Rock Mechanics Laboratory (RML),
School of the Environment, Geography and Geosciences,
University of Portsmouth
Honorary research fellow, Rock & Ice Physics Laboratory (RIPL),
Department of Earth Sciences,
University College London
Contact: email@example.com or firstname.lastname@example.org
Volcanotectonics and Geohazards: I extended the methods above, for the first time, to investigate fluid-driven seismicity in the shallow crust with particular focus on passive (triggered) seismicity in active volcanoes. These earthquakes in volcanic settings (known as Volcano-Tectonic, Hybrid and Low Frequency harmonic events) are diagnostic of conditions under the volcano and frequently detected before unrest. A new understanding of their generation in terms of fluid pressure, speed, and volume is now allowing new models to be developed for this important geological hazard, and better understand the key role that fluids have on the stability of volcanic flanks.Fluid-induced fracture mechanics: Fluids moving within a sealed impermeable rock mass will ultimately lead to fracture and failure due to over-pressurisation. This is both a natural phenomenon (e.g. veining, diking), and exploited during intentional hydraulic fracture. My research has successfully developed novel new apparatus to safely simulate this process at elevated pressure and temperature. These important new experiments have deconstructed the links between the high-pressure rock mechanics, fracture tip stresses, and the generated fracture energy (seismicity). This provides valuable information impacting the design of deep geological resources (e.g. Geothermal energy) as well as preventing unwanted fracturing, reducing risk and hazard in heat-generating processes (e.g. deep geological storage of nuclear waste).
|Dynamic Laboratory simulations of fluid-rock coupling with application to volcano seismicity and unrest.
Pore fluids play a key role in how crustal rocks deform, particularly in a volcanic environment where fluids span a wide range of types, and exist across a wide spectrum of temperature, pressure, and phase, influenced by the presence of the magmatic system at depth. Not only do pressurized pore fluids affect the mechanical properties and the elastic velocities of the host rock mass (volcanic edifice), they are also responsible for the generation of a range of seismic signals, for example Low Frequency (LF) tremor and Volcano-Tectonic (VT) seismicity generated due to shear fracture. This project tests the hypothesis that the presence of pore fluid delays the fracturing and the onset of microseismic activity, possibly explaining the sudden increase of precursory seismic activity before volcanic eruptions, and how fluids homogenize the rock material, decreasing the elastic wave anisotropy as they flow inside the newly formed cracks. I simulated these porcesses using advanced servo-controlled triaxial testing apparatus and state-of-the-art acoustic emission (AE) instrumentation: AE signals are the laboratory analogue of field-scale earthquakes, allowing the physics of the macro-scale events to be controlled under known P/T conditions. The depressurization of fluids reveals how different fluid phases contributes to form different spectral peaks, characterizing the fluid-induced signals. Recently, we have explored and simulated Tornillo events during gas depressurization, representing a new key link between earthquake features (such as amplitude modulation) and a physical properties (such as pressure transients).
|Coupled fluid-fracture mechanics in the applied geosciences: mechanical, temperature, and viscosity effects.
This project tackles two inter-related themes: 1). The safe operation of unconventional reservoirs requires not only extensive knowledge of the tensile fracture mechanics of the rock mass, but also how permeable new fracture networks are to different fluid types. In addition, elevated pore fluid pressures have a significant effect on rock mass stability via the effective stress pronciple. To better understand these dual challenges, this project uses controlled laboratory methods to link measured permeability of freshly generated fracture networks to the fracture density and geometry across a range of fluid types (water/slick-water, and oil), and with reference to the microseismic response during initial fracture, which itself may be used as a proxy for damage and fracture zone properties. 2). Elevated pore fluid temperatures and viscosities may have a detrimental effect on the rock mass stability via the lowered wetting effect and pore fluid activity. To better understand these issues, this project extends the conditions in (1) above to elevated reservoir conditions (geothermal and/or hydrocarbon) up to approximately 200C. Fracture data (density and aperture) is correlated across a range of fluid viscosities and temperatures: impossible in the typical field scenario. In both cases samples of 40mm diameter and 100mm length are encapsulated in a rubber jacket fitted with an 3D array for micro-acoustic sensors and instrumented for axial and radial strain. A central axial borehole is then pressurised within an outer shell of rock to simulate a range of depths to 4km by using high pressure hydraulics. Fracture area and size is derived from the spatio-temporal data, validated by post-test X-ray Computed Tomography.
|Fracture and permeability evolution of geothermal reservoirs using elastic moduli and elastic wave velocity (with EDC Ltd. and Northeastern Univ, CN).
