NSFGEO-NERC Earthquake nucleation versus episodic slow slip: what controls the mode of fault slip?
Lead Research Organisation:
University of Liverpool
Department Name: Earth, Ocean and Ecological Sciences
Abstract
Earthquakes, produced by rapid slip on faults, account for the majority of deaths from a range of natural disasters which amounts to about 60,000 people a year worldwide - around 90 percent of which occur in developing countries. Slip can occur in three ways on faults. These are (1) earthquake slip; (2) stable fault creep driven by plate tectonic loading rates; and (3) episodic slow slip events, where fault slip spontaneously accelerates but never reaches earthquake slip speeds. Episodic slow slip events can release the same amount of energy as earthquakes but over days to weeks rather than seconds to minutes. They most commonly occur in certain regions of subduction zones and have been linked to elevated pore pressures. These three modes of fault slip are vital to understand, as episodic slow slip and fault creep relieve stress build up and reduce seismic hazard, yet also transfer stress from one part of the fault to another, ultimately affecting the nucleation of destructive earthquakes.
In this project, we will provide physical constraints from combined experiments and numerical modelling to determine the controlling factors leading to stable fault creep, episodic slow slip, or earthquakes. As yet, it is not understood what puts the brakes on some instabilities creating slow fault slip yet allows others to accelerate to rapid slip speeds that cause earthquakes. A transition of some sort from unstable frictional sliding (typically viewed as leading to earthquakes) to stable frictional sliding (typically viewed as leading to fault creep) while the sliding velocity is increasing must promote sustained slow slip on faults. The nature of this stability transition is widely debated and the range of conditions under which it may occur are ill defined. We will investigate the key hypotheses proposed to explain such stability transition and the resulting slow slip events, which include (1) evolution in friction properties related to very slow slip rates at elevated temperatures, (2) the role of pore fluid pressure on stability transitions, where small increases in pore volume of the granular shearing material in the fault produces a large decrease in pore pressure resulting in increase in the shear resistance (dilatant strengthening), and (3) spatial variation in fault properties and conditions leading to a situation where nucleation of an earthquake can occur but is limited by adjacent regions with stable frictional properties.
The work will involve integrated laboratory experiments and numerical modelling. Controlled lab experiments will measure the evolution of fault friction under previously unexplored temperature, pore fluid pressure, and slip rate conditions relevant to natural faults. We will quantify the evolution of frictional properties from very slow, tectonic fault slip rates of millimetres per year, to those through the episodic slow slip range of millimetres per day, and into the slip rates of meters per second where earthquakes occur. Fluid pressure changes promoted by compaction and dilation during slip will also be characterized. Numerical modelling of the experiments at the laboratory scale will help to ensure that the coupled physical mechanisms involved are understood and captured in our mathematical descriptions. The large-scale behaviour of faults with the properties defined by the experiments will be explored by numerical modelling at the scale of natural faults. The numerical modelling will relate the experimental findings to field observations of episodic slow slip and earthquake nucleation and investigate the role of spatial variations in fault properties on the occurrence of episodic slow slip events vs. earthquakes. A key deliverable for this work would be identification of the range of fault conditions and physical mechanisms under which episodic slow slip, fault creep, or earthquakes can occur, leading ultimately to improved seismic hazard forecasting.
In this project, we will provide physical constraints from combined experiments and numerical modelling to determine the controlling factors leading to stable fault creep, episodic slow slip, or earthquakes. As yet, it is not understood what puts the brakes on some instabilities creating slow fault slip yet allows others to accelerate to rapid slip speeds that cause earthquakes. A transition of some sort from unstable frictional sliding (typically viewed as leading to earthquakes) to stable frictional sliding (typically viewed as leading to fault creep) while the sliding velocity is increasing must promote sustained slow slip on faults. The nature of this stability transition is widely debated and the range of conditions under which it may occur are ill defined. We will investigate the key hypotheses proposed to explain such stability transition and the resulting slow slip events, which include (1) evolution in friction properties related to very slow slip rates at elevated temperatures, (2) the role of pore fluid pressure on stability transitions, where small increases in pore volume of the granular shearing material in the fault produces a large decrease in pore pressure resulting in increase in the shear resistance (dilatant strengthening), and (3) spatial variation in fault properties and conditions leading to a situation where nucleation of an earthquake can occur but is limited by adjacent regions with stable frictional properties.
