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Geubelle, Philippe H.; Breitenfeld, Michael

doi:10.1023/a:1007498300031

Cited by 42 publications

(17 citation statements)

References 23 publications

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“…The relationship between surface velocities and hydraulic fracture resonance, in contrast, is not as clear. Finally, simple models of hydraulic fracture resonance (Lipovsky and Dunham, 2015) and turbulent channel flow (Gimbert et al, 2014) predict spectral signatures that are not consistent with the evenly spaced spectral peaks observed on the WIP, although complex geometrical effects may invalidate the simplifying assumptions of such models. These distinguishing criteria may be useful in analyzing several recently described data sets (Heeszel et al, 2014;Helmstetter et al, 2015a, b;Hammer et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

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Tremor during ice stream stick-slip

Lipovsky¹,

Dunham²

2015

Preprint

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Abstract. During the 200 km-scale stick slip of the Whillans Ice Plain (WIP), West Antarctica, seismic tremor episodes occur at the ice–bed interface. We interpret these tremor episodes as swarms of small repeating earthquakes. The earthquakes are evenly spaced in time and this even spacing gives rise to spectral peaks at integer multiples of the recurrence frequency ~ 10–20 Hz. We conduct numerical simulations of the tremor episodes that include the balance of forces acting on the fault, the evolution of rate- and state-dependent fault friction, and wave propagation from the fault patch to a seismometer located on the ice. The ice slides as an elastic block loaded by the push of the upstream ice, and so the simulated basal fault patch experiences a loading velocity equal to the velocity observed by GPS receivers on the surface of the WIP. By matching synthetic seismograms to observed seismograms, we infer fault area ~ 10 m2, bed shear modulus ~ 10 MPa, effective pressure ~ 10 kPa, and state evolution distance ~ 1 μm. Large-scale slip events often occur twice daily, although skipped events have been increasing in frequency over the last decade. We observe that tremor seismic particle velocity amplitudes are greater during the double wait time events that follow skipped events. The physical mechanism responsible for these anomalously high seismic amplitudes may provide a window into near-future subglacial conditions and the processes that occur during ice stream stagnation.

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Section: Discussionmentioning

confidence: 99%

“…Tremor episodes in glaciers may also be related to the motions of fluids contained within conduits (Métaxian et al, 2003;Stuart et al, 2005;Winberry et al, 2009;Gimbert et al, 2014;Lipovsky and Dunham, 2015;Bartholomaus et al, 2015). Several lines of evidence suggest that the WIP tremor episodes are not related to such a source process.…”

Section: Discussionmentioning

confidence: 99%

Tremor during ice stream stick-slip

Lipovsky¹,

Dunham²

2015

Preprint

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“…where V is the spatially averaged sliding velocity on the patch surface, t is time, and the radiation damping parameter is (Geubelle and Breitenfeld, 1997) …”

Section: The Elastic Responsementioning

confidence: 99%

Tremor during ice-stream stick slip

Lipovsky¹,

Dunham²

2016

The Cryosphere

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Abstract. During the 200 km-scale stick slip of the Whillans Ice Plain (WIP), West Antarctica, seismic tremor episodes occur at the ice-bed interface. We interpret these tremor episodes as swarms of small repeating earthquakes. The earthquakes are evenly spaced in time, and this even spacing gives rise to spectral peaks at integer multiples of the recurrence frequency ∼10-20 Hz. We conduct numerical simulations of the tremor episodes that include the balance of forces acting on the fault, the evolution of rate-and statedependent fault friction, and wave propagation from the fault patch to a seismometer located on the ice. The ice slides as an elastic block loaded by the push of the upstream ice, and so the simulated basal fault patch experiences a loading velocity equal to the velocity observed by GPS receivers on the surface of the WIP. By matching synthetic seismograms to observed seismograms, we infer fault patch area ∼10 m 2 , bed shear modulus ∼20 MPa, effective pressure ∼10 kPa, and frictional state evolution distance ∼1 µm. Large-scale slip events often occur twice daily, although skipped events have been increasing in frequency over the last decade. The amplitude of tremor (recorded by seismometers on the ice surface) is greater during the double wait time events that follow skipped events. The physical mechanism responsible for these elevated amplitudes may provide a window into nearfuture subglacial conditions and the processes that occur during ice-stream stagnation.

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“…We have reported a method 17 to calculate the critical effective pressure () for icequakes:here η = radiation damping parameter 69 …”

Section: Methodsmentioning

confidence: 99%

Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

et al. 2019

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Fluctuations in glacier motion are very common and are thought to be controlled by subglacial hydrology and till deformation. There are few instrumented studies that have monitored seasonal changes. We use the innovative Glacsweb subglacial in situ wireless probes, combined with dGPS and custom geophone data from an Icelandic soft-bedded temperate glacier, to show that there are two distinct seasonal styles of speed-up events. Relatively small diurnal events occur during the melt season, whilst during winter there are larger multi-day events related to positive degree days. These events are accompanied by a distinct pattern of till deformation and basal icequakes. We argue these reflect stick-slip motion which occurs when the glacier hydrological system is unable to accommodate the melt water flux generated by surface melt episodes. We show a rare fully instrumented coupled glacier/till record of contrasting summer and winter stick-slip motion and discuss its implication for till sedimentology.

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Cited by 42 publications

References 23 publications

Tremor during ice stream stick-slip

Tremor during ice stream stick-slip

Tremor during ice-stream stick slip

Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology

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