Posts by Collection
El Mayor-Cucapah (Mw 7.2) earthquake: Early near-field postseismic deformation from InSAR and GPS observations
Published in Journal of Geophysical Research: Solid Earth, 2014
El Mayor-Cucapah earthquake occurred on 4 April 2010 in northeastern Baja California just south of the U.S.-Mexico border. The earthquake ruptured several previously mapped faults, as well as some unidentified ones, including the Pescadores, Borrego, Paso Inferior and Paso Superior faults in the Sierra Cucapah, and the Indiviso fault in the Mexicali Valley and Colorado River Delta.We conducted several Global Positioning System (GPS) campaign surveys of preexisting and newly established benchmarks within 30 km of the earthquake rupture. We show that the near-field GPS and InSAR observations over a time period of 5 months after the earthquake can be explained by a combination of afterslip, fault zone contraction, and a possible minor contribution of poroelastic rebound.
Recommended citation: Gonzalez-Ortega, A., Fialko, Y., Sandwell, D., Nava-Pichardo, F. A., Fletcher, J., Gonzalez-Garcia, J., Lipovsky, B. P., Floyd, M. A., and Funning, G. (2014). " El Mayor-Cucapah (Mw 7.2) earthquake: Early near-field postseismic deformation from InSAR and GPS observations " Journal of Geophysical Research: Solid Earth. 119. http://bradlipovsky.github.io/files/Gonzalez-Ortega2014.pdf
Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation
Published in Journal of Geophysical Research: Solid Earth, 2015
Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide.
Recommended citation: Lipovsky, B. P., and E. M. Dunham (2015). " Vibrationalmodes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation " Journal of Geophysical Research: Solid Earth. 120. http://bradlipovsky.github.io/files/LipovskyDunham2015.pdf
Published in The Cryosphere, 2016
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.
Recommended citation: Lipovsky, B. P. and Dunham, E. M. (2016). "Tremor during ice-stream stick slip 2." The Cryosphere. 10. http://bradlipovsky.github.io/files/LipovskyDunham2016.pdf
Published in Science Advances, 2016
The Greenland ice sheet presently accounts for ∼70% of global ice sheet mass loss. We demonstrate that small variations in seismic wave speed in Earth’s crust, as measured with the correlation of seismic noise, may be used to infer seasonal ice sheet mass balance.
Recommended citation: Mordret, A., Mikesell, T. D., Harig, C., Lipovsky, B. P., & Prieto, G. A. (2016). " Monitoring southwest Greenland’s ice sheet melt with ambient seismic noise." Science advances, 2(5), e1501538. http://bradlipovsky.github.io/files/mordret2016.pdf
Slow-slip events on the Whillans Ice Plain, Antarctica, described using rate-and-state friction as an ice stream sliding law
Published in Journal of Geophysical Research: Earth Surface, 2017
The Whillans Ice Plain (WIP), Antarctica, experiences twice daily tidally modulated stick-slip cycles. Slip events last about 30 min, have sliding velocities as high as ∼0.5 mm/s (15 km/yr), and have total slip ∼0.5 m. Slip events tend to occur during falling ocean tide: just after high tide and just before low tide. To reproduce these characteristics, we use rate-and-state friction, which is commonly used to simulate tectonic faulting, as an ice stream sliding law.
Recommended citation: Lipovsky, B. P. and Dunham, E. M. (2017). "Slow-slip events on the Whillans Ice Plain, Antarctica, described using rate-and-state friction as an ice stream sliding law 3." Journal of Geophysical Research: Earth Surface. 122. http://bradlipovsky.github.io/files/LipovskyDunham2017.pdf
Published in Journal of Geophysical Research: Oceans, 2018
Distant storms, tsunamis, and earthquakes generate waves on floating ice shelves. Previous studies, however, have disagreed about whether the resulting wave-induced stresses may cause ice shelf rift propagation. Most ice shelf rifts show long periods of dormancy suggesting that they have low background stress concentrations and may therefore be susceptible to wave-induced stresses. Here I quantify wave-induced stresses on the Ross Ice Shelf Nascent Rift and the Amery Ice Shelf Loose Tooth T2 Rift using passive seismology.
Recommended citation: Lipovsky, B. P. (2018). "Ice Shelf Rift Propagation and the Mechanics of Wave-Induced Fracture" Journal of Geophysical Research: Oceans. 123. http://bradlipovsky.github.io/files/Lipovsky2018.pdf
Dynamics of the Askja caldera July 2014 landslide, Iceland, from seismic signal analysis: precursor, motion and aftermath
Published in Earth Surface Dynamics, 2018
Landslide hazard motivates the need for a deeper understanding of the events that occur before, during, and after catastrophic slope failures. Here, we use data from a network of 58 seismic stations to characterise a large landslide at the Askja caldera, Iceland, on 21 July 2014.