The work will involve integrated laboratory experiments and numerical modelling. Controlled lab experiments will measure the evolution of fault friction under previously unexplored temperature, pore fluid pressure, and slip rate conditions relevant to natural faults. We will quantify the evolution of frictional properties from very slow, tectonic fault slip rates of millimetres per year, to those through the episodic slow slip range of millimetres per day, and into the slip rates of meters per second where earthquakes occur. Fluid pressure changes promoted by compaction and dilation during slip will also be characterized. Numerical modelling of the experiments at the laboratory scale will help to ensure that the coupled physical mechanisms involved are understood and captured in our mathematical descriptions. The large-scale behaviour of faults with the properties defined by the experiments will be explored by numerical modelling at the scale of natural faults. The numerical modelling will relate the experimental findings to field observations of episodic slow slip and earthquake nucleation and investigate the role of spatial variations in fault properties on the occurrence of episodic slow slip events vs. earthquakes. A key deliverable for this work would be identification of the range of fault conditions and physical mechanisms under which episodic slow slip, fault creep, or earthquakes can occur, leading ultimately to improved seismic hazard forecasting.
People |
ORCID iD |
Daniel Faulkner (Principal Investigator) |
Publications
Bedford JD
(2022)
Fault rock heterogeneity can produce fault weakness and reduce fault stability.
in Nature communications
Lambert V
(2021)
Scale Dependence of Earthquake Rupture Prestress in Models With Enhanced Weakening: Implications for Event Statistics and Inferences of Fault Stress
in Journal of Geophysical Research: Solid Earth
Ashman I
(2023)
The Effect of Clay Content on the Dilatancy and Frictional Properties of Fault Gouge
in Journal of Geophysical Research: Solid Earth
Tal Y
(2022)
The Effect of Fault Roughness and Earthquake Ruptures on the Evolution and Scaling of Fault Damage Zones
in Journal of Geophysical Research: Solid Earth
Bedford J
(2021)
The stabilizing effect of high pore-fluid pressure along subduction megathrust faults: Evidence from friction experiments on accretionary sediments from the Nankai Trough
in Earth and Planetary Science Letters
Description | Panel member to write proposal for NERC call |
Geographic Reach | National |
Policy Influence Type | Participation in a guidance/advisory committee |
Impact | A £5M NERC and Nuclear Waste Services call arose from the scoping document our committee wrote. The funded project will provide essential scientific data that contribute towards UK's future energy security and also help communication to the public about the eventual siting of a Geological Disposal Facility that is based on sound scientific research. |
URL | https://www.ukri.org/opportunity/derisking-geological-disposal-of-radioactive-waste-in-the-uk/ |
Description | FY2022 JSPS Invitational Fellowships for Research in Japan (Short-term) |
Amount | ¥850,000 (JPY) |
Funding ID | S22037 |
Organisation | Japan Society for the Promotion of Science (JSPS) |
Sector | Public |
Country | Japan |
Start | 08/2022 |
End | 09/2022 |
Title | Identifying steady state to correctly determine frictional rate and state parameters |
Description | We have developed the ideas, and wrote the code, for properly identifying steady state in rock friction data to allow the correct determination of frictional rate and state parameters that are crucial for understanding and predicting the earthquake nucleation phase. |
Type Of Material | Data analysis technique |
Year Produced | 2023 |
Provided To Others? | Yes |
Impact | None yet |
Description | Caltech earthquake modelling |
Organisation | California Institute of Technology |
Country | United States |
Sector | Academic/University |
PI Contribution | We are combining experimental constraints to earthquake rupture models to understand the behaviour of large earthquakes. My part of the collaboration is to provide experimental and field expertise. |
Collaborator Contribution | Modelling expertise. |
Impact | Currently working on several papers. The result of previous collaborations was this NERC-NSF award. |
Start Year | 2016 |
Description | Herdman Symposium, Liverpool |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Schools |
Results and Impact | Invited talk to the annual Herdman Symposium 2022, a gathering of Schools, general public. We had participants from several countries and 6 invited speakers. |
Year(s) Of Engagement Activity | 2022 |
Description | Radio Interview |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Media (as a channel to the public) |
Results and Impact | Interview with Radio Merseyside on the Turkey/Syria earthquake in February 2023. |
Year(s) Of Engagement Activity | 2023 |
URL | https://www.bbc.co.uk/sounds/play/p0dyf1lm |
Description | Radio interview |
Form Of Engagement Activity | A press release, press conference or response to a media enquiry/interview |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Media (as a channel to the public) |
Results and Impact | Radio interview with BBC Radio Essex on a small earthquake that occurred near Colchester. |
Year(s) Of Engagement Activity | 2023 |
Description | Talk to the University of the Third Age, Loughborough, UK, November 2021 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | Talk on 'Carbon capture and storage' to the University of the Third Age, Loughborough, UK, November 2021. ~60 people attended online. |
Year(s) Of Engagement Activity | 2022 |