σ) and seismic attenuation (Qp, Qs) structure of seismic layer 2. Layer 2A is highly attenuating (Qp=18-30 and Qs=8-15) and layer 2B is moderately attenuating (Qp=30-50 and Qs=20-25). Our results show high σ at the seafloor and in layer 2A (σ=0.48). Across the top of the 2A/B transition the rapid increase in Vp is accompanied by a sharp drop in σ to 0.25 within just 200 m of the seafloor. We perform simple calculations to gain an insight into the porosity and crack distribution with depth. These calculations suggest that porosity is in excess of 30% in layer 2A but reduces to 6-7% at the top of the 2A/B transition and to about 5% at a depth of 600 m below seafloor within layer 2B. Our results suggest that there is an increase in the average aspect ratio with depth across the 2A/B transition. The most likely explanation is that numerous thin cracks either mechanically close or are infilled at depth. Our results show there to be an abrupt change in the pore structure across the 2A/B transition which is consistent with a lithologic transition from extrusives to dykes but is equally consistent with a transition (mechanical or hydrothermal) within the extrusive pile.
Singh SC, Kent GM, Collier JS, et al., 1998, Melt to mush variations in crustal magma properties along the ridge crest at the southern East Pacific Rise, NATURE, Vol: 394, Pages: 874-878, ISSN: 0028-0836
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- Citations: 132
Collier JS, 1998, A seismic inversion study of the axial magma chamber reflector beneath the East Pacific Rise near 10 N, Modern Ocean Floor Processes and the Geological Record, Publisher: Geological Society of London, ISBN: 9781862390232
Collier JS, Henstock TJ, Peirce C, et al., 1998, A detailed geophysical study in the Canary Basin (eastern Atlantic) : implications for the internal structure of 130 Ma oceanic crust, Geophysical Journal International, Vol: 135, Pages: 943-963
Singh SC, Kent GM, Collier JS, et al., 1998, Melt to mush variations in crustal magma properties along the ridge crest at the southern East Pacific Rise, Nature, Vol: 394, Pages: 874-878
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