Details of Award
NERC Reference : NE/P012507/1
Using small events to constrain the physical mechanism governing slow slip
Grant Award
- Principal Investigator:
- Dr JC Hawthorne, University of Oxford, Earth Sciences
- Grant held at:
- University of Oxford, Earth Sciences
- Science Area:
- Earth
- Overall Classification:
- Panel A
- ENRIs:
- Environmental Risks and Hazards
- Science Topics:
- Plate tectonics
- Seismic hazards
- Seismicity
- Subduction
- Tectonic modelling
- Tectonic Processes
- Earthquakes
- Seismicity
- Subduction zones
- Tectonic systems
- Geohazards
- Earthquakes
- Faulting
- Abstract:
- In conventional models, faults can slip in one of two ways: steadily at rates near plate rate or episodically in earthquakes. However, in the past two decades researchers have discovered another behaviour: slow slip events. In slow slip events, large portions of the plate interface slip accelerate periodically but then stall long before reaching seismic slip rates. The puzzle is why: what physical mechanism allows for slow yet episodic slip? Episodic slow slip is important to understand because slow slip events occur just below the locked zone, which hosts hazardous megathrust earthquakes. Constraints on slow slip can help us constrain how the earthquake-generating region is loaded to failure. Slow slip may even help us understand how large earthquakes start, as the physics governing the beginning of slow slip is likely the same physics that governs the beginning of large earthquakes. Slow slip is also important because it is abundant. M>6 events have been observed on most well-instrumented subduction zones, accommodating large fractions of the plate interface slip at depth. If we are to understand the seismic cycle and the stress state at subduction ones, we need to understand slow slip. A number of physical mechanisms have been proposed to explain slow slip. And a number of these models have reproduced the slow yet episodic slip, usually by allowing for complications in the fault rheology or spatial variations in the fault properties. However, these models have not appeared capable of reproducing all the properties of observed slow slip events. Specifically, the models are designed to be slow and relatively stable, so they struggle to reproduce the complexity that is increasingly observed within a slow slip event. It thus seems that we need a new or modified model. The challenge is that there are many plausible models to consider. So in this project, I propose to evaluate several models and to identify several model properties that are essential to reproducing observed slow slip. To better evaluate these models, I propose to compare them with existing observations of large slow slip events as well as new analysis of data from the more numerous small slow slip events in central Cascadia. Several tens of small slow slip events occur annually in Cascadia. They are accompanied by seismic tremor: low-amplitude, sustained seismic vibrations thought to be composed of numerous tiny earthquakes driven by the slow slip event. We will track the tremor locations, so that we can see how the small slow slip events grow in space. In addition, we will estimate the magnitude of aseismic slip in the small events, using the unique network of high-precision PBO borehole strainmeters in Cascadia. We will use these new analyses to evaluate several numerical models of slow slip and constrain essential model characteristics.
- NERC Reference:
- NE/P012507/1
- Grant Stage:
- Completed
- Scheme:
- Standard Grant FEC
- Grant Status:
- Closed
- Programme:
- Standard Grant - NI
This grant award has a total value of £323,743
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DA - Estate Costs | DI - Staff | DA - Other Directly Allocated | DI - T&S |
|---|---|---|---|---|---|---|
| £6,585 | £126,888 | £22,866 | £43,382 | £111,775 | £3,710 | £8,536 |
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