Seismic based geophysical methods are seeing increased usage in evaluating geothermal resources in order to maximize resource potential. However, interpreting geophysical data (such as modulus and fracture density/alignment) generated from geothermal reservoirs remains difficult. This collaboration focuses on producing new laboratory data of seismic attributes of fresh and hydrothermally altered rocks from a Philippine geothermal field (Southern Negros Geothermal Project - SNGP). Two types of rocks were obtained by sub-coring samples of low porosity (~1%) andesite and higher porosity (~10%) volcaniclastic samples from the SNGP. The formation of shear fractures that weakens the material decreases the attributes while increasing pressure conditions that strengthens the material via fracture closure increases the overall properties. Samples are prepared with two offset drill holes to allow a natural fracture to permit fluid flow along the fracture. An embedded array of Acoustic Emission (AE) sensors allows elastic wave and induced microseismic data to be collected. Ultimately, the improved monitoring of geothermal reservoirs with seismic sensors (AE in the laboratory) has the potential to resolve both the 4D source and character of the event (e.g. source mechanism, frequency vs magnitude). Larger scale implementation of this would therefore be of benefit in understanding associated geohazards in high temperature geothermal fields.
|Investigating dynamic fracture processes in 'weak' volcanic rocks: applications to volcano seismology and forecasting (with UWE Bristol, Dias (Dublin) and UCL Hazard Centre).
Volcano seismicity is an important tool in remotely monitoring and forecasting activity at volcanoes around the world. Volcanic earthquakes show diverse spectral characteristics, with shallow Long Period (Low Frequency) seismicity and long duration tremor generally interpreted as indicators of rapid fluid migration in fractures and faults, sometimes detected before eruption. This ongoing collaboration investigates how low-cohesion volcanic sediment from Campi Flegrei caldera (Italy) produces Low Frequency and long duration seismicity whilst undergoing deformation in dry conditions. Correlated X-Ray tomography of samples before and after deformation constrain the source as distributed damage. We have generated new evidence that Low Frequency events can be an indicator of slow-deformation within the edifice without fluids. Instead, strain is accommodated by weak volcaniclastic materials, particularly at low strain rates and confining pressures. This may relate to why low frequency seismicity is not always associated with eruption. Given the frequent observation of shallow ground deformation in volcanic settings, it seems likely the conditions for subjecting volcanic sediments to these types of conditions are widespread. We interpret these data by mapping/modelling the cumulative tensile stresses in order to better understand the cumulative energy in the volcanic system, and how this may be better used to forecast instability using field seismic data.
|Tensile driven fracturing in Volcano-tectonic settings: On the interplay of dyke injection and edifice stability (with Universities of Mainz and Turin).
This ongoing collaboration aims to simulate high pressure and high temperature processes operating during dyke movement in volcanic settings. Knowledge of this process is key to better understanding the eruption of magma, and how the stability of the volcanic edifice (rock mass) is influenced during the movement and emplacement of dyke swarms. Examples of unstable rock masses include volcano flank collapse problems as seen at Etna, Stromboli and El Hierro. We use a variety of methods including laboratory rock deformation and rock physics, remote sensing, and numerical situations to better understand the interaction between the soft magma and underlying sediments (e.g. carbonates and limestones particularly in the case of Mt Etna), and the harder basalts and other volcano products. We posit that the overall rock mass stability is governed not only by the hard layers but also eye the underlying softer sediments, and the fluids (including mamas) injected into these complex layered structures. In addition, cyclical stress regimes common in volcano settings may allow damage accumulation bu build up without warning resulting in catastrophic failure with little warning.
|Integrating multi-scale tomography techniques for determining the physical properties of the Earth from laboratory experiments to field scale (with UCL-HC, Mainz, Turin and INGV).