Recommended citation: Schöpa, A., Chao, W. A., Lipovsky, B. P., Hovius, N., White, R. S., Green, R. G., & Turowski, J. M. (2018). "Dynamics of the Askja caldera July 2014 landslide, Iceland, from seismic signal analysis: precursor, motion and aftermath." Earth Surface Dynamics, 6(2). http://bradlipovsky.github.io/files/schopa2018.pdf
Published in Science, 2019
Stearns and van der Veen (Science, 20 July 2018, p. 273) conclude that fast glacier sliding is independent of basal drag (friction), even where drag balances most of the driving stress. This conclusion raises fundamental physical issues, the most striking of which is that sliding velocity would be independent of stresses imparted through the ice column, including gravitational driving stress.
Recommended citation: Minchew, B. M., Meyer, C. R., Pegler, S. S., Lipovsky, B. P., Rempel, A. W., Gudmundsson, G. H., Iverson, N. R., (2019). "Comment on “Friction at the bed does not control fast glacier flow” " Science. 363. http://bradlipovsky.github.io/files/Minchew2019.pdf
Published in Annals of Glaciology, 2019
Subglacial hydrology exerts a significant control on glacier flow. Despite this importance, it is inherently difficult to observe processes at the glacier bed. Therefore numerous studies either concentrate on point measurements directly at the glacier bed through boreholes, or on recordings of signals emitted from hydraulic events acquired with passive seismic techniques. These recordings often show resonances, whose interpretation is challenging (Clarke, 2005; Podolskiy and Walter, 2016). Some studies attribute similar resonance observations in other geological contexts to an intrinsic resonance of hydraulic fractures (Aki and others, 1977) while other studies explain such observations as wave propagation effects (Bean and others, 2014). Here, we explore these mechanics using observations from a kHz-sampled pressure sensor installed in a borehole directly above the hard granite bedrock of a temperate mountain glacier in Switzerland. Our borehole observations confirm the occurrence of both sound and crack waves within the basal water layer.
Recommended citation: Graff, D., Walter, F., Lipovsky, B. P. (2019). " Crack wave resonances within the basal water layer" Annals of Glaciology. 79. http://bradlipovsky.github.io/files/Graff2019.pdf
Published in Annals of Glaciology, 2019
The evolution of glaciers and ice sheets depends on processes in the subglacial environment. Shear seismicity along the ice–bed interface provides a window into these processes. Such seismicity requires a rapid loss of strength that is typically ascribed to rate-weakening friction, i.e., decreasing friction with sliding or sliding rate. Many friction experiments have investigated glacial materials at the temperate conditions typical of fast flowing glacier beds. To our knowledge, however, these studies have all found rate strengthening friction. Here, we investigate the possibility that rate-weakening rock-on-rock friction between sediments frozen to the bottom of the glacier and the underlying water-saturated sediments or bedrock may be responsible for subglacial shear seismicity along temperate glacier beds.
Recommended citation: Lipovsky, B. P., Meyer, C. R., Zoet, Z. K. , McCarthy, C., Hansen, D. D., Rempel, A. W., Gimbert, F. (2019). "Glacier sliding, seismicity, and sediment entrainment" Annals of Glaciology. 79. http://bradlipovsky.github.io/files/Lipovsky2019.pdf
Published in Geophysical Research Letters, 2019
Understanding deformation in ice shelves is necessary to evaluate the response of ice shelves to thinning. We study microseismicity associated with ice shelf deformation using 9 broadband seismographs deployed near a rift on the Ross Ice Shelf. From December 2014 - November 2016, we detect 5948 icequakes generated by rift deformation. Ocean swell, infragravity waves and a signicant tsunami arrival do not affect seismicity. Instead, seismicity correlates with tidal phase on diurnal timescales and inversely correlates with air temperature on multi-day and seasonal timescales. Spa tial variability in tidal elevation tilts the ice shelf, and seismicity is concentrated while the shelf slopes downward toward the ice front. During especially cold periods, thermal stress and embrittlement enhance fracture along the rift. We propose that thermal stress and tidally-driven gravitational stress produce rift seismicity with peak activity in the winter.
Recommended citation: Olinger, S. D., D. A. Wiens, B. P. Lipovsky, R. C. Aster, A. A. Nyblade, R. A. Stephen, P. D. Bromirski, P. Gerstoft, Z. Chen (2019). " Tidal and Thermal Stresses Drive Seismicity along a Major Ross Ice Shelf Rift" Geophysical Research Letters Accepted May 17, 2019. http://bradlipovsky.github.io/files/Olinger2019.pdf
Graduate course, Harvard University, Department of Earth and Planetary Sciences, 2018
An introduction graduate course that explores the physics of glaciers and ice sheets
Informal reading group, Harvard University, Department of Earth and Planetary Sciences, 2019
A low-key reading group that meets about twice per month in the summer to discuss recent progress in all areas of glaciology.
Undergraduate field experience, Harvard University, Department of Earth and Planetary Sciences, 2019
A week long fieldtrip to Iceland that emphasizes tectonics, glaciology, volcanology, climate, and Earth history.
Graduate course, Harvard University, Department of Earth and Planetary Sciences, 2019
An graduate course that explores applications of machine learning in a variety of EPS disciplines.