britgeophysics

Bullerwell Lecture 2018 at EGU

Dr Tom Mitchell (UCL) gives this year’s Bullerwell Lecture at the European Geosciences Union (EGU) meeting in Vienna at 7 pm on Thursday 12 April, in room 2.15 of the Austria Centre.

The Bullerwell Lecture is the British Geophysical Association’s prestigious named lecture awarded to an early-career UK-based geophysicist.

 

We hope to see many people there.

Bullerwell Lecture 2018 title

Earthquake fracture damage and healing: feedback on rupture dynamics

Abstract

The importance of the damage zone in the faulting and earthquake process is widely recognized, but our understanding of how damage zones are created, what their properties are, and how they feed back into the seismic cycle, is remarkably poorly known. Firstly, damaged rocks have reduced elastic moduli, cohesion and yield strength, which can cause attenuation and potentially non-linear wave propagation effects during ruptures. Secondly, damaged fault rocks are generally more permeable than intact rocks, and hence play a key role in the migration of fluids in and around fault zones over the seismic cycle. Finally, the dynamic generation of damage as the earthquake propagates can itself influence the dynamics of rupture propagation, by increasing the amount of energy dissipation, decreasing the rupture velocity, modifying the size of the earthquake, changing the efficiency of weakening mechanisms such as thermal pressurisation of pore fluids, and even generating seismic waves itself. On top of this, instantaous reductions in crustal seismic velocity following earthquakes has been used to infer dynamic damage, but a growing body of geophysical evidence exists for ‘healing’ processes occurring in the crust following such earthquakes, inferred from time-dependent increases in seismic velocity lasting from days to years. All of these effects imply that a feedback exists between the damage imparted immediately after rupture propagation, at the early stages of fault slip, and the effects of that damage on subsequent ruptures dynamics. As such, investigating the relative contributions of individual ruptures to cumulative off-fault damage is critical to fully understand the earthquake energy budget.
In recent years, much debate has been sparked by the identification of so-called ‘pulverized rocks’ described on various crustal-scale faults, a type of intensely damaged fault rock which has undergone minimal shear strain, and the occurrence of which has been linked to damage induced by transient high strain-rate stress perturbations during earthquake rupture. Damage induced by such transient stresses, whether compressional or tensional, likely constitute heterogeneous modulations of the remote stresses that will impart significant changes on the strength, elastic and fluid flow properties of a fault zone immediately after rupture propagation, at the early stage of fault slip.
In this contribution, I will present high resolution datasets of fault zone co-seismic damage patterns from the micro- to km-scale, on several active and inactive crustal scale fault zones. This damage has been quantified using state of the art damage analysis techniques, from CT scanning at the microscopic scale, to using drones and photogrammetry/structure-from-motion to produce high resolution macroscopic structure, damage and alteration maps both along strike and perpendicular to major active and inactive fault structures. Depth and subsurface extent of this damage is then constrained by gravitmetric surveys, magenetotellurics and seismological techniques. In this context, I will then demonstrate and discuss laboratory and field examples of coseismic mechanisms that induce pulverization through dynamic modulations in stress, acting as energy sinks during earthquakes and the feedbacks on rupture dynamics

New Advances in Geophysics meeting 2018

Joint meeting of the BGA and NSGG

WHEN: 1st-2nd February 2018

WHERE: RAS, Burlington House, London

CLICK HERE TO SUBMIT AN ABSTRACT

Geophysical answers to global security challenges

In an ever changing and evolving political environment, global security will remain at the forefront of international discourse for many years to come. High-resolution monitoring, timely assessment and accurate interpretation of security-relevant events in the geosphere will be vital for building and maintaining trust between peoples and nations. The application and development of a diverse range of geophysical techniques to this global challenge is the focus of the 2018 New Advances in Geophysics (NAG) conference, which will be jointly organised by the British Geophysical Association and the Near Surface Geophysics Group of the Geological Society.