Scaling in the Earth sciences represents a fundamental and ongoing challenge. Structures in volcanotectonics typically cover a large range of scales typically across the hundreds of meters to km scales. However, laboratory methods are at best in dm (fraction of metre scale) but have the key advantage that conditions (pressure, temperature, strain) may be imposed and controlled to develop new theories. Linking these scales requires numerical models, geophysical data, and scale invariant methods to bridge these key gaps. In this ongoing collaborative project between Portsmouth, UCL Hazard Centre, INGV and the universities of Mainz and Turin, a series of new experiments, methods, and numerical approaches are being combined to better understand the underpinning science of calling across different geophysical parameters. Ultimately, these new data may be applied to updated fracture forecasting models and eruption prediction tools in volcano geophysics. We particularly focus on the volcanoes of St. Helens and the Campi Flegrei caldera (Italy) to test these ideas.
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 King, T., Benson, P.M., and De Siena, L., Vinciguerra, S. (2020). Acoustic emission waveform picking with time-delay neural networks during rock deformation laboratory experiments (2020). In press at Seismological Research Letters. https://doi.org/
 Benson, P. M., Austria, D. C., Gehne, S., Butcher, E., Harnett, C. E., Fazio, M., and Tomas, R. (2020). Laboratory simulations of fluid-induced seismicity, hydraulic fracture, and fluid flow. Geomechanics for Energy and the Environment, 100169. https://doi.org/10.1016/j.gete.2019.100169
 Gehne, S., Forbes Inskip, N. D., Benson, P. M., Meredith, P. G., & Koor, N. (2020). Fluid-Driven Tensile Fracture and Fracture Toughness in Nash Point Shale at Elevated Pressure. Journal of Geophysical Research: Solid Earth, 125(2), 1-11. https://doi.org/10.1029/2019jb018971
 King, T, L. De Siena, P.M. Benson, and S. Vinciguerra (2020), Mapping Faults with Seismic Scattering: A Laboratory Analogue. Accepted to J. Geophys. Res. (solid Earth) Walsh volume, in press.
 Gehne, S., Benson, P. M., Koor, N., Dobson, K. J., Enfield, M., & Barber, A. (2019). Seismo-Mechanical Response of Anisotropic Rocks Under Hydraulic Fracture Conditions: New Experimental Insights. Journal of Geophysical Research: Solid Earth, 124(9), 9562-9579. https://doi.org/10.1029/2019JB017342
 Gehne, S., & Benson, P. M. (2019). Permeability enhancement through hydraulic fracturing: laboratory measurements combining a 3D printed jacket and pore fluid over-pressure. Scientific Reports, 9(1). https://doi.org/10.1038/s41598-019-49093-1
 Emily Butcher , Andrew Gibson, Philip M. Benson, N. K. and, & Swift, G. (2019). Near infrared spectroscopic measurement of strain in rocks. Journal of Near Infrared Spectroscopy, 27(6), 430-438. https://doi.org/10.1177/0967033519872540
 Fazio, M., Alparone, S., Benson, P. M., Cannata, A., & Vinciguerra, S. (2019). Genesis and mechanisms controlling tornillo seismo-volcanic events in volcanic areas. Scientific Reports, 9(1). https://doi.org/10.1038/s41598-019-43842-y
 Bakker, R. R., Violay, M. E. S., Vinciguerra, S., Fazio, M., & Benson, P. M. (2019). Constitutive Laws for Etnean Basement and Edifice Lithologies. Journal of Geophysical Research: Solid Earth, 124(10), 10074-10088. https://doi.org/10.1029/2019JB017399
 Castagna, A., Ougier-Simonin, A., Benson, P. M., Browning, J., Walker, R. J., Fazio, M., & Vinciguerra, S. (2018). Thermal Damage and Pore Pressure Effects of the Brittle-Ductile Transition in Comiso Limestone. Journal of Geophysical Research: Solid Earth, 123(9), 7644-7660. https://doi.org/10.1029/2017JB015105
