| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | June 10, 2015 |
| Latest Amendment Date: | June 2, 2017 |
| Award Number: | 1520760 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2015 |
| End Date: | June 30, 2020 (Estimated) |
| Total Intended Award Amount: | $395,000.00 |
| Total Awarded Amount to Date: | $395,000.00 |
| Funds Obligated to Date: |
FY 2016 = $114,263.00 FY 2017 = $136,634.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
201 OLD MAIN UNIVERSITY PARK PA US 16802-1503 (814)865-1372 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
522 Deike Building University Park PA US 16802-1503 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Geophysics |
| Primary Program Source: |
01001617DB NSF RESEARCH & RELATED ACTIVIT 01001718DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Earthquakes represent a sudden release of elastic energy that is stored in the rocks adjacent to tectonic faults, driving catastrophic failure. In normal (fast) earthquakes the rupture zone expands at a few kilometers per second, and fault slip rates reach 1 to 10 meters per second. However, tectonic faults also fail in slow earthquakes with rupture durations of months or more and fault slip speeds of a of small fraction of an inch per second or less. Recent work shows that tectonic faults fail in spectrum of slip modes that includes slow earthquakes, normal (fast) earthquake, and many other forms of slip. These slow modes of slip can transfer stress to the fast earthquake zone and potentially trigger damaging, normal earthquakes. However, we know very little about the mechanics of slow earthquakes. This research effort will address questions such as: what determines the rupture speed of slow earthquakes? A central element of this work is carefully conducted laboratory studies of repetitive, slow stick-slip events with continuous measurement of acoustic emission, elastic wave speed and amplitude, and fault zone friction behavior. Hypotheses to be tested include: 1) does slow slip failure represents prematurely arrested normal (fast) slip for a range of materials and 2) can the same fault zone can host slow and fast slip behaviors.
Slow earthquakes are one form of transient fault slip that may load seismogenic portions of fault zones and abet damaging earthquakes. The origin of slow earthquakes and related forms of transient fault slip is poorly understood. The project will take a systematic approach to investigate: 1) the underlying processes of slow slip, with focus on the frictional mechanisms and continuum coupling that may explain the spectrum of fault slip behaviors in nature, 2) microstructural studies of the laboratory samples to assess how shear localization and strain distribution compare between normal (fast) and slow stick-slip, and 3) acoustic measurement of fault zone elastic properties, with particular focus on precursors to failure. The proposed study will extend the analogy between frictional stick-slip and normal (fast) earthquakes to include slow slip events. The results will provide insight on the mechanics of slow earthquakes and other forms of quasi-dynamic fault slip. All data and results obtained will be published in peer-reviewed journals and made available via public websites.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Outcomes of a project funded by the US National Science Foundation
Federal Award ID: EAR-1520760
The Spectrum of Fault Slip Behaviors and the Mechanics of Slow Earthquakes
C. Marone (Penn State University)
This project was a systematic investigation of the physics of slow earthquakes, with particular focus on the mechanical processes that dictate the slip speed and propagation velocity of slow ruptures. Laboratory and theoretical studies were designed to address: 1) the underlying processes of slow slip, with focus on the frictional mechanisms and continuum coupling that may explain the spectrum of fault slip behaviors in nature, 2) microstructural studies of the laboratory samples to assess how shear localization and strain distribution compare between normal (fast) and slow stick-slip, and 3) acoustic measurement of fault zone elastic properties, with particular focus on precursors to failure. We worked to evaluate the well known connections between frictional stick-slip (lab earthquakes) and ordinary (fast) earthquakes and to extend the analogy between lab earthquakes and the spectrum of tectonic faulting styles from slow slip events to slow earthquakes and ordinary earthquakes. The results have provided significatn insight into the mechanics of slow earthquakes and other forms of quasi-dynamic fault slip.
We published a total of 41 papers and an equal/larger number of meeting abstracts. We gave over a dozen talks at national meetings and we helped researchers in other labs learn the techniques necessary to study slow earthquakes in the lab.
We improved our understanding of precursors to lab earthquakes and discovered that mean stress dependent changes in fault zone elastic properties can mask the changes that occur prior to failure.
We discovered that previous work, dating back to 1992, on the effects of fault normal stress on fault strength had missed an important effect related to fault slip velocity and frictional state (memory effects). The results have major implications for the use of acoustic waves to monitor fault contact area and strength.
The project supported 5 graduate students who developed skills for computation, data collection and analyis, technical skills for laboratory work, communication skills and the presentation and writing skills that come with presenting and publishing scientific research.
Our work is described in a number of publications, including the following. Most of these are freely available. Anyone who would like access to others should contact Chris Marone at marone@psu.edu
- Bolton, D. C., Shreedharan, S. Rivière, J., and C. Marone, C, Acoustic energy release during the laboratory seismic cycle: insights on laboratory earthquake precursors and prediction, J. Geophys. Res. Solid Earth, 125, 10.1029/2019JB018975, 2020.
- Im, K., Saffer, D. M., Marone, C. and J. P. Avouac, Slip rate-dependent friction as a universal mechanism for slow slip events, Nature Geosc., 2020.
- Kenigsberg, A. R., Rivière, J., Marone, C. and D. M. Saffer, Evolution of elastic and mechanical properties during fault shear: the roles of clay content, fabric development, and porosity. J. Geophys. Res. Solid Earth, 10.1029/2019JB018612, 2020.
- Kenigsberg, A. R., Rivière, J., Marone, C. and D. M. Saffer, A method for determining absolute ultrasonic velocities and elastic properties of experimental shear zones, Int. J. Rock Mech. and Min. Sci., 30,10.1016/j.ijrmms.2020.104306, 2020.
- Shreedharan, S., Bolton, D. C., Rivière, J., and C. Marone, Preseismic fault creep and elastic wave amplitude precursors scale with lab earthquake magnitude for the continuum of tectonic failure modes, Geophys. Res. Lett., e2020GL086986, 2020.
- Veedu, D. M., Giorgetti, C., Scuderi, M. M., Barbot, S., Marone, C., and C. Collettini, Bifurcations at the stability transition of earthquake faulting, Nature Geosc., 2020.
- Kenigsberg, A. R., Rivière, J., Marone, C. and D. M. Saffer, The effects of shear strain, fabric, and porosity evolution on elastic and mechanical properties of clay- rich fault gouge, J. Geophys. Res. Solid Earth, 10.1029/2019JB017944, 2019.
- Bolton, D. C., Shokouhi, P., Rouet-Leduc, B., Hulbert, C., Rivière, J., Marone, C., and P. A. Johnson, Characterizing acoustic precursors to laboratory stick-slip failure events using unsupervised machine learning, Seis. Res. Letts., 10.1785/0220180367, 2019.
- Fisher, D. M., Smye, A. J., Marone, C., van Keken, P. E., and Yamaguchi, Kinetic models for healing of the subduction interface based on observations of ancient accretionary complexes, Geochem. Geophys. Geosyst., GGGE21954, 10.1029/2019GC008256, 2019.
- Hulbert, C., Rouet-Leduc, B., Johnson, P. A., Ren, C. X., Rivière, J., Bolton, D. C., and C. Marone, Machine learning predictions illuminate similarity of fast and slow laboratory earthquakes, Nat. Geosc., 12, 69-74, 10.1038/s41561-018-0272-8, 2019.
- Im, K., Marone, C. and D. Elsworth, The transition from steady frictional sliding to inertia-dominated instability with rate and state friction, J. Mech. Phys. Sol., 122, 116-125, 10.1016/j.jmps.2018.08.026, 2019.
Last Modified: 09/03/2020
Modified by: C. J. J Marone
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