| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | July 2, 2010 |
| Latest Amendment Date: | July 2, 2010 |
| Award Number: | 0944198 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2010 |
| End Date: | June 30, 2014 (Estimated) |
| Total Intended Award Amount: | $35,002.00 |
| Total Awarded Amount to Date: | $35,002.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
3720 S FLOWER ST FL 3 LOS ANGELES CA US 90033 (213)740-7762 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
3720 S FLOWER ST FL 3 LOS ANGELES CA US 90033 |
| 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: |
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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
Many fundamental questions in earthquake physics remain unresolved, largely because of
difficulties in obtaining high-quality, near-source recordings of small earthquakes and
deriving reliable source parameters. The overarching goal of this project is to provide an
improved understanding of earthquake source processes for a wide magnitude range
(approximately -4 to 4). We are performing detailed seismological investigations of
source properties that characterize several distinct classes of seismic events (earthquakes,
rockbursts, and blasts) in a 3.6 km deep South African mine. We will also conduct a short
field campaign to record seismic events at the extremes of the magnitude range and in
close proximity to fault structures. Full source tensor inversions, second moment
analysis, and spectral methods will be used to determine comprehensive sets of source
properties including scalar potencies/moments, focal mechanisms, corner frequencies,
strain/stress drops, radiated energies, rupture velocities, and source time functions.
Special effort will be devoted to detecting isotropic components of faulting. Theoretical
calculations of expected radiation from different event types will help in the
interpretation of results.
Applying the above analysis to the small-magnitude, near source seismic data will allow
us to obtain constraints on many aspects of earthquake physics including nucleation
processes, the prevalence of isotropic components of seismic radiation, changes in the
physics of rupture with event magnitude or with proximity to geologic and mining
structures, and source parameter differences between earthquakes, explosions, and other
seismic sources. The high-resolution results on seismic source properties and scaling
relations will significantly impact the earthquake physics and rock mechanics
communities by helping to resolve long-term controversies on earthquake nucleation and
rupture processes, scaling of laboratory results to natural faults, and earthquake energy
budgets, among others. In addition, the findings on spatially dependent seismic properties
will be useful for decision-making concerning when and where to suspend mining
activities to enhance underground safety
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.
This project provided support to investigate earthquake source processes for a wide magnitude range, using newly developed techniques and detailed seismological analyses of source properties. The studies involved the following research directions: (1) Analysis of radiated seismic energy of P and S waves generated by small earthquakes in a deep gold mine, South Africa. The obtained results suggest that the majority of events display a significant tensile component and some may also include damage-related radiation. (2) Developing an improved method for inversion of seismic waveforms to full source tensor properties. This is done by decomposing a general seismic source tensor into isotropic tensor, double-couple tensor and compensated linear vector dipole using the eigenvectors and eigenvalues of the full tensor. Two dimensionless parameters are used to quantify the size of the isotropic and compensated linear vector dipole components. The parameters have well-defined finite ranges and are suited for non-linear inversions of source tensors from seismic waveform data. (3) Developing and using methods for detecting signatures of damage-related radiation by observing isotropic components of source tensors and enhanced P radiation at high frequency waves. The studies provided one PhD student and one young researcher with state-of-the-art techniques for analyzing earthquake source properties. Three peer-reviewed papers were published in prime seismological journals.
Last Modified: 07/08/2014
Modified by: Yehuda Ben-Zion
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