 Colombero, C., Comina, C., Vinciguerra, S., & Benson, P. M. (2018). Microseismicity of an Unstable Rock Mass: From Field Monitoring to Laboratory Testing. Journal of Geophysical Research: Solid Earth, 123(2), 1673-1693. https://doi.org/10.1002/2017JB014612
 King, T., Benson, P. M., De Siena, L., & Vinciguerra, S. (2017). Investigating the apparent seismic diffusivity of near-receiver geology at mount St. Helens Volcano, USA. Geosciences (Switzerland), 7(4). https://doi.org/10.3390/geosciences7040130
 Harnett, C. E., Benson, P. M., Rowley, P., & Fazio, M. (2018). Fracture and damage localization in volcanic edifice rocks from El Hierro, Stromboli and Tenerife. Scientific Reports, 8(1). https://doi.org/10.1038/s41598-018-20442-w
 Gehne, S., & Benson, P. M. (2017). Permeability and permeability anisotropy in Crab Orchard sandstone: Experimental insights into spatio-temporal effects. Tectonophysics, 712-713, 589-599. https://doi.org/10.1016/j.tecto.2017.06.014
 Fazio, M., Benson, P. M., & Vinciguerra, S. (2017). On the generation mechanisms of fluid-driven seismic signals related to volcano-tectonics. Geophysical Research Letters, 44(2), 734-742. https://doi.org/10.1002/2016GL070919
 Ghaffari, H. O., Griffith, W. A., & Benson, P. M. (2017). Microscopic evolution of laboratory volcanic hybrid earthquakes. Scientific Reports, 7. https://doi.org/10.1038/srep40560
 Bakker, R. R., Fazio, M., Benson, P. M., Hess, K. U., & Dingwell, D. B. (2016). The propagation and seismicity of dyke injection, new experimental evidence. Geophysical Research Letters, 43(5), 1876-1883. https://doi.org/10.1002/2015GL066852
 Ghaffari, H. O., Griffth, W. A., Benson, P. M., Xia, K., & Young, R. P. (2016). Observation of the Kibble-Zurek Mechanism in Microscopic Acoustic Crackling Noises. Scientific Reports. https://doi.org/10.1038/srep21210
 Bakker, R. R., Violay, M. E. S., Benson, P. M., & Vinciguerra, S. C. (2015). Ductile flow in sub-volcanic carbonate basement as the main control for edifice stability: New experimental insights. Earth and Planetary Science Letters, 430, 533-541. https://doi.org/10.1016/j.epsl.2015.08.017
 Kushnir, A. R. L., Kennedy, L. A., Misra, S., Benson, P., & White, J. C. (2015). The mechanical and microstructural behaviour of calcite-dolomite composites: An experimental investigation. Journal of Structural Geology, 70, 200-216. https://doi.org/10.1016/j.jsg.2014.12.006
 Benson, P. M., Vinciguerra, S., Nasseri, M. H. B., & Young, R. P. (2014). Laboratory simulations of fluid/gas induced micro-earthquakes: Application to volcano seismology. Frontiers in Earth Science, 2(4). https://doi.org/10.3389/feart.2014.00032
 Vallianatos, F., Michas, G., Benson, P. M., & Sammonds, P. (2013). Natural time analysis of critical phenomena: The case of acoustic emissions in triaxially deformed Etna basalt. Physica A: Statistical Mechanics and Its Applications, 392(20), 5172-5178. https://doi.org/10.1016/j.physa.2013.06.051
 Zappone, A. S., & Benson, P. M. (2013). Effect of phase transitions on seismic properties of metapelites: A new high-temperature laboratory calibration. Geology, 41(4), 463-466. https://doi.org/10.1130/G33713.1
 Lavallee, Y., Benson, P. M., Heap, M. J., Hess, K. U., Flaws, A., Schillinger, B., and Dingwell, D. B. (2013). Reconstructing magma failure and the degassing network of domebuilding eruptions. Geology, 41(4), 515-518. https://doi.org/10.1130/G33948.1
 Bruijn, R. H. C., Almqvist, B. S. G., Hirt, A. M., & Benson, P. M. (2013). Decoupling of paramagnetic and ferrimagnetic AMS development during the experimental chemical compaction of illite shale powder. Geophysical Journal International, 192(3), 975-985. https://doi.org/10.1093/gji/ggs086