Evolution of new technologies and threats, and advances in covert operations mean that we need novel methods of monitoring the geosphere, and intelligent ways of analysing and interpreting geophysical data. There is a diverse toolbox of techniques that we, as a scientific community, can use to address relevant questions and issues:

  • Global seismic monitoring and numerical modelling of nuclear explosions and other events of interest
  • Satellite-based geophysical monitoring of sites of interest
  • Development of UAV-borne geophysical survey platforms for challenging and unsafe environments
  • Application of archaeogeophysical methods to site inspections
  • Environmental impacts of testing and storage of nuclear, chemical, biological and conventional weapons
  • Application of industry techniques such as 4D seismics to model changes in subsurface characteristics following underground explosions
  • Many more…

On behalf of the BGA and the NSGG, the conveners invite you to contribute papers on this theme to the 2018 NAG meeting. We also welcome contributions with a different scientific focus, but which use methods or techniques that may have potential for application to this topic.

 

2017 PGRiP winners

 

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Congratulations to our 2017 PGRiP presentation winners:

Best Talk

1st Oliver Sanford (Durham) “Modelling Seismic Wave Propagation and Scattering within Extrusive Basalt Sequences”

2nd Alistair Boyce (Imperial) “Insights into the Tectonics of the Eastern North American Shield at the Macro-scale: A new Absolute P-wave Tomographic Model for North America”

Best Poster

1st Guy Paxman (Durham) “Lithospheric Flexure in East Antarctica: the Origin and Evolution of the Transantarctic Mountains and Wilkes Subglacial Basin”

2nd Daniel Possee (Southampton) “Seismicity and Local Earthquake Tomography from Haiti”

New Year Honour for Professor Willy Aspinall

Congratulations to Professor Willy Aspinall, Cabot Professor in Natural Hazards and Risk Science at the University of Bristol, who was appointed a companion to the Order of St Michael and St George for his services to the Government and community in Montserrat in the New Year Honours. More details here: http://www.bristol.ac.uk/news/2016/december/willy-aspinall.html

2016 PGRiP winners

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Congratulations to our 2016 PGRiP presentation winners

Best Talk

1st Adam Robinson – Durham

Construction and Subduction of the Louisville Ridge Seamount Chain – Insights from Wide-Angle Seismic Imaging

2nd Rebecca Coats – Liverpool

Lava dome eruptions: testing the strain rate dependence of porous lava rheology

 

Best Poster

1st Jennifer Jenkins – Cambridge

Converted phases from sharp mid-mantle heterogeneity beneath Western Europe

2nd Aude Lavayssiere – Southampton

Imaging lithospheric discontinuities using S to P receiver functions

 

EAGE Erasmus award 2016

Congratulations to Anton Ziolkowski for winning this year’s  EAGE Erasmus award!

Details on the award and Dr Ziolkowski’s work can be found here on the EAGE website.

PDR Position – Durham

WHAT?

Postdoctoral Researcher on modelling global volatile cycling and mantle dynamics

WHERE?

Durham

BY WHEN?

21st May 2016

DETAILS:

We seek a postdoctoral researcher with geodynamical modelling experience to study the volatile exchange between the deep Earth and the exosphere and the related secular evolution of mantle dynamics using spherical numerical 3D mantle dynamics models.

This post is part of a NERC funded consortium on “The Feedback Between Volatiles and Mantle Dynamics”, which includes team members from UCL, Liverpool, Manchester, Leeds, and Durham. The aim of this consortium is to understand the role of water and other volatiles on the mantle dynamics of the Earth and the operation of plate tectonics through time. This consortium is one of three funded consortia on “Volatiles, Geodynamics & Solid Earth Controls on the Habitable Planet”. More information on the consortia is available at http://www.deepvolatiles.org.

The postdoctoral research position will be full-time, fixed term (3 years), based at Durham University, UK, with summer 2016 as preferred start date. The successful applicant will closely collaborate with several team members of the consortium, in particular Dr Jeroen van Hunen (Durham) and Prof Carolina Lithgow-Bertelloni (UCL), and will interact with the other consortia members in NERC’s Deep Volatile Programme.

The closing date for applications is 21st May 2016. Further job details and application information can be found via http://www.earthworks-jobs.com/geoscience/durham16042.html . For any further questions, please contact me atjeroen.van-hunen@durham.ac.uk.

Post-Graduate Newsletter

Check out the new edition of the Post-Graduate Newsletter here.

Geophysics profiles – the life of a freelance geophysicist

Check out the next geophysics profile!

https://britgeophysics.org/richard-bowen-freelance-exploration-geophysicist/

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Geophysics profiles – the life of an exploration mining geophysicist

Check out the next geophysics profile!

https://britgeophysics.org/sarah-harvey-exploration-geo-2/

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