 Benson, P. M., Heap, M. J., Lavallee, Y., Flaws, A., Hess, K. U., Selvadurai, A. P. S., and Schillinger, B. (2012). Laboratory simulations of tensile fracture development in a volcanic conduit via cyclic magma pressurisation. Earth and Planetary Science Letters, 349-350, 231-239. https://doi.org/10.1016/j.epsl.2012.07.003
 Nara, Y., Morimoto, K., Hiroyoshi, N., Yoneda, T., Kaneko, K., & Benson, P. M. (2012). Influence of relative humidity on fracture toughness of rock: Implications for subcritical crack growth. International Journal of Solids and Structures, 49(18), 2471-2481. https://doi.org/10.1016/j.ijsolstr.2012.05.009
 Vallianatos, F., Benson, P. M., Meredith, P., & Sammonds, P. (2012). Experimental evidence of a non-extensive statistical physics behaviour of fracture in triaxially deformed Etna basalt using acoustic emissions. EPL, 97(5). https://doi.org/10.1209/0295-5075/97/58002
 Lavallee, Y., Benson, P. M., Heap, M. J., Flaws, A., Hess, K. U., & Dingwell, D. B. (2012). Volcanic conduit failure as a trigger to magma fragmentation. Bulletin of Volcanology, 74(1), 11-13. https://doi.org/10.1007/s00445-011-0544-2
 Harrington, R. M., & Benson, P. M. (2011). Analysis of laboratory simulations of volcanic hybrid earthquakes using empirical Greens functions. Journal of Geophysical Research: Solid Earth, 116(11). https://doi.org/10.1029/2011JB008373
 Benson, P. M., Vinciguerra, S., Meredith, P. G., & Young, R. P. (2010). Spatio-temporal evolution of volcano seismicity: A laboratory study. Earth and Planetary Science Letters, 297(1-2), 315-323. https://doi.org/10.1016/j.epsl.2010.06.033
 de Rubeis, V., Vinciguerra, S., Tosi, P., Sbarra, P., & Benson, P. M. (2010). Acoustic Emission Spectra Classification from Rock Samples of Etna Basalt in Deformation-Decompression Laboratory Experiments. GeoPlanet: Earth and Planetary Sciences, 1, 201-211. https://doi.org/10.1007/978-3-642-12300-9_11
 Benson, P.M. (2010) in: Proofs, G., & Loa, M. Volcano seismicity in the laboratory. 2010 McGraw-Hill Yearbook of Science & Technology, (June 2009). https://doi.org/10.1036/1097-8542.YB100208
 Ying, W. L., Benson, P. M., & Young, R. P. (2009). Laboratory simulation of fluid-driven seismic sequences in shallow crustal conditions. Geophysical Research Letters, 36(20). https://doi.org/10.1029/2009GL040230
 Nasseri, M. H. B., Schubnel, A., Benson, P. M., & Young, R. P. (2009). Common evolution of mechanical and transport properties in thermally cracked westerly granite at elevated hydrostatic pressure. Pure and Applied Geophysics, 166(5-7), 927-948. https://doi.org/10.1007/s00024-009-0485-2
 Clark, R. A., Benson, P. M., Carter, A. J., & Moreno, C. A. G. (2009). Anisotropic P-wave attenuation measured from a multi-azimuth surface seismic reflection survey. Geophysical Prospecting, 57(5), 835-845. https://doi.org/10.1111/j.1365-2478.2008.00772.x
 Benson, P. M., Vinciguerra, S., Meredith, P. G., & Young, R. P. (2008). Laboratory simulation of volcano seismicity. Science, 322(5899), 249-252. https://doi.org/10.1126/science.1161927
 'Highlight' in: Burlini, L., & Di Toro, G. (2008). Geophysics: Volcanic symphony in the lab. Science, 322(5899), 207-208. https://doi.org/10.1126/science.1164545
 Townend, E., Thompson, B. D., Benson, P. M., Meredith, P. G., Baud, P., & Young, R. P. (2008). Imaging compaction band propagation in Diemelstadt sandstone using acoustic emission locations. Geophysical Research Letters, 35(15). https://doi.org/10.1029/2008GL034723
 Benson, P. M., Thompson, B. D., Meredith, P. G., Vinciguerra, S., & Young, R. P. (2007). Imaging slow failure in triaxially deformed Etna basalt using 3D acoustic-emission location and X-ray computed tomography. Geophysical Research Letters, 34(3). https://doi.org/10.1029/2006GL028721
 Benson, P. M., Meredith, P. G., & Schubnel, A. (2006). Role of void space geometry in permeability evolution in crustal rocks at elevated pressure. Journal of Geophysical Research: Solid Earth, 111(12). https://doi.org/10.1029/2006JB004309
 Jones, S., Benson, P. M., & Meredith, P. (2006). Pore fabric anisotropy: Testing the equivalent pore concept using magnetic measurements on synthetic voids of known geometry. Geophysical Journal International, 166(1), 485-492. https://doi.org/10.1111/j.1365-246X.2006.03021.x
 Vinciguerra, S., Trovato, C., Meredith, P. G., Benson, P. M., Troise, C., & de Natale, G. (2006). Understanding the seismic velocity structure of Campi Flegrei caldera (Italy): From the laboratory to the field scale. Pure and Applied Geophysics, 163(10), 2205-2221. https://doi.org/10.1007/s00024-006-0118-y
 Schubnel, A., Benson, P. M., Thompson, B. D., Hazzard, J. F., & Young, R. P. (2006). Quantifying damage, saturation and anisotropy in cracked rocks by inverting elastic wave velocities. Pure and Applied Geophysics, 163(5-6), 947-973. https://doi.org/10.1007/s00024-006-0061-y
 Benson, P. M., Schubnel, A., Vinciguerra, S., Trovato, C., Meredith, P., & Young, R. P. (2006). Modeling the permeability evolution of microcracked rocks from elastic wave velocity inversion at elevated isostatic pressure. Journal of Geophysical Research: Solid Earth, 111(4). https://doi.org/10.1029/2005JB003710
 Vinciguerra, S., Trovato, C., Meredith, P. G., & Benson, P. M. (2005). Relating seismic velocities, thermal cracking and permeability in Mt. Etna and Iceland basalts. International Journal of Rock Mechanics and Mining Sciences, 42(7-8 SPEC. ISS.), 900-910. https://doi.org/10.1016/j.ijrmms.2005.05.022
 Benson, P. M., Meredith, P. G., Platzman, E. S., & White, R. E. (2005). Pore fabric shape anisotropy in porous sandstones and its relation to elastic wave velocity and permeability anisotropy under hydrostatic pressure. International Journal of Rock Mechanics and Mining Sciences, 42(7-8 SPEC. ISS.), 890-899. https://doi.org/10.1016/j.ijrmms.2005.05.003
 Benson, P. M., Meredith, P. G., & Platzman, E. S. (2003). Relating pore fabric geometry to acoustic and permeability anisotropy in Crab Orchard Sandstone: A laboratory study using magnetic ferrofluid. Geophysical Research Letters, 30(19). https://doi.org/10.1029/2003GL017929
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- Jan. 2012 to present: Reader in Rock Physics, Rock Mechanics Laboratory, University of Portsmouth, U.K.
- Nov. 2010 to present: Honorary research Fellow, Rock and Ice Physics Laboratory, University College London, U.K.
- Jan. 2010 to Aug. 2010: Postdoctoral Fellow, McGill University, Montreal, Canada.
- Sept. 2009 to Dec. 2009: Research Associate (visiting professor), Experimental volcanology laboratory, Ludwig-Maximilians-Universitšt, Munich, Germany.
- April 2005 to Aug. 2009: EU Marie-Curie Research Fellow in rock physics, Lassonde Institute of Engineering Geoscience, University of Toronto, Canada.
- 2004: Ph.D. in Geophysics, Dept. Earth Sciences, University College London, U.K.
- 1998: M.Sc. in Exploration Geophysics (1998), School. of Earth Sciences, University of Leeds, U.K.
- 1997: M.Phys. Physics with Astrophysics (1997), Dept. of Physics and Astronomy, Leicester University, U.K.
* Member, NERC peer review college (2012-present).
* Postgraduate tutor (School of Earth Sciences: 2015-2020).
* Editorial board, Tectonophysics (Elsevier). http://www.journals.elsevier.com/tectonophysics/editorial-board/
* Editorial board, Royal Society Open Science. https://royalsocietypublishing.org/rsos/editorial-board/
* Academic co-representative, EPOS board of national scientific representatives for the UK.
See my full ORCID profile here: https://orcid.org/0000-0003-2120-3